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Choosing a lathe for woodturning

It’s easy to get it wrong when choosing a lathe. That can greatly restrict the work you can do, or prevent you enjoying woodturning, the very thing you are buying it for. There are so many machines on the market, some of such poor quality that they can only be used for very light work. How do you choose between them?

To perform well, a lathe must be designed well and made well. Top quality doesn’t come cheap, but even inexpensive machines can be compared when choosing a lathe to see which is the better buy. Good quality lathes last indefinitely and often a used one is a better choice than a poor quality new one, even if you have to replace bearings or scrape off a bit of rust or change the motor from three phase to single phase.

Few suppliers advertise that their lathes are of poor quality, so you have to make up your own mind which is best. You can consult other turners, but when you are choosing a lathe, it’s your money. The best approach is to make sure you understand what makes a good machine. When you have examined lathes from different price ranges you will see the differences and be able to make an informed choice.

The perfect lathe  does not exist, and never will, because so much of the design of a lathe involves compromises. For example,  a short bed lathe takes up less space and is easier to use, but will limit the length you can turn. Nor is there such a thing as a beginner’s lathe or starter lathe. Either a lathe is a good one or it isn’t, and a beginner is not well served by a poor quality machine that causes problems in use. You can compromise on size or variable speed if cost is important. But don’t compromise more than you have to on build quality. Weak components and poor manufacturing tolerances may make the lathe almost unusable for anything but very light work.

Here is a checklist.

Size

The first thing to consider when choosing a lathe is size. A big lathe is the most versatile, as although you can do small work on a large machine, the opposite does not apply. Many of my bowls could have been made on a small lathe, but not all. Bigger lathes, made primarily for more experienced turners, are also usually of better quality. The biggest can still do small work, though they sometimes cumbersome. For example the toolrest holder and tailstock will be heavy to move.

But if you have limited space or budget, a good small machine will be fine for small work, and the better ones are very capable. The smallest machines, micro lathes, should only be considered if you have a particular need for one, for example if easy portability is critical. Even if you only want to make very small items, a larger machine will probably be easier to use. Drill-powered lathes are also unsuitable for general use, because of their light construction and the noise they make.

Rigidity

When choosing a lathe and comparing machines, look for:

  • a strongly constructed headstock with a large diameter headstock spindle, mounted in heavy-duty bearings that are well separated. The spindle nose thread should have a wide register at the back to support the chuck butting against it. Except on small lathes, the spindle should accept number 2 or larger morse tapers.
  • a strongly made tailstock,  that on bigger lathes can accept number 2 or larger morse tapers
  • a robust tool rest and support
  • a substantial and rigid bed
  • a strong and stable stand or bench that will support the lathe without shaking.

Look for key components made of cast iron or heavy welded steel. Cast aluminium, thin pressed steel or light weight tubular components may not be rigid enough, and heavily stressed screw threads in aluminium can wear rapidly.

Cast iron or steel bed?

It is often said that cast iron is the best material for lathe beds because it suppresses vibration, and there is some truth in this. Lathes with flimsy, light weight beds made of pressed steel are really only suitable for light work. Steel tube beds or solid steel bars can flex and vibrate, but the heavier and stronger (and shorter) they are, the better the lathe will be. Cast iron can be brittle, so is usually made quite thick and heavy out of necessity, which tends to be a good thing. A heavy cast iron bed with good cross-linking webs connecting the sides will be the foundation for a good machine.

But some top end lathes have steel beds. Heavy steel plate is welded to a heavy steel tube, round or square. The assembly is large enough to prevent twisting and flexing. Vibration on these is not a problem.

The tool rest and holder

When choosing a lathe, pay particular attention to the design of the tool rest and its holder (sometimes known as the banjo). These are key components and any weakness will prevent smooth, chatter-free cutting, particularly when using scrapers. This is specially important if the lathe has a swivel headstock as you may have to extend the holder far off the bed. The greater the overhang, the stronger the components needed to resist flexing under load. Some may bend or even break if the tool catches. Avoid rest holders with lightweight jointed swing arms. If the holder has a cam lock, it needs a heavy and rigid eccentric spindle, otherwise the clamping force will vary depending on where the holder is. Access for adjusting the tension should be easy. The hole for the toolrest stem should be deep as this will help prevent it flexing under load.

The toolrest itself should be heavy and strong in proportion to its length, with a large diameter stem. But the most heavily built rest will flex if it is too long and only has a single stem. You need a robust rest but one with a narrow top, to put the fulcrum for the tools close to the wood, minimizing tool projection. A flat top to the rest hinders proper tool movement because there are two distinct pivot points when tilting the tool.

Grip

Many turners like to use an underhand grip to anchor the tool and improve control, so the shape of the rest should allow you to grip the underside with your fingers (though some sacrifice this for the sake of greater strength, and many turners prefer the overhand grip). The rest holder and locking levers must not obstruct tool movement, when the handle is low. For this reason, it is good to have alternative positions for the stem locking lever. The side of the rest that faces you should be steep, so the tool handle can drop low enough anywhere along the rest, including directly over the stem.

The lathe should have a short and a long rest as well as the standard, as all are useful. The long one may need a second rest holder. The rest should be capable of being positioned as close as possible to the lathe axis so tool projection on thin spindles is minimised, and should be easy to move.

Tool rests can be replaced if necessary.

Weight

A heavy lathe shakes less when spinning an unbalanced piece of wood. Weight comes from strong and rigid cast iron/steel construction. The stand or bench that the machine sits on must also be strong and heavy,  but it may be possible to add weights to the stand to improve stability. The lathe will be more stable if it stands on a concrete floor.

Construction quality

Machines with strong and heavy components are usually OK. But there are some points worth checking when choosing a lathe.

  • Make sure that the spindle and motor pulleys have keys fitted into slots to secure them. Some makers rely on grub screws alone, which work loose and become a constant annoyance.
  • All-over machining of the pulleys will help them run smoothly, without vibration. Check that pulleys align properly.
  • Choosing a lathe with poor quality headstock spindle bearings, power switch, electronic variable speed controller and motor can lead to trouble later. Look for components of a recognised brand, not the cheapest that the maker could find. You want them fully enclosed to keep dust and chips out, and the motor fan cooled and rated to run continuously. Cheap motors run hot.
  • See that the top surface of the bed is smooth and true. A bed with a flat top may be easier if you want to fit accessories such as a steady rest. Be sure that the headstock and tail stock can line up accurately with each other. Any apparent error could be due to an uneven floor causing the bed to twist slightly, and easily corrected.
  • Make sure there is no detectable play in the tailstock ram when extended and locked. Also that the tailstock slides freely but locks immovably to the bed. The revolving tail centre must have no play in its bearings when under load (this is a replaceable item).
  • Make sure that the headstock spindle has no play or end float – fit the faceplate and see if it will move.
  • Make sure also that the tool rest holder and the tool rest itself move freely and lock immovably at all positions. Some will lock when close to the lathe axis but not when further out.
  • The screw threads that lock the toolrest and tailstock ram should be generous in size and snug-fitting. The points of the locking screws should not cut into the metal. The handles should be strong and preferably of steel, not plastic.
  • Poor paintwork and sharp edges on the castings suggest a lack of attention to detail at the factory.

Choosing a lathe for ease of use

It’s important to consider ergonomics when choosing a lathe. Good ones are designed for ease of use, and fit your particular needs. Look for spanner-free adjustments. See that the locking levers don’t get in the way (particularly the one that locks the toolrest stem – try it with the holder in different positions). Make sure that they are robust. Plastic levers will break in time. Levers adjustable for angle are useful. It should be easy to remove the tool rest holder from the lathe. Ideally this should be possible without removing the tailstock or dismantling anything.

If you are choosing a lathe primarily for making bowls and boxes, you may find it much better to be able to work from the front of the piece without having to bend over the lathe bed. A shortbed lathe, or one with a swivel or sliding headstock or with outboard turning provision lets you do this (though short bed lathes obviously sacrifice capacity, and you never know what lengths you may want to turn in future). But other turners are happy to work over the bed and don’t mind bending. A swivel or sliding headstock also prevents obstruction of the tools when the handles hit the lathe bed.

There should be an indexing arrangement for a swivel headstock so you can quickly return it to parallel. It is possible for debris to get under a swiveling or sliding headstock, affecting its rigidity and alignment. This could affect the tailstock too. I have not found this a problem in the lathes I have owned, but good design would minimise the risk. In particular, the headstock should not tilt when you loosen it. As long as it sits flat on the bed it will be difficult for chips to get between the metal surfaces.

When turning spindles, you will need to get close to the work. Make sure there is no obstruction to your feet that will force you to bend forward. If on a bench stand, the lathe should be well to the front, as consistent with stability. A gap underneath for your toes is good, though it will accumulate shavings.

The height of the lathe spindle is important if you use it for hours at a time. The usual rule is to have the axis at, or a little above elbow height. Then you don’t have to bend. But it depends on the individual. You may have to experiment to find the most comfortable height for you. Some lathe stands are adjustable for height. But it is normally possible to raise the lathe on blocks or to stand on a platform when working.

The headstock spindle and tailstock ram are best hollow. This allows you to use a knock out bar, and you can drill long holes on the lathe.  It’s nice if the tailstock taper is self-ejecting. An easy and effective spindle lock for the headstock is important so you can remove chucks. Provision for dividing is useful for some work. But the division holes should not double as the spindle lock, unless they and the locking pin are substantial. Otherwise the holes will soon wear.

A headstock handwheel that lets you turn the spindle is useful when inspecting  the work or winding on chucks. The tailstock handwheel should be generous in size and operate freely. A place to keep calipers, sandpaper etc is useful. There is often a flat top on the headstock for this. You also need somewhere to fix adjustable lights. But these aren’t necessarily on the lathe.

Unless you know you will not need to turn pieces bigger than the capacity over the bed, when choosing a lathe go for one with provision for outboard turning. Or one with a sliding or swivel headstock. You can use a freestanding tool rest, but they are often unsatisfactory. Unless they are rigidly locked to the lathe, they can tilt or bend inwards, causing a catch. Sliding headstocks and outboard toolrests may need more space in use. You need access to the ends of the bed and you may have to remove the tailstock. The tailstock cannot be used with a sliding headstock when it is moved right to the end of the bed. Nor when the headstock swivels.

Motor power

Choosing a lathe with insufficient power will slow you down. A 1/3 horsepower motor is about the minimum for a small lathe. It will do for small spindle work and for small bowls when cuts are light. Under-powered lathes stall easily, which is annoying. One horsepower will do for medium size bowls. It is enough for large ones if you use the low-speed pulley setting and take light cuts. Two to three horsepower will let you work at a natural pace on large pieces without stalling the motor. Large motors may need permanent wiring rather than just a domestic style plug and socket. Large motors are less safe for a beginner, because they can apply a lot of force to the tools.

Noise

The lathe itself should run quietly, though when cutting there will be more noise. You will soon tire of rattles and bearing noise. The lathe should have an induction motor, not one with brushes and gears. The drive belt should not be tensioned solely by the weight of the motor. This can cause it to bounce, which can lead to noise and vibration. To avoid this, there should be a lock for the motor. The motor should, ideally, be directly below the spindle to minimise shaking.

Speeds

When choosing a lathe, look for one with a good range of lathe speeds. Low speeds, preferably down to 200 rpm or less, are more important than high. This is because it is unsafe to spin unbalanced chunks of wood fast even on a heavy machine. If the wood is sound, balanced, secure and not too large, turning at higher speeds is usually best. But you will get used to whatever maximum speed your lathe has. Many lathes these days have electronic variable speed, and this is a great feature. Even more so if it goes down to zero and can reverse the lathe. The very low rpm you can get from a good variable speed unit can be useful. It helps if you want to apply finishes to work while it is still on the lathe or to sand green-turned bowls.

But step pulleys work well, provided that it is easy to adjust the speed. It should not be necessary to go behind or underneath the machine, unlock covers or use spanners. Even with good quality electronic variable speed, it is very useful to have step pulleys. This is because their lower speed settings give more torque. You can often upgrade a lathe to electronic variable speed, but at significant cost. Some lathes have mechanically variable speed, with lever-operated cone pulleys. I have little experience of these, but they may be unreliable unless well made, and may cause rapid wear on the belt. The unit on the lathe at my turning club has not held up well. Adjustment is only possible when the lathe is running.

Accessories

Make sure the lathe is ready to accept headstock and tailstock accessories. Choosing a lathe with a non-standard spindle nose thread will make it hard to find chucks. Avoid machines that do not allow use of Morse taper fittings in both headstock and tailstock.

 

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Homemade long tool rest

A homemade long tool rest can be a useful accessory. It’s a great help if the tool rest is longer than the spindle you are turning by at least 25 mm at each end. This extra length gives tool access to the ends of the spindle, and it’s much easier to turn sweeping curves accurately if you don’t have to keep moving a short tool rest. Lathes don’t usually come with a very long tool rest as standard. One can often be bought as an accessory, at substantial cost. Over a certain length, a long rest needs two stems to keep it rigid and stop chatter.

It’s quite easy to put together a homemade long tool rest and a second holder to support it using hardwood. A wooden tool rest is pleasant to use, and was standard in past times. You will need to remove the sharp side edges on skew chisels to protect the wood. But that’s necessary for steel rests too. If the rest gets a lot of use, you may have to plane or sand the top smooth from time to time. If thought necessary, a metal strip or bar could be fixed on top with epoxy.

The stems

Make the two stems of round steel bar. One needs to fit your existing tool rest holder. The other can be any size because you will drill the holder to fit. The length should bring the top of the rest to the proper height when in the wooden holder.

I made mine by drilling a hole in one end of each bar. I used a tapping drill that matched a bit of threaded rod. The rod was tight in the hole so it would stay secure. Inserting the rod about 25 mm deep and projecting about the same distance seemed about right.

More simply, you could just glue the stems into holes about a quarter of the way along from each end of the wooden rest. The main thing is to make sure the stems are parallel to each other and securely held in the wood.

The rest

My homemade long tool rest began life as an oak table leg, about 600 mm long, 40 mm thick and 50 mm deep. I find it quite strong enough. I planed the front to make a slope.

The holder (banjo)

Use hardwood, say 60 mm thick, and drill a blind hole, say 45 mm deep, at one end for the second stem. Wood will probably not be strong enough to take a locking screw that will bear on the stem and hold it firmly, so that limits height adjustment. You could make a saw cut in the holder and put in a clamping bolt to squeeze it and make it pinch the stem. A second bolt would be needed on the opposite side of the stem This would reinforce the holder and stop it splitting when tightening the clamp. Or you could just put a spacer in the hole under the stem to raise it a little.

Saw a slot in the holder that will fit over a clamping screw to hold it on the lathe bed.

A steel version of this holder could have a locking screw to allow easier height adjustment.

The clamp

Now make a clamping block that will fit your lathe bed. Its design will vary because all lathes are different. Mine is made of thick MDF and fits between the ways. It has a projecting lip underneath. A bolt passes through the block and is long enough to reach up through the wooden holder. A washer and nut clamps the holder in place on the bed.

homemade long tool rest
Homemade long tool rest

Plan of homemade long tool rest

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Harden steel using these simple methods

It’s sometimes useful to know how to harden steel. Although it’s possible to do woodturning with very few tools, I can never resist trying something new. Sometimes I buy tools, but often I make them myself. Back in the days before commercial tools were available, turners knew how to harden steel and temper it. They made their own tools out of high carbon steel, or got them from the local blacksmith. The best way to harden steel and temper it is to do it properly by modern methods. This requires the right steel for the job, with careful control of temperatures and timing and the rates of heating and cooling. But acceptable results can usually be obtained using the cruder methods described here.

Tool steel

Turning tools are now rarely manufactured from carbon steel, but it is still used for many other purposes. Even for turning tools, it still works as well as it did when the old-time turners made their living with it. You can buy high carbon steel in various grades from steel stockholders, some suitable for hardening in water and others in oil.

Scrap carbon steel is easy to find. If you want to harden steel for tool making, springs, files, saw blades, masonry nails, crow bars, cold chisels, woodworking chisels, old screwdrivers, plane irons and many other things are steel that is suitable for reworking. I have used the tines of an old garden fork and the rings from old ball races. Keep in mind that if you put the tool under significant stress, steel that has or may develop cracks is unsuitable. For example, the valleys between the teeth of a file are weak points where cracks can start.

If you are using scrap, old steel is often the best choice because some modern steel alloys may not respond well to these basic heat treatment procedures. One way to tell what you’ve got is to touch the steel on a grinder. Lots of bright bursting sparks like a child’s ‘sparkler’ firework mean it is probably high carbon steel. Try a bit of mild steel such as an ordinary nail for comparison. It will also make a lot of sparks, but there will be fewer bursters. The use of the metal before it became scrap is a clue – if it was subject to a lot of stress, the metal is probably high carbon steel. But there is a continuum of carbon content – to be sure, test-harden a piece before making the tool.

Low carbon mild steel

Ordinary low-carbon mild steel is not suitable for most cutting tools. You cannot harden steel of that kind, and it will not keep a sharp edge. To harden steel, the metal must have a high enough carbon content. The metal is harder than wood, and a cutting edge on mild steel may last long enough for a one-off job. But if the edge is thin it will just give way under pressure. You can case-harden mild steel. This gives it a very thin layer of higher carbon content on its surface. Then you can use it for some light-duty cutting tools provided you don’t grind away the hardened skin when sharpening. To case-harden, coat the metal with a special compound before heating. You can use mild steel as a holder for inserted or brazed-on cutters.

Equipment needed

To harden steel, you must first make it hot. You can use a magnet to check that it is hot enough for hardening – when the magnet stops attracting it, the steel is ready. More simply, just get it red hot, which is also the temperature needed for hot forging. The bigger the piece, the more heat you will need. If the item is small, you can harden steel using a burner on a gas cooker. You can use a charcoal fire with a blower to supply air.  You can do a lot with a reasonably powerful blowtorch. Larger pieces of steel may dissipate the heat as fast as it is applied, never getting hot enough. If using a blowtorch, you can stack a few dry bricks to make an enclosure to retain the heat.

A simple forge burning solid fuel or propane is not hard to improviseThere is video on YouTube about making a simple but very effective propane forgeI made a forge that burned anthracite and worked 7/8 inch bar without too much trouble. More recently I made a propane forge using just two insulating fire bricks and a blowtorch, and was able to bend steel strip of about 2 inches width and 3/8 inches thick.

Hot forging

If you make two pieces of steel white hot, you can weld them together by hammering. Hotter still, the metal will burn and spoil. But these temperatures are harder to reach with the sort of equipment described.

If you want to do any hot forging, you will need something to use as an anvil, a hammer, vise and heavy pliers. You may also need a hacksaw, angle grinder, file, bench grinder and a drill press. To work thick steel, you will need heavier tools and a forge.  If it’s hot enough, it’s surprisingly easy to bend steel using a vise or wrenches, or to hammer it into shape on an anvil. You can forge ordinary mild steel in the same way.

Annealing

Some scrap carbon steel is too hard for sawing or filing into shape. You will have to anneal it to make it softer and workable. To do this, the first step is to make the metal red hot. While it is hot, you can forge it. Don’t try to work the metal when it has lost its red heat or it may crack. You have to strike while the iron is hot. After any forging, get the steel red hot again and then anneal it by cooling it slowly. The slower it cools, the better – traditionally the metal was left to cool buried in hot ashes. If using a propane forge, you can just leave the metal to cool in the forge so the residual heat will slow the cooling. You want the whole piece uniformly softened, so try to heat and cool it evenly.

When cooled, the annealed steel should be soft enough to file. Check that all parts are soft, then carry out whatever further operations you need. Shape the tool, including rough grinding the edge.

Harden the steel

To harden steel, heat the part to be hardened bright red hot again, if possible ‘soak’ it in the heat for a bit, then quench it. It’s the rapid change from red hot to cold that will harden steel. You can use various quenching liquids, but a bucket of water will usually do the trick. Plunge the red hot metal straight in, and swirl it about to cool it as rapidly as possible. If the steel warps or cracks when quenched, try using oil instead of water, or use different steel. If using oil, fire precautions are necessary. Use a metal container, not a plastic bucket. The hot steel will heat and ignite the oil, so have a metal cover handy to extinguish the flames.

You don’t always have to harden all parts of a tool to the same degree. If it must withstand stress in use, you can leave the bulk of it soft, for toughness and strength, with just the cutting tip hardened.

After quenching, the steel should be glass-hard and a file will just slide off it without cutting. Don’t try too hard with the file, the hard metal will soon make it blunt.

Tempering

The freshly hardened tool will be brittle. If you were to use it in this state, the edge could chip or it could shatter. For most purposes, you must heat it one more time to temper it before use. Tempering takes away the brittleness. It makes the metal tougher, but softer. The higher the temperature reached during tempering, the softer and less brittle the steel will become. Each tool has its own optimum compromise between hardness and toughness.

Before tempering, clean up the metal using abrasives. You want the steel bright and shiny for this stage. Warm the tool very carefully above, not in, a clean flame. Watch the bright metal surface carefully as it heats up. Let the heat start away from the edge and creep towards it, aiming for a uniform temperature over the surface. The edge and any other thin parts will heat up too fast if exposed to the heat directly.

Watch the colour change

As it gets hotter, you will see the bright steel change colour. It will go from silvery to a pale yellow, through brown to blue and then to grey. You have to catch the moment when the colour you want reaches the edge. Normally a pale yellow-brown colour at the edge of a cutting tool is about right for cutting wood, but different tools may need other colours. A blue colour will leave the steel tough and strong, but not hard enough to keep a cutting edge. (Springs are tempered to blue, and some steel components such as screws are blued for decorative purposes.)

Don’t let it get too hot

If you let the metal get too hot you will have to repeat the hardening stage. You can repeat the annealing, hardening and tempering without harm to the metal. But too long at high temperature can tend to burn out the carbon from the surface layers. When the colour is right, quench the tool again. It is then ready for final clean up and sharpening before being put to use.

Sometimes you need more accurate tempering, for example if you need a larger piece evenly tempered. You can do this by heating the item in an oven at a set temperature, or in oil. You will need a thermometer for these methods. They allow for soaking at the proper temperature, which may give better results.

 

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Hazards in a woodturning workshop

There are some significant hazards in a woodturning workshop. Some of them are specific to turning and others are common to all woodworking. The hazards that can cause ill health and injuries in industrial workplaces are just as much an issue for hobby turners. Perhaps more so, as the law provides some protection for people at work, including in the UK a requirement for adequate information, instruction, supervision and training to be provided to employees. Amateurs working alone may only discover the dangers the hard way, which is a good reason to go on a turning course.

But we can take precautions, and most turners survive with nothing more than minor scratches from time to time. The risks are manageable if recognised. An absorbing occupation that helps keep you active has health benefits too. Turning is fun, and perhaps no more dangerous than other kinds of woodworking. And what activity is completely hazard-free?

Careful working

Some of the risks can be minimised by obvious safety rules such as keeping guards on machines and wearing face protection. Often, people ignore these rules and just work carefully. It’s their choice. But it’s hard to be careful all the time, and probably most people who get hurt thought they would be OK as long as they were careful. There are some hazards that can’t be eliminated, so only being careful will protect you against them – for example you have to avoid getting your fingers caught between the spinning wood and the tool rest on the lathe. Care, alertness and good working habits are always going to be necessary, and they become second nature.

Dust

All turners know that dust is one of the hazards, but often aren’t sure how dangerous it is. Turners are exposed to dust concentrations significantly higher than the safety standards set for industrial workers. But few are exposed for eight hours a day, every day, the assumption behind those standards. Only a small proportion of hobby turners are likely to suffer serious harm.

Dust control is achieved in the turning workshop by effective collection at source, with a breathing mask if the extraction fails to capture all the dust. For more information, see my articles on wood dust and dust control.

Machinery and turning

Spinning wood can badly injure or even kill people. If spinning too fast, it can break up. The pieces will then fly with all the kinetic energy given to them by the lathe motor. A key left in the chuck when the lathe is switched on will be flung out. An incorrectly presented tool can dig in, wrenching the wood as well as perhaps throwing the tool.

If the timber is not secure, it can come loose and hit someone, but while it remains in one piece, much of its kinetic energy is rotational. You don’t want it hitting you, but if it does, the force of impact will usually be less than the hammer blow you could receive from half of a large bowl blank. An unbalanced piece run too fast can tear itself off the chuck with significant sideways momentum. If the fixing is secure, the forces could overturn the lathe.

Sharp edges on the rotating timber can cut. The rotating drive centre or chuck, and the workpiece, can entangle hair or clothing, pulling you in with great and sudden force. Something will have to give, and that’s a battle the lathe will win. Rags or steel wool wrapped round your fingers can drag them in. Projecting chuck jaws can trap your fingers against the tool rest or send a sharp cutting tool flying. The hollow Morse taper in the headstock will grab anything put into it, including a finger. The lathe’s drive belt could easily break your fingers against the pulley. A wrongly presented cutting tool catching in the wood and snapping down onto the toolrest can pinch fingers. A Jacobs chuck can work loose from the spindle taper and perhaps be flung across the shop.

Other machines

Turners typically use other machinery, including a bandsaw, chain saw, grinder, sander, drill, table saw and others, all with their own specific hazards. These machines may have rotating cutters and parts that can entangle hair or clothing, or finger trapping points (for example between a grinding wheel and its tool rest).

Risk control

Tie back long hair when using any machinery with exposed rotating parts. Don’t wear long sleeves, a tie, a scarf, loose clothing or jewelry that might catch. Don’t take chances with a poorly gripping chuck or a weak fixing on a faceplate. Keep the lathe speed down when turning heavy pieces, particularly when they are not balanced – always check the speed before switching on. If something goes wrong, the lower the lathe speed, the less will be the consequences. If the lathe has variable speed it can be good practice to use the speed control to stop the lathe rather than the off switch. This avoids starting at a high speed set for the last job.

Don’t use timber with dangerous cracks or bark inclusions or rotted areas. Keep out of the ‘line of fire’ if possible, particularly when starting up. Make sure the off switch is within reach. Take off the sharp edge on a bowl rim with a tool or abrasive. Don’t use a chuck with projecting jaws. Never put your finger into the taper while the lathe is running. Move the toolrest out of the way when sanding. Use paper instead of rag when polishing, and don’t wrap steel wool round your finger.

Never leave the chuck key in the chuck. Handle cutting tools with care around the spinning wood to avoid accidental contact, and don’t have your finger between the tool and the toolrest.

Learn to walk before you run

Don’t turn large heavy pieces until you have plenty of experience of smaller ones. Some lathes have steel mesh guards to stop flying chunks of wood. Wear good quality full face protection, properly adjusted – chips can fly up under a face shield and get in your eyes, unpleasant at the least. Don’t use gloves if they might catch. (If flying chips hurt your hands, reduce the speed or put a chip deflector on the gouge. If your hands are cold, turn the heating up.) And if using a Jacobs chuck without tailstock support, fit a draw bar to keep it secure.

Understand the equipment

Make sure you understand the machines, their hazards, and good practice in their use (for example the danger of kickback on a table saw is not immediately obvious to a beginner). Be cautious when taking advice from a YouTube video which is not from an authoritative source. Don’t use the machines beyond their safe limits. Keep guards in place when the machines are in use, and use appropriate personal protective equipment. Full face protection is advisable at the lathe – safety glasses are not sufficient.

Bandsawing timber for woodturning has some particular hazards. For example, cross-cutting round timber can cause the blade to grab and bind. This can jerk your hands into the blade or crush your fingers between the wood and the saw table. It is best to hold the timber with a clamp to stop it rolling into the blade. Any blank without support under the point of the cut can tilt into the blade. Sawing spalted wood can sometimes be a problem. You may be pushing the wood into the saw when the blade enters a soft patch and the wood suddenly shoots forward. Never push with your hand in line with the blade. When cutting discs, you may also find the wood shoots forward suddenly when the blade comes out of cut after sawing off the corner of the blank.

Electricity

Fatal electrocutions are rare, causing only a small percentage of industrial deaths. But electric shocks that fail to kill are much more common. Whether a shock is fatal often comes down to luck – it depends on whether there is a low resistance path for the current to earth. If, for example, you are standing on a wet concrete floor or have your hand on a machine that is earthed, more current will pass through your body, and it may kill you.

Ensure that all wiring and appliances are in sound condition. Check flexes and plugs from time to time. Use an earth leakage device that will disconnect the power in the event of a shock. Don’t use unsuitable electrical equipment in damp conditions. Don’t use makeshift, substandard wiring or ‘temporary’ unsafe fittings.

Falls

Slips and trips are the commonest causes of injury in the workplace.

Keep the floor clear of trip hazards and anything slippery, and keep the working area well lit. Don’t climb on makeshift steps or unstable platforms from which you could fall. Repair any holes in the floor. Don’t let cables and hoses trail across the floor. Clear up off-cuts. A floor can become slippery as the surface wears, or if oil finish, wax polish (or wax sealer from turning  blanks, a particular problem) or sawdust gets on it, so may need attention. Don’t forget the route to the workshop. If you have to go down an unlit garden path with icy patches and steps, it’s only a matter of time before gravity gets you.

Heavy objects

Chucks and bowl blanks, and sharp tools can easily cause serious foot injuries if dropped. Keep working areas tidy so that chucks etc. are less likely to fall. Have a good place to keep tools when they are waiting for use – don’t just perch the skew chisel on the vibrating lathe bed. Wear shoes with steel toecaps.

Manual handling

Back strains caused by lifting are extremely common. Moving logs or machinery can injure you. The risk does not just depend on the weight of the object; other factors are relevant too. For example, if workshop clutter forces you to move awkwardly when you pick up a large bowl blank. Use a trolley to avoid unnecessary lifting. Break the load down if possible. If you have to do some lifting, plan it. Clear the working area so you don’t trip. Get help.

Fire

There are several ways in which a fire can start in the workshop. Steel wool very easily ignites from sparks. Oily rags can catch fire spontaneously. Shavings caught up above the bulb of a work lamp can get hot enough to start smouldering, allowing embers to fall into shavings beneath. Cigarettes can fall into shavings. Fire is always dangerous and could destroy the shop, perhaps after you have locked up for the day.

Don’t leave steel wool near sparks from the grinder, or in a drawer with batteries (contact with their terminals will ignite it). Spread out oily rags to dry before disposal. Use cool-running LED lamps, or those with open shades that won’t trap shavings. Keep an extinguisher where you can find it straight away. You know what you should do about smoking – it’s a lot more dangerous than woodturning.

Oh, and don’t superglue yourself to the lathe when there is no-one about to rescue you!

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Wood dust and the hierarchy of control measures

People sometimes misunderstand the facts about wood dust. If you are a woodturner, this is what you should know.

All dust is a hazard

All airborne wood dust is hazardous. That includes hardwood dust, softwood dust and MDF dust. MDF dust is not worse than other kinds. But it easily makes a lot of dust, and more dust can mean more risk. All are capable of causing serious harm such as dermatitis, breathing problems and even cancer. It is not a question of the wood’s toxicity or your individual sensitivity. If some timber species are more dangerous than others, it is hard to say which ones. The proof of harm comes from the mortality of long-term workers in the furniture industry, working with timbers such as beech.
A ‘hazard’ is something with potential to cause harm. That doesn’t necessarily mean that harm will result. That depends on the degree of exposure to it, what precautions you take, and possibly individual susceptibility. The likelihood that harm will actually result is the ‘risk’. As a woodworker, you expose yourself to the dust hazard. To protect yourself, you have to control the risk to the extent you are comfortable with.

Risk depends on exposure

The risk depends on how much dust is present and how long you spend breathing it in. So an occasional turner working green (less dusty) wood is at less risk than the dedicated person who spends long hours hunched over the lathe hand-sanding dry and dusty stuff. Only a small proportion of those exposed to wood dust are likely to get cancer as a result, but turners can easily expose themselves to very high dust levels, well above the legal limit for commercial workshops, at least for short periods. There is no absolutely safe dust level, but if you keep within the legal standards for commercial workplaces the risk is low.
There may be species of wood that you as an individual are allergic to. You may develop dermatitis or breathing problems even after minimal exposure to them. But other species to which you are not now sensitive are hazardous to you as well, just as they are to other people. And you may develop an allergy to another species at any time, even after years of working with it.
Lots of things in the turner’s workshop generate wood dust. Turning, sanding, sawing and sweeping all make clouds of dust. Special lighting reveals it. The fine particles that are most hazardous are almost invisible in the air, and stay airborne for a long time.

Commercial workshops

In a commercial workshop in the UK, the COSHH regulations apply. They require that the risk of wood dust is kept at a level that is unlikely to result in harm. This should preferably be done by using work methods that do not generate dust. Failing that, by removing the dust at source before anyone breaths it in, or by using personal protective equipment such as overalls and breathing masks. In commercial workshops where the law applies, that is the order of choice required. This is a sensible rule in other places too, because masks are never fully effective. It is much better to keep the dust out of the air in the first place.
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Dust control at the lathe. What works best?

Dust control is an important issue for woodturners. We work in an environment where hazardous levels of dust are in the air we breathe. Turning generates dust, and breathing dust is harmful to our health. It can cause breathing problems or cancer. Dust on the skin can lead to dermatitis. All types of wood dust are hazardous, including softwood dust, though some are more likely than others to cause allergy.

The best dust control is not to make dust. Keeping tools sharp, using the less dusty timber species, and wet sanding with water, oil or wax instead of dry sanding, will help reduce dust levels. But most turners make dust and need a way to protect themselves. There are several options for dust control.

Breathing mask

This is the easiest, and at its most basic, the least expensive dust control option. A mask can be effective for low levels of exposure. It may be appropriate for people who do not turn often or for long periods of time, where the cost of dust extraction is not justified. But it is not the best primary protection for most turners. There are several reasons for this.

A mask must seal to the face to prevent unfiltered air flowing under the edge, so a beard is a problem. The filter may impede air flow. The mask may be uncomfortable to wear. Some may cause spectacles to fog. If it doesn’t seal properly, or you take it off when the job is done, you will breathe dusty air. Hazardous dust is so fine that it remains suspended in the air for a long time after work stops. Although a well-fitting mask can protect the wearer, it can only do so while it is being worn.

For many, the best kind of mask is a powered unit that filters the air before blowing it over your face. These can be comfortable, or at least acceptable for hours of use, as the positive fan pressure means that the mask doesn’t have to seal to your face. In addition, the visor and helmet may be impact resistant. If you wear spectacles the air flow will help stop them fogging. But you will still breathe dust when you take the unit off, and a mask will not prevent dust from contacting your skin.

Air cleaners

These filter the workshop air to remove background dust. But they aren’t a complete answer. Most importantly, you work closer to the dust source than the air cleaner does, so the air you breathe carries the heaviest load of dust. A cleaner takes a significant time to remove all the suspended dust in the shop. It’s not just a matter of comparing its rated airflow with the volume of the workspace. The filtered air mixes with the unfiltered, diluting the dust concentration, which goes down slowly as the air passes through the cleaner multiple times. You should put the air cleaner where it will set up a circulation of filtered air around the shop, but there are always likely to be dead spots where dust removal is slower.

Air cleaners are a supplement to dust extraction at source, not primary protection.

Fans

Some people suggest a fan to blow the dust away from the turner. In the right conditions this could work. It will cut the concentration in the inhaled air even if the dust remains in the workshop. If there is enough general ventilation in the shop, the concentration may not build up to harmful levels. But it is not normally a reliable method. The ventilation and the direction of airflow from the fan may vary, and dust may reach harmful levels without you knowing.

Dust extractors

A dust extractor catches the dust at source, before it gets into the general air circulation of the workshop. This is in principle the best solution. It’s the reason workplace health legislation prioritises extraction over the other options.

But not all extractors are suitable. The lathe is a difficult machine to extract dust from. The dust source may be anywhere along the lathe bed or across a spinning disc. The work throws the dust in all directions, including towards you and away from the extraction inlet. Meanwhile, you are bending over the work and breathing in the highest concentration of dust.

The suction has to overcome the speed of the air movement generated by the spinning work. Dust from the tool or from sanding will go with this moving air, which may be quite rapid. You can feel the wind coming off the edge of a spinning disc. This means that a powerful extractor is necessary.

Unfortunately, the suction from any extractor falls off very rapidly with distance from the inlet. At a distance equal to the diameter of the inlet, the air speed is only about 10% of what it is in the mouth of the inlet. This is because the air enters the inlet from all directions, including from behind it. Therefore, to capture the dust effectively the inlet diameter needs to be large, so the dust source can be within its effective zone; it must be adjustable so it can be positioned close to the dust source;  and the extractor must be powerful enough to provide sufficient airflow through the large inlet. Although any extractor is better than none, it’s not enough just to use a large collecting hood if the extractor is too small for it.

It is important that the extractor has a fine filter, or exhausts outdoors. If it doesn’t, much of the dust will return to the workshop. Although a layer of dust inside the filter will itself act as a fine filter, it will also reduce the airflow. With a fine filter, an extractor left running will act as an air cleaner.

Types of extractor

There are two kinds of extractor – high volume, low vacuum; and low volume, high vacuum, which are similar to domestic vacuum cleaners. Lathe dust control needs a high volume air flow to capture the dust, and not high vacuum. There is an overlap between these types of machine, and some powerful high vacuum machines are able to move more air than a small and inefficient low vacuum one.

It is important to check the cubic feet per minute specification. Don’t mistake the high suction that you feel when you put your hand over the inlet for high airflow. The vacuum will pull hard when you block the inlet. But comparatively little air is moving through the pipe when it is open. The amount of airflow needed depends on the turning being done – larger diameter items and higher lathe speeds need more airflow. As a general principle, more is better.

High vacuum machines are very good when the pipe connects directly to the source. But at the lathe, the inlet must move as the source moves, which is not always practicable.

Other dust control issues to take into account are noise levels, ease of emptying, and the quality of the ducting. Ductwork should be as short and straight as possible, as bends and even straight sections increase friction and reduce airflow. Smooth bore ducting causes less friction than corrugated flexible pipe. Leaks at the joints and at blast gates reduce airflow at the inlet. The ducting should be large diameter to reduce friction, but not so large that air moves slowly through it and deposits chips.

Whatever kind of extractor is used, it will often fail to get all the dust. A dust mask can then be used to supplement the extractor.

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Sharpening gouges with a jig

Setting Varigrind cup position

Sharp tools are critical to good work, as all turners know. If the tool is blunt, the wood rejects the cutting edge. If you force it to cut, it tears the grain. But sharpening bowl gouges and spindle gouges can be a challenge. It’s perfectly possible to sharpen them freehand, with or  without the help of a platform set at the correct angle, but this is a skill that takes time to learn. Most people prefer sharpening gouges with a jig. I use a Oneway Varigrind jig, the type to which this article refers.

 There are other jigs on the market, some designed to work with a grinding wheel, which I prefer, and others with a belt sander. There are plans online for making them. They all work in a similar way – they hold the tool to the grinder at a set angle while you shape the edge. Although it makes sure the angle is consistent, the jig doesn’t guarantee the shape of the cutting edge. You control that yourself, by grinding a bit more here or a bit less there.

 Once set up, jigs are quick and easy to use, and can give a consistent and accurate grind, removing the minimum of metal and producing a clean bevel. But how do you set them up?

Templates

The key is to use setting templates. Up to three might be needed for each grind, but they can be made very easily, and some can work with more than one grind. None of the jig settings are critical, as slight variations will make little difference to the sharpened gouge. But the more consistently the jig is set, the less grinding will be needed, so the tools will last longer.

 Duplicating an existing grind

If you have a properly ground gouge to start with, you can usually make templates that will let you reproduce that grind. It will then be easy to reset the jig at any time, so you can either sharpen the original gouge, or duplicate its grind on another one.

I have found that the factory grinds on some new gouges can fall outside the range of the Varigrind. The options then are either to change the grind or to duplicate it freehand, perhaps using a platform set at the appropriate angle.

Usually though, the first step is to set the jig to match the gouge. Use a marker pen to blacken the bevel on the gouge (this is only needed when setting up the first time). Put the gouge in the jig with the correct length projecting, following the jig manufacturer’s recommendation. Two inches is about right. Set the angle of the jig to about the middle of its range, and put the jig in place in the pivot cradle on the extending arm, tilted over as if to grind the wing of the gouge. Adjust the arm until the wheel best contacts the wing bevel, then lock it. This can be seen from the bright streak where the ink is removed when you turn the wheel by hand. It won’t contact perfectly unless the wheel is the same diameter as that originally used.

Put the jig in its central position, so the gouge flute is facing up, and adjust the jig angle until the bevel at the nose of the gouge is in best contact with the wheel, and lock it.

Now go back to the tilted position, and adjust the arm again as necessary.

A couple of repetitions to set the wing, then the nose, then the wing and finally the nose again, will home in on the correct jig settings for that gouge. Remove the gouge from the jig, and make templates (see below) to fit the jig angle and the arm position that you have established. Label them. Then you can quickly go back to these settings at any time.

 Changing the grind

If you want to change the grind of a gouge, you have to adjust the jig and grind the gouge until the required angles and shape are achieved. Then make the setting templates. If you know the angles you want, a machinist’s protractor will help get the settings right. The variables on the gouge are the bevel sharpening angle; the sweep angle of the wings (the angle at which they are ground back from the nose); and the profile of the cutting edge. A fingernail profile with a 55 degree sweep and 50 degree nose bevel angle would be good for a bowl gouge. Other angles can be used according to preference or for particular purposes. It’s a good idea to have bowl gouges with different grinds.

Reshaping

If you are extensively reshaping a gouge, rough out the new grind on an angled platform before starting with the jig. For example, if you want to make a ‘40-40’ grind, start by grinding the 40 degree nose bevel square across without rolling the gouge. Then turn the gouge flute-down on the platform and grind the 40 degree sweep of the wings. The curve of the wheel rim will make the top of the wings concave, so lift the handle slightly when grinding the nose and push forward slightly when grinding the wing ends to make their tops flat. In this somewhat brutal process, you will grind the old cutting edge completely away, but you will clearly see the shape of the finished grind.

The wings

The bevel angle to be ground on the wings is hard to judge without an example to copy. (Perhaps someone can suggest a method?) It’s less than that on the nose, because the inner sides of the flute curve upwards, and the included angle differs at each point along the wing. The included angle should not be too acute as that will make the edge weak and grabby in use. If you don’t have an example to guide you, put the gouge on the 40 degree platform. Swing it to the side and roll it until the wing is parallel to the platform. Then grind a bevel. You will then have a part ground gouge with a correct nose angle. It will have a provisional side bevel that you can use to set the jig as above.

 Sharpening gouges with a jig

When actually sharpening gouges with a jig, or completing a new grind, set the tool in the jig using the templates. Grind the wing on one side, then the other, taking care to keep their tops level and at the required sweep angle.

Don’t let the weight of a long gouge and handle push the jig forward in the cradle. Tools with detachable handles are easier to grind. Roll the jig from just off centre over to one side, without pressure, letting the weight of the gouge do the work. Do the other side, then lightly grind the nose, blending it into the wings to form a smooth curve. Too much pressure, or dwelling too long in one spot, will quickly spoil the shape.

Check the shape

Take care  not to make the nose pointed or square-tipped. Keep it level with the wings, not peaked or dropped.

If reshaping the gouge, the flat top that you made earlier will guide you. But before completing the grind, assess the wing bevel angle. Adjust the jig according to your judgement. The wings should be straight in profile, or slightly convex, not concave.

It can help, particularly when grinding the nose, to switch off the grinder and use its momentum to work as it slows down. This makes the grinder less aggressive. A perfect grind is rarely essential, so if there are minor errors, it’s usually possible to do some turning with the gouge before correcting them during the next sharpening. After a bit of practice the sharpening becomes quick and easy.

 Making the templates

The first is a template to set the jig locking angle. Its design will depend on the grinding jig. Identify two reference points on the jig and make a template to position those points. For the Varigrind, I use two scraps of ply glued together in a wide, flat V. One arm rests against the face from which the gouge protrudes. The other rests against the side of the pivot arm).

Template to set Varigrind jig angle
Template to set Varigrind jig angle

 

 The second is a template to set the gouge projection. At its simplest this can be a stop block the right distance from the edge of the bench. I drilled a blind hole of the right depth in a scrap of wood and fixed it to the bench. A coin in the bottom of the hole stops the gouge nose digging in. I stand the jig on top, face down, and insert the gouge so it is standing free in the hole, then tighten the jig clamp. It’s not normally necessary to change the projection, so this template will serve for most gouges.

Distance template

The third is a template to set the distance of the jig cradle from the wheel. It’s best to reference from the wheel itself, to allow for wear. A dowel of the right length between the cradle and the wheel rim would work, but would not be as positive as a spacer with two-point contact. I use a narrow triangular scrap of board. I cut it too long, then put it in position, but alongside the wheel. The position of the wheel rim can then be marked on it with a pencil and the curve cut with the band saw. Cut enough clearance in the middle so it contacts the wheel at two points.

As an alternative to making a different distance template for each grind, you can use just one distance setting and put spacer blocks of the right thickness in the cradle.

Setting Varigrind cup position
Template to set Varigrind cradle position
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Bowl reversing jaws are easy to make using carrier plates

bowl reversing chuck

Bowl reversing jaws are useful to hold some kinds of bowls by their rims while you finish turning their foot. You can buy sets ready for use, but I made my own. I cut  four plywood squares and then removed a corner from each one with the band saw. I fixed them to steel carrier plates like these that match my chuck. I turned the quadrants true, marked positioning lines, and fixed movable pegs to the quadrants. The pegs form a circle that grips the rim of the bowl. I did the final turning of some of the bowls I sell here using this homemade kit.

First attempt at bowl reversing jaws

The first pegs I tried were pre-drilled rubber bungs from a home-brewing supplier. They have a taper, which gives them a dovetail grip. I drilled holes in concentric circles on the quadrants and fitted 8 mm tee nuts (the kind with prongs to hammer or press into the wood). 8 mm bolts held the bungs firmly in place. There was a neat ring of 8 bungs on the bowl reversing jaws ready to grip almost any size of bowl.

I expected the soft rubber to have a non-marking grip and accommodate small positioning errors. But the rubber bungs turned out to be a bad idea because they had too much ‘give’. I found that any but the lightest cuts could move the bowl in the chuck. My next move was to turn a set of wooden pegs to replace the bungs. Another option would be to make solid wooden jaws, fixed to the quadrants and turned to give a more even grip on the bowl. These would have to be renewed from time to time.

Making the wooden pegs

This was an easy job. I cut short sections of a moderately soft timber (from an old curtain pole) and drilled an 8 mm hole right through the middle of each one. I mounted them in the lathe between a conical ‘dead’ centre in the headstock and a live centre in the tailstock. The dead centre had enough friction to drive the piece. Doing it this way ensured that the holes were central in the finished pegs.

I turned the pegs to the same size as the rubber bungs. They are 30 mm long, 30 mm wide at the top and 26 mm wide at the bottom. I could have used shorter pegs, but I had Allen bolts the right length for that size. I used a parting tool and calipers to set the greatest and least diameters. A sharp spindle roughing gouge cut the slight taper. I used a skew chisel to square the ends so they would sit firmly on the quadrants. After using them, I found that changing the position of the pegs is more convenient if they are a tight fit on the bolts, so I added a little glue to the thread. This allows the pegs to be tightened in place on the quadrant without using a key.

It’s important to position the tee nuts accurately so the pegs grip evenly.

Testing the new pegs

I used them to remove a temporary chucking tenon from the base of a Robinia bowl. They held better than the rubber bungs. But hard wooden bowl reversing jaws of this type cannot be tightened too firmly or they will damage the bowl’s rim. They never give the most reliable grip and heavy cuts cannot be taken.  Also you need to decide a safe maximum speed on the lathe. Tailstock support will give more security. Even so, wooden pegs could mark or damage a fragile rim, so care is needed. I have heard of people using a rubber sleeve over a wooden core. Rubber tubing or even plastic hose pipe might work for this.

Bowl reversing jaws
Wooden pegs to grip bowl

 

Since writing this post I have bought a commercially produced jaw set from Axminster Power Tools. It has aluminium carrier plates and white rubber pegs, smaller than the ones I made. I have to admit that they work better than my homemade version, with a more secure grip and no damage to the bowl.

If you make a set, aim for stiffness in the quadrants, secure fixing of the quadrants to the carrier plates, accuracy in the hole positions and use smaller pegs than I did. The white rubber works well. Run the lathed at a speed you are comfortable with.

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Gouge vibration – causes and prevention

Gouge vibration is a problem that besets people when they are learning to turn bowls.  The gouge bounces on the wood, and no amount of pressure seems to stop it, however strongly they grip the tool. The more they continue, the worse the vibration gets. Unsightly ridges appear on the turned surface. It usually affects the outside of the bowl. This gouge vibration has two causes.

Irregular bowl blanks

This is the most obvious cause of gouge vibration. When roughing out an uneven blank, it is very easy to push the gouge forward into a low spot. When the high spot comes round, it hits the tool bevel and knocks it back. This immediately sets up an in-out rattling vibration. To overcome it:

  • Increase the speed of the lathe (as consistent with safety, and not so fast that the machine shakes or there is any risk of a chunk flying off, which would be highly dangerous). There will be less time in each revolution for the gouge to move forward.
  • Lower the gouge handle or twist the gouge so the cutting edge is more square to the wood. This lets the wood be sliced off before it gets to the bevel. But caution is needed. It could be risky if the tool pushes too far into the gap and the cut is too heavy. Keep the tool rest close.
  • Take care not to push the gouge against the wood. If pressure seems necessary to stabilise the tool, apply it downwards against the tool rest.
  • Reduce the feed rate – allow the high spots time to come to the tool and be sliced off.
  • Adjust the tool rest closer and use a bigger gouge. Small gouges can flex and set up vibration. If the gouge reaches too far over the tool rest, it magnifies the effect of incorrect technique. The gouge is harder to control.
  • Make sure the gouge is sharp. Blunt tools make for hard work.
  • Cut the bowl blank closer to the finished shape before putting it on the lathe.

Pressing the bevel on the wood

More baffling is when gouge vibration begins for no obvious reason part way through a cut that has been going smoothly. As the cut continues, the vibration rapidly gets worse. The cut becomes noisy, and when you examine the surface, there are spiral ridges.

The cause is pressure of the tool bevel on the wood. Any attempt to control the gouge vibration by pressing harder will fail. It is often said that the bevel should rub the wood, but this is not strictly true. The bevel should be aligned with and in contact with the cut surface, but should not press against it with any significant force. Pressure compresses the softer parts and when a harder area comes round it throws the gouge out. The vibration is slight at first, but each time the hard parts come round the effect grows. The softer parts are cut deeper and the ridges get bigger and bigger.

  • When gouge vibration begins, stop or adjust the cut immediately.
  • Make sure the gouge is sharp, and move the tool rest closer if necessary.
  • Move the tool back to a point where there is no vibration and the bevel can rest quietly on the surface. Align the bevel in the direction of the cut, then lift the heel of the bevel very slightly so that the wood contacts the cutting edge before the bevel.
  • Make sure there is no pressure on the wood, but stabilise the gouge by pressing down against the tool rest and holding the tool handle to your body. Don’t extend it too far over the rest. Restart the cut, moving the gouge forward slowly enough  to remove the ridges as they come to the tool.
  • Sometimes taking a heavier, more positive cut will help eliminate the problem.

 

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Torn grain and tear-out. How to deal with and prevent torn grain

Some people spend hours sanding a bowl to get a reasonable finish. But, apart from the tedium, not to mention the cost of sandpaper, excessive sanding can have a bad affect on the finished bowl. It is not the best way to deal with torn grain. Heavy sanding should rarely be necessary, and there are a number of things to try before getting out the 40 grit. I thought it might be worth setting down some of the things that help to prevent torn grain when turning bowls.

To achieve a good surface without torn grain, you have to cut the shaving in a way that allows it to separate cleanly without damaging the underlying material. As the gouge pushes between the shaving and the wood beneath, it acts as a wedge.  The shaving has to bend to slide up and over the wedge. If the shaving is stiff, it will not bend easily, and because its fibres extend back into the main body of the timber, the stress can start a split that runs ahead of the cut. 

On the end grain areas, the wedging action pulls on the fibres and if they are weak they can break below the surface and pull out. The fibres are not cut, but torn apart. Tearing usually occurs either where the surface is changing from end grain to side grain as the wood rotates, or where locally disturbed grain opposes the cut. These are situations where such a split can easily start and propagate.

To prevent torn grain during final cuts, you need a thin, weak shaving that cannot transfer much force back into the uncut fibres. It must only bend through a small angle, and the uncut fibres must adhere to each other strongly enough to resist being split apart.

How to get a good surface

  • The first thing to do is of course to sharpen the gouge. The edge is then better able to cut the fibres before any gap opens in front of the cutting edge.
  • Increase the lathe speed (as consistent with safety. A chunk separating from a fast-spinning bowl blank is dangerous). For a given feed rate, the shaving will then be thinner and less robust. This allows it to separate from the timber with less stress on the remaining wood.
  • A slower feed rate will also remove less wood per revolution, making thinner, weaker shavings. They can bend and break easily without much leverage on the fibres not yet cut. Many beginners rush to complete cuts before something goes wrong. Let finishing cuts be slow and gentle.
  • A lighter cut, like a slower feed rate, will make the shavings thinner so they pull less. For best results, make the final cuts as light as possible. A very sharp gouge makes this easier.
  • Use a smaller gouge. The tighter radius at the point of cut will take a narrower shaving, which again will be weaker and will separate more cleanly. This is why the curved edge of a gouge will sometimes cause less torn grain than a skew chisel when spindle turning.
  • Make sure the bevel aligns with the surface underneath, without pressing on the wood. If the heel of the bevel lifts from the surface, it changes the top angle and the shaving has to bend more to get into the gouge flute. The tool is harder to control too, and tends to make grooves in the surface.
  • On the inside of the bowl, a short bevel will fit the curved surface better than a long one. It reduces the top angle and improves support and guidance of the tool.
  • A keener, more acute sharpening angle on the gouge will also affect the top angle. Any sharp edge will cut, but a smaller bending angle for the shaving will usually reduce the pull on the fibres. However, an acute sharpening angle can increase the wedging effect, resulting in a worse finish on some woods.
  • Present the cutting edge at a skewed angle. The effective top angle and bevel angle are at a maximum when they meet the oncoming wood square on. If you skew the edge, the wood sees the angles as smaller and more acute and the shaving slips over the edge more easily. Also, the skewed edge takes a narrower shaving. A traditionally ground bowl gouge (ground square, or nearly square, across) can be used with the wing at a very skewed angle, giving a very clean cut.
  • If necessary, make the final cuts with a very gentle scraping action. The lower wing of a swept-back gouge, with the flute closed and the handle down to skew the edge, will take extremely fine, fluffy shavings. It removes very little wood on each pass. You can also use a diamond point flat scraper, on its side to skew the edge. It is easier to keep sharp than a gouge, and can be given a rolled burr using a burnishing rod. Shear scraping like this will usually get rid of ‘macro’ torn grain but does not leave a burnished surface as a bevel-guided cut can.
  • Use a negative rake scraper flat on the rest. Beginners sometimes unintentionally lift one side of the tool off the rest, which causes minor dig-ins that tear the grain. The shaving has to bend sharply as you cut it, but the top angle is too great to create a wedging action. Provided the shaving is thin and there is no vibration, a reasonable or good surface may be achieved. Too much tool projection can cause vibration, and so can thin walls on the bowl. Most woods respond best to a correctly used gouge.
  • Cut the wood ‘with the grain’. Turn the outside of a bowl from bottom to top. Turn the inside from the rim to the bottom. Then the fibres approaching the tool are short and running out of the surface of the wood. Any split that begins to form will follow them and exit the surface before doing damage. In addition, the fibres are supported by those below. Then the gouge can cut them rather than break them off.
  • Wet problem areas with finishing oil or water. It lubricates the cut and softens the fibres to allow the shaving to bend easily. Wood with high moisture content usually cuts better.
  • Some timber species  are more prone to torn grain than others. Their fibres separate more easily. It is possible to apply shellac or other sealer to reinforce the uncut fibres. This makes them more resistant to splitting apart. 

Sanding

If your best efforts still leave noticeable torn grain, you will need to sand to remove the damage. There will almost always be some sanding needed to remove tool marks too. 120 grit counts as coarse. I usually start with 120 or 180, and the sanding takes only minutes. If you sand just the defect you end up with a depression, so you have to sand away the surrounding high areas too. Sometimes you can get away with spot sanding with the lathe stationary, then blending it in with the lathe running.