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Homemade calipers are helpful when turning bowls

homemade calipers

Getting the wall of a bowl the right thickness is very important. The wall doesn’t have to be the same thickness all the way down, but it must look and feel right. An experienced turner would likely rely entirely on their sense of touch and not use calipers at all. But simple, non-adjustable homemade calipers can help. They are quick to make and use. Calipers are normally adjustable, and made of steel. But adjustability is only necessary if you actually need to measure the thickness. I find that when using ordinary steel calipers to check the wall of a bowl, I set them to more than the thickness anyway. By watching the gap between the point and the wall, I can see that the thickness is right. I made a batch of fixed ones to help with the teaching I do.

Material for homemade calipers

I used scraps of 6 mm MDF. This is unlikely to scratch the finished surface of a bowl, which plywood might. But with care in use, other materials would be fine. Dimensions are not at all critical, as long as the central cut-out is big enough for the caliper arms to reach down to the bottom of the bowl. They could be made in any size.

Making the calipers

I cut the blank to a circle with a band saw and drilled a small hole in the middle for the revolving centre. I then pinned the disc to the jaws of a chuck with the tailstock. This is a very quick method of mounting discs in the lathe. Friction from the chuck jaws drives them. I trued up the edge of the disc. Turning MDF is dusty, but very easy with a scraper. Then I marked an off-centre circle and cut the middle out with the band saw. The entry cut is at the narrowest point. I sanded the inner curve with a drum sander, but this, like the turning, is purely for appearance. Hand sanding, or no sanding, would work just as well.

Then I enlarged the entry cut and sanded the ends of the arms. Although these calipers have no adjustment, it would be easy enough to cut them in half and drill for a bolt and wing nut. The gap should be a little more than the likely wall thickness, say 15 mm for walls of 12 mm. When one arm slides down the inside wall, the gap between the other arm and the outside of the bowl clearly shows changes in thickness. I drilled a small hole for hanging the caliper on a nail.

 

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Homemade faceplate rings

Faceplate rings are useful in bowl making, and also as a quick method of mounting things such as sanding discs in the lathe. They allow you to work on a batch of items over a period without having to remove the fixing. I needed a number of them, and now have a batch of homemade faceplate rings. They are a good alternative to a screwchuck

Making the rings

Instead of the usual steel or light alloy, I made my homemade faceplate rings from good quality birch plywood, free of voids. They are about 100 mm across and 12 mm thick, but other sizes would work. After bandsawing the blanks, I marked the centres and pinned each one against the open jaws of a chuck with the tail centre. This is a quick and easy method of driving small items by friction. I turned the rims true, then gripped the discs by their rims in the chuck. For this I used an engineering chuck, but could have made a jam chuck from scrap wood. I used a small skew chisel to bore a tapered hole right through each one.

Just as when making a chucking recess in a bowl, the holes need to fit the jaws of the chuck that will hold the rings. The diameter should fit the jaws when they are almost closed. The taper should match that of the jaws reasonably closely.

I then mounted each ring in the chuck it was intended for and marked a circle on it. My lathe has an indexing ring, so I used that to divide the circle into thirds for the screw holes. Without that, I could have used a strut under the chuck jaws to locate the holes for the screws. I drilled the holes to suit the fixing screws. They have a countersink on one side for the screw head, and on the other to accommodate swelling in the timber made by the screws when in use.

Durability of homemade faceplate rings

I was slightly concerned that the expanding chuck jaws could cause the ply to de-laminate in use. However, the screws prevent the layers from separating. I put the screw holes fairly close to the recess, where the stress would be greatest. Wooden rings cannot be as strong as steel, but these are holding up well. They should be at least as strong as the chuck recess made in a wooden bowl.

With an offcut of plywood and a little time, I have a number of very useful homemade faceplate rings, saving the significant cost of factory-made ones.

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Homemade tools for woodturning

Woodturners need cutting tools.  In past times, they made their own tools, or went to the local blacksmith. Most people now buy their kit ready-made. But homemade tools are still useful. Some turners still make their own tools. They do it to save money, or because they need a special purpose tool that cannot be bought. Some do it because they enjoy the tool making as much as they do the turning.
I enjoy toolmaking, though I have to admit I don’t pay enough attention to the look of the finished results. I hesitated before posting photos on this page. None of my homemade tools will win a prize in a beauty contest. But they all work, and among the tools I use quite often, about half are either homemade or modified in some way.
Homemade tools for woodturning fall into three main groups:
  1. gouges
  2. scrapers and chisels (flat tools)
  3. tipped tools

Homemade Tools – equipment and materials

Making tools needs some basic metal working equipment, such as a file, a hacksaw, a few threading taps, a grinder and a bench drill. Simple forging needs a makeshift anvil, vice, pliers and a hammer, and a source of heat such as a charcoal fire or a blowtorch. See my post on hardening and tempering steel for details.
Gouges and flat tools can be made from high carbon steel. This is now rarely used for commercial turning tools, apart from cheap starter sets. High speed steel has almost completely replaced carbon steel.
High carbon steel was known as tool steel, and once was the only choice for making tools. Carbon steel tools can take a very good cutting edge. They can do just about anything that modern high speed steel tools can do. But they are less resistant to abrasive wood, so need frequent sharpening. And they lose their temper easily with heat. So they need more care when grinding, and lathe speeds must be lower.
Tipped tools are usually scrapers, the tips being HSS or tungsten carbide.
Carbon steel, though rarely used for woodturning tools, is still widely used for other purposes. You can buy it, for example as silver steel, or find it as scrap. You can make cutting tools from old files, springs, motor parts and all sorts of other scrap. I have used the tines of a garden fork, the rings of ball races and screwdrivers and chisels.
Files are carbon steel. It was once common practice to make them into very effective scrapers and chisels, but there is a potential problem. The grooves between the teeth of the file can start cracks in the steel. Though I have not known it to happen myself, this could lead to the blade breaking under stress, which would be dangerous. If you choose to make scrapers from files, you should use only thick, heavy, fine-toothed ones. Grind away all the teeth and grooves and check carefully for any visible cracks. Then thoroughly anneal the tool, re-hardening and tempering just the tip.
A scraper made like this is unlikely to break in normal use. But you should not put it under severe stress, for example from heavy, intermittent cutting on an uneven blank. A bad dig-in could also break a weak tool. This problem can also affect corroded steel. So it is safer to buy commercial scrapers for woodturning, or use only sound, bright and thick steel if you want to make tools for heavy work (or think they might get used in this way at some future date).
You can use HSS tool bits to make gouges and all sorts of scraping tools. You just secure them in a holder that is usually made of mild steel or unhardened carbon steel. Some tool bits are long enough to fit into a wooden handle directly.
Tungsten carbide tips are becoming more widely used in woodturning. Not all grades of carbide are suitable however. Most tips available are for metal turning and cannot be made sharp enough for woodturning. But you can use tips of the proper grade of carbide to make scrapers that perform very well.
Homemade gouge converted to beading tool
A homemade gouge ground as a beading tool

Gouges

These at first sight may seem difficult to make. But there are several ways to make the flute of a gouge:
  • Forge the flute. It needs some skill to get an even flute, and more equipment, such as swages to form the shape. Good fun to do if you have the facilities.
  • Grind the flute. Make a small gouge by grinding or filing a flat on a carbon steel rod (such as a heavy screwdriver), then using the edge of a small grinding disc to form a groove. The flute does not have to be full length – 15-20 mm long will function perfectly well. You can use this method with high speed steel or hardened carbon steel.
  • Drill the flute. Use a twist bit to drill into the end of a carbon steel rod, making a hole at least 20 mm deep. Then just file or grind away half the hole, leaving a groove. This is the easiest method and gives a uniform semi-circular flute. The internal surface will benefit from light grinding or polishing to reduce the minor scratches left by the drill. Even better is to drill very slightly under size then use a reamer to clean up the hole. You must anneal the rod before drilling, grind the bevel, then harden and temper it later. I’ve made several of these drilled gouges in various sizes, and use them often. They are all small, but the method would work for larger gouges too. Ready-made small spindle gouges are often too thin and flexible for safe use.
small homemade spindle gouge
Small homemade spindle gouge with drilled flute of about 2.5 mm

 

small homemade detail gouge
Small homemade spindle detail gouge

 Scrapers

These are very simple to make. All sorts of scrap are suitable. You just have to grind a carbon steel bar to shape, harden and temper it correctly, and fit it with a handle. A long and thick HSS tool bit will fit directly into a wooden handle and make an excellent scraper. You can make chisels in the same way.
homemade square chisel
Homemade 45 mm square chisel made from a vehicle leaf spring
hollowing tool made from garden fork tine
Homemade hollowing tool made from fork tine
This tool was hot forged, in the same way that I made this hook wrench. I hardened and tempered its tip.

Homemade tools with HSS or carbide tips

These tools are also very easy to make. You just have to adapt a steel bar of suitable size to take the cutting bit, either of high speed steel or tungsten carbide. It’s easy to hot forge the bar into a curve to make hollowing tools.
You can buy square or round HSS  tool bits from Ebay. All that is necessary is to drill a hole in the end of the steel bar with one or more tapped cross holes for grub screws that will hold the HSS securely in place. More simply, you can just glue the bit into the hole. Heat will release it later if necessary.
You can silver-solder or braze flat section HSS tool bits to the top of the bar, with or without making a step for them. I used this method to make a ‘fluteless gouge’.
Tungsten carbide cutting bits usually go on top of the steel bar, with a single locking screw through the bit into a tapped hole in the bar.
I made the lower of the two scrapers shown below from a solid carbide burr and shaped it with a diamond burr in a Dremel tool.
Homemade carbide tipped scrapers
Carbide tipped scrapers

Graver

This is a tool like a woodturners’ point tool, with three flats ground on a round bar, in this case of high speed steel. You use a graver for turning mild steel freehand. See my post on turning metal in a wood lathe for details. Gravers work on wood too. You can make a graver from square bar by grinding a single diamond-shaped flat from one corner to the one diagonally opposite, at an angle. This gives two cutting edges.
homemade graver for metal turning
Homemade graver made from round HSS

Safety

Please pay attention to safety when using homemade tools. There can be risks if you exceed their safe limits. Don’t use homemade tools if you are an inexperienced turner because you may not recognise these limits. If you can’t rely on your own judgement, don’t try it!
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Tormek review – Is this the best machine for sharpening woodturning tools?

The Tormek is one of the best machines available for sharpening woodturning tools. It has a slow-running wet grinding wheel and a honing/stropping wheel. It comes with many optional accessories. I have the ‘Supergrind  2000’ model. For a long time I used the machine for sharpening my spindle gouges.

I don’t recommend the special woodturning kit if you also have a high speed grinder. It includes things that you will probably use only rarely, if at all.  The things I use are the adjustable gouge jig shown below, and sometimes the small stropping wheel for gouge flutes. I use the large stropping wheel for bevels.

Tormek review

The Tormek is robust, quiet and generally well-made. It does a great job, giving an edge straight off the grinding wheel that is a pleasure to use. The grind is accurate and consistent. If heavy grinding is not needed and you keep the jigs set up for a single bevel angle and shape, the Tormek is quick and easy to use. It will also sharpen bowl gouges very well. So far, so good.

I find that I often have to take more metal off a bowl gouge to restore the edge than I do with a spindle gouge. That’s because the greater diameter and larger amount of waste to remove means the tool has more work to do. Also, the bowl gouge is often used with a scraping or semi-scraping action. Bowl blanks are usually log sections with bark, and usually have grit in or on them. In addition, we tend to tolerate blunt gouges until the final cuts on a bowl. Having to grind for longer makes the Tormek slower than a high-speed dry grinder set up with a bowl gouge jig. I have such a grinder and find that I prefer that for my bowl gouges. Similarly with scrapers, which are sharpened very often. A dry grinder is fine for those.

Minor problems

The Tormek is expensive for what is really a very simple machine. Its performance is in some ways disappointing, with a number of minor problems:

  • the drive slips. When the machine has been used for a while, pressure on the grinding wheel begins to make it slow down and stop. This gradually gets worse until it becomes a problem. It is easily remedied by cleaning with abrasive the rubber friction wheel on which the motor spindle bears. Then it starts gradually getting worse again. The friction drive is an extremely simple way to get the very low speed. But I can’t help thinking that there should be a better arrangement with a more positive drive.

The stone wheel

  • The stone wheel is soft, wears rapidly, and is strangely expensive to replace. Harder wheels are available, including diamond faced ones, at an even higher price. If you use a Tormek for gouges, especially bowl gouges, you have to keep them moving across the grinding surface to spread the wear. Even so, the wheel will soon develop grooves, and is then harder to use for flat tools such as chisels. You can still sharpen them by sliding the tool sideways so the high spots of the wheel do all the work. Indeed, this will tend to correct the uneven wear. If the tool remains still, its edge will be ground unevenly and will not be straight. You can buy a diamond tipped tool for truing the surface. The old model truing tool I have is not easy to use, because the slow speed of the wheel makes the diamond cut a spiral. And of course, each time you use it the wheel gets smaller. I sometimes use one of the diamond matrix dressers sold for high-speed dry grinders, using it freehand. Its wide contact area prevents the spiral grooves forming. The Tormek ‘stone grader’ block is used to dress the wheel, but soon wears hollow and begins to lose its accuracy. I have not found the stone grader useful.

Gouge jig

  • To set the gouge jig to the angle required needs an Allen key. A thumb screw or wing nut would be more convenient. But if you normally leave it at the same setting, the key is not a problem.
  • The swiveling gouge jig has plastic bushes that slide on the tool rest bar. They are not secure in the jig, and can fall out and get lost, though in fairness I should say that this has only happened once (so far).
  • This jig clamps over the gouge flute. It has a brass disc that bridges the side wings and a small brass peg that goes into the flute. When the flute gets shorter, the peg starts to contact the flute bottom where it curves up at the handle end, and the jig loses its grip on the gouge. This can affect the grinding angle because it allows the gouge to slip backwards if you don’t notice it is loose. You can  grind a flat on the tool for the jig to clamp on, and extend and deepen the flute, letting you carry on grinding short tools, but the grip is not as secure and the self-alignment is lost.
  • The motor is not reversible. Making it so would remove the need for two tool rest bars. And the motor is single speed. Variable speed would make the machine more versatile. These are common features in many electric tools now.
  • The water trough is a little awkward to take on and off, and easy to spill, so you may need to stand the machine in a tray.

Bearings

Stropping

After grinding, you can strop the tool on the leather wheel. But you first have to re-set the jig. This is because the two wheels are not the same size. The obvious answer, making the honing wheel bigger, would not solve this problem as the grinding wheel soon wears down. If you grind with the wheel running towards the tool edge, you will have to turn the machine round and move the tool bar to use the honing wheel. And only one tool bar is supplied as standard. Usually I skip the power stropping, though sometimes I use a hand-held leather strop. With care, you can strop tools on the Tormek freehand, and it gives a really sharp edge. But it is easy to dub the edge over. The edge straight from the grinding wheel is very good for turning tools.

Wet grinding

One of the main selling points of the Tormek is the water bath for the grinding wheel. I find that the water evaporates quickly. Rather than have the wheel clog up with salts from our hard tap water, I use rainwater from a butt next to the workshop. Carbon steel is easily overheated on a high-speed dry grinder if you are heavy-handed. It turns blue at the edge and loses its temper. The tool is not ruined, but that part of the edge will not stay sharp very long. The Tormek will not blue the edge, because of the water flowing over the tool, and because the stone turns slowly. But with care, a high-speed dry grinder will not blue the steel either. You just have to keep the wheel clean, keep the tool moving, and avoid pressure and dwelling on one spot too long.

When I started turning, many years ago now, carbon steel tools were the norm, and modern grinding jigs were not available. I learned to grind them freehand on a high-speed grinder with long-lasting hard grey wheels. Almost all turning tools now sold are high-speed steel. This is very resistant to heat, and will not lose its temper in grinding.

So it seems to me that the principle feature of the Tormek is not really essential, for turning tools at least. The water doesn’t do any harm, and it does carry away the grinding dust. Without water, the dust would cling to the cutting edge, because steel tools often become magnetised. The water keeps the grinding wheel clean too. Using water could be a problem if it freezes.

Jigs

I normally use only the gouge jig, keeping it set for my spindle gouges. It is easy to make setting blocks for it, with different angles to suit different gouges. Then you just have to slacken the screw, lay the jig on the block, and re-tighten. I also use this jig and the platform jig on my high speed grinder which I have set up with a Tormek tool rest bar.

You can also make a stop block to get the gouge projection the same each time, one to set the tool rest bar position, and another to set the position of the height adjustment clamp (though I never change this). These setting jigs (or simply not changing the settings at all) are the key to getting a quick result from any grinder. The one below for setting the gouge jig has two different angles, one side for bowl gouges and the other for spindle gouges.

Tormek setting block
Tormek setting block

Sharpening woodturning tools

The Tormek puts an extremely good edge on turning tools, and being slow running, it is easy to use for a beginner – you’re less likely to accidentally grind away too much metal in the wrong spot, though even with the jigs it is still possible to end up with the wrong shape. With setting blocks, it is quick to set up, and quick to use for sharpening. It will not burn the tool edges. Tools become really sharp, a pleasure to use.

However, it is very expensive. Grinding is painfully slow if re-shaping a tool. You have to maintain the wheel and the drive. And you have to top up the water bath often, and clean it.

Dry grinding

It is perfectly possible to sharpen turning tools, including spindle gouges, with just an ordinary high-speed dry grinder. You can do it freehand or with simple jigs that can be homemade if necessary. The tools will not have as good an edge as the Tormek gives. But they will be sharp enough for good work.

Both machines are useful and I like having both. But if I had to choose between my Tormek and my high speed grinder, I would keep the latter. If you want to do more than just sharpening, the high speed machine is more versatile. And you can always use a diamond stone to hone the edges after grinding. And you can strop them with polishing compound on a bit of leather glued to a strip of wood. This can give an edge as good as the Tormek. Here is a post on using Tormek jigs with a high speed grinder

There – perhaps this Tormek review has just saved you some money!

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Homemade compasses, any size you like

Here is a useful tool for turners – a giant pair of homemade compasses. When preparing large bowl blanks the usual commercial compasses may be too small. I made a large pair from scrap wood. Opened to 90 degrees, they can make a circle of 800 mm radius. You could make them any size you like.
My pair has arms about 550 mm long, made of planed scrap softwood. They are joined at the top by a small coach bolt, washer and wingnut. One arm has a pointed nail inserted, the other has a simple clamp to hold a pencil. Drill the hole for the coach bolt the same diameter as the bolt. The square part of the shank will pull into the hole when you tighten the wingnut, and stop the bolt turning.

The point

To insert the nail, drill a small hole in the end of the arm. The hole should be just a little less in diameter than the nail, to make it secure without splitting the wood. Cut off the head of the nail and grip it point down in a vise, then tap the arm down onto the blunt end. Cut the arm to a blunt point so the corners don’t get in the way.

The pencil clamp

To make the pencil clamp, drill a hole for the pencil first, making it a sliding fit. I shaped the end of the pencil arm a bit, but that isn’t essential. I just thought it would look better that way. But a blind hole for the pencil might make it less convenient to adjust. Then drill a cross hole, close to the pencil hole but not intersecting it. Now make a saw cut to split the pencil hole down its middle. Go a bit past the cross hole so there is some spring in the wood. Fit a small coach bolt, washer and wingnut in the cross hole. When tightened, it will close the saw cut and pinch the pencil to stop it moving.
Smooth off any rough edges, drill a hole through both arms near the pivot so you can hang it up, sharpen the pencil, and your homemade compasses are finished.
pair of large homemade compasses
Large pair of homemade compasses

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Tips for copy turning


Inexperienced turners find copy turning quite intimidating. But making two or more pieces the same need not be difficult. After all, when you have turned the first you have proved your ability.

Copy turning attachment

A copy turning attachment for your lathe is one option. But it’s only really worthwhile if you have a great many items to do. The attachment must be paid for, set up and taken down, and may get in the way when not in use. It may not even save time. For most turners it is better to save money and benefit from the practice that hand turning will give you. Soon you will be able to make duplicates so quickly that you will surprise yourself. Making lots of the same item is an excellent way of building your skills. You will find you can then make other shapes much more confidently and fluently. And why take up woodturning if you don’t want to do the turning?
When you make a set of turnings, they need to be very similar both to each other and to the original pattern. But it is rarely necessary for copied items to be indistinguishable. Slight variation is almost always acceptable, even desirable. It shows that the items are handmade. If you look at antique furniture you may well see minor variation in the spindles. It’s part of the charm of the piece. Of course, this is not an excuse for sloppiness. Generally, the closer together you place two items, the more closely they should resemble each other. At the other extreme, if the items are to be sold separately, a family resemblance may be enough.

Critical dimensions

The most important dimensions of a spindle being copied are usually the overall length, the maximum and minimum diameters, the diameter of any tenon or fitting, and the position of beads or other prominent features. The exact size or shape of beads, fillets and coves is not normally so critical. If one finished item does not stand out markedly from the others, the set is probably OK. But the tighter the specification, the more care has to be taken with measurements, marking out and the turning.

Tips for copy turning

It’s probably not worth attempting copy turning (unless you are doing it just for the practice) until you are able to produce beads and coves with reasonable reliability. Assuming you can do this, first make one complete item to your satisfaction. This proves that you can do the job, and is a sample that acts as a guide for the rest. Make a holder for it that positions it just behind the lathe so you can see it when working on the others.
When doing the rest of the items, it helps if you break the task down into steps and put all the items through each stage before going on to the next. The advantages of this are first that the practice gained from carrying out that step on the first item is immediately put to use on the next. Secondly, you can see as you go that each one is within tolerance. You should start with some spares to allow for any rejects along the way.
This is not the most efficient method of production, as you must spend time changing over the blanks. So with more experience you will probably complete each item before going on to the next. However, by working in small steps the turning is simpler, mistakes may be less likely, and you will soon become quick and confident at each stage.
You may have a motley collection of scrap wood to work with. If so, it makes the copying easier if you start by making the blanks identical. You will then have a stack of cylinders all the same size. Make them just slightly more than the maximum diameter of the finished piece to allow for sanding.

Marking out

Make a template by marking the key points from your sample onto a piece of thin ply. You can offer this up to the spinning blanks and mark circles on them with a pencil. The number of points and circles will depend on how accurate you want the copies to be. Usually, I mark the centre line of each bead, the position of any tenon and the overall length of the item. I don’t normally mark or measure the width of beads or hollows or fillets. This is partly because if there are too many lines drawn on the blank it is confusing and leads to errors.
If this is a job you will repeat in future, label the template, sketch the item on it with the marks for the key points in the right places, write the relevant finished diameters and size of the blank and put it somewhere safe.

 Prepare the tools

Sharpen and lay out the tools for the job. If possible, have enough pairs of calipers to make all measurements that you need – not usually more than three or four. Set them to slightly over the relevant finished diameters to allow for small errors and sanding. In softer wood the calipers can damage the surface, so if possible don’t use them right on the crown of  a bead. Calipers without lock nuts can open slowly in use, a source of error. Lay them out in order so you don’t mix them up. You might label the calipers to correspond to the positions on the marking strip. With practice, you may find that you only need to use one or two pairs. You can judge other diameters by eye, using the measured diameters or sometimes the drive centre or tail centre as points of reference.
Use a parting tool to set the bead diameters with the calipers. When you have set the diameters, if the shape permits it, part in on each side to block out the beads, centred on the marked lines. With practice you will have the confidence to set the width and depth by eye. The parting cuts both locate the beads and make clearance for the gouge or skew. Sometimes there is no room for the parting cut, for example if there are two beads side by side. Then you will have to make V cuts instead with the skew or spindle gouge.

Turn the shape

When copy turning, turn the beads first, then the coves, then clean up the fillets. Measure if you need to, or if the size is critical, but try to set the width of any fillets and the depth of coves by eye. Aim to get all fillets on an item of equal width, and all coves and beads properly shaped. If you shape them properly, the finished dimensions should come out right each time. Pay particular attention to the shape of larger coves and beads and sweeping curves. Size the tenons, if any. Many turners use a spanner to get the diameter right, cutting with a parting tool.

When you have finished the batch, line them up and pick out any rejects. If you need small sets, sort them into groups that match best. Here are a few spindles I made using these methods. After sawing the blanks to size and turning the first three, the only measurements necessary were to mark the positions of the beads using a marking strip and to size the tenons.

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New website

Until recently I operated a website at www.turnedwoodenbowls.com. Because of technical problems with it, I set up my new website here. I think it already looks and works better for visitors than my old one, which I have now closed. It’s easier to manage too, though I still have a lot of work to do on it. I haven’t yet republished all of my old posts, and I still have to transfer some images.

I have migrated my list of subscribers. So if you are one of them, you will be notified when I add new posts, and I thank you for your interest.

I’ve published a couple of new posts here so far, on sharpening and on dust extraction. More will follow, so if you haven’t yet subscribed, please do.

Most of the wooden bowls and other things on my product pages here are new. In due course I shall list stock from my old site here. If you are looking for a specific item, just let me know.

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Tapping a thread in steel is a useful workshop skill

This post is for people with little experience of working in metal. Tapping a thread is a useful workshop skill. It’s easy to cut threads in steel with a tap. You can use a drill and tap to fit a cutting bit to a tool shaft, assemble steel parts, or to make up frames for tool stands etc.

Drill the hole

Drill the hole for the thread using a tapping drill. This is just a normal twist bit the correct size for the particular thread. When drilling holes in steel, you need a bench drill with the speed set slow. This makes a hole that is square to the surface of the metal. When drilling metal like this it is essential to use a vice or clamp. The drill can catch when it cuts through, spinning the metal round and doing your hand no good at all.

The size tolerance is small, and accuracy is important. If the hole is bigger than recommended, the thread will be weaker, though the tapping will be easier. If it is too small, you will find the tap makes the hole bigger without getting a grip in the metal and cutting a thread.

The correct size of hole depends on factors including thread form and thread size. There are a lot of thread forms, such as Whitworth, BSF and BA, for which drill size tables are available online. I include here tables for the smaller metric threads and Whitworth threads that are commonly used in older machinery.

Taps

Taps come in all sizes and threads. You can identify the right tap to match an existing male thread such as a bolt by placing them side by side with the thread peaks lined up. Hold them up to the light, and you can see any mismatch further along the tap. If the diameter matches too, you probably have the right one.

Each thread type and size has three corresponding taps, though you don’t need all three for through holes. They differ only at the point. The first cut tap has a long taper to help start the thread, the second cut has less taper and the bottoming tap has none, because it works when the other taps have already made the start.

As well as the taps, you need a tap wrench.

Cut the thread

When tapping a thread, it’s necessary to align the tap accurately with the hole so that they are coaxial. A crooked tap will not produce a good thread. In shallow holes it is less critical, but the deeper you go the more severe any misalignment becomes, and the tap will break. The first couple of threads set the alignment. Don’t try to pull the tap straight once the thread has gripped the tap, it’s too late then. You can sometimes correct it by drilling the hole bigger at its opening and re-starting the thread further in.

A good way to start the tap squarely is to grip it in the chuck of the bench drill used to make the hole. That keeps it on track, but you have to turn it by hand, using the drill lever to keep gentle pressure on the tap so it enters the hole and starts self-feeding. Once the first cut tap is securely held by the thread it has cut, you can switch to the tap wrench. Just wind the tap in as far as it will go, taking care not to bend it. Small taps break easily. Then, if it is a blind hole, change to the second cut, which will go further in, then to the bottoming tap, which will complete the thread to the bottom of the hole. Before bottoming, clear out the swarf.

Another method for aligning the tap is to drill a clearance hole in a bit of scrap metal or wood and clamp it above the hole for the tap. The tap will slide through the clearance hole, which will hold it square. The clearance hole must of course be drilled square.

Lubricate the tap

Lubricate the tap to give a better finish to the thread. There are special compounds, but oil will do. The swarf cut by the tap has to be broken up as you go. To do this, advance a little then turn backwards a bit, going two steps forward and one back. If you don’t, the tap can get locked.

Blunt taps are hard to turn and may seize. You can sharpen them with a narrow, round-edge grinding wheel, but it is easier to replace them. Watch for this if buying second-hand taps, they were probably disposed of because they are blunt.

Metric tapping drill sizes

Tap                        Metric drill               Imperial drill

3 mm × 0.5           2.5 mm –

4 mm × 0.7           3.3 mm –

5 mm × 0.8           4.2 mm –

6 mm × 1.0            5.0 mm –

7 mm × 1.0            6.0 mm                      15/64

8 mm × 1.25           6.8 mm                      17/64

8 mm × 1.0             7.0 mm –

10 mm × 1.5            8.5 mm –

10 mm × 1.25          8.8 mm                      11/32

10 mm × 1.0            9.0 mm –

12 mm × 1.75          10.3 mm –

12 mm × 1.5             10.5 mm                    27/64

14 mm × 2.0             12.0 mm –

14 mm × 1.5              12.5 mm                    1/2

16 mm × 2.0              14.0 mm                   35/64

16 mm × 1.5                14.5 mm –

Whitworth tapping drill sizes

Size (in)                  Tapping drill size

1/16                          Number Drill 56 (1.2 mm)

3/32                          Number Drill 49 (1.85 mm)

1/8                            Number Drill 39 (2.55 mm)

5/32                          Number Drill 30 (3.2 mm)

3/16                           Number Drill 26 (3.7 mm)

7/32                           Number Drill 16 (4.5 mm)

1/4                             Number Drill 9 (5.1 mm)

5/16                           Letter Drill F (6.5 mm)

3/8                             5/16 in (7.94 mm)

7/16                           Letter Drill U (9.3 mm)

1/2                             Letter Drill Z (10.5 mm)

9/16                           12.1 mm (0.4764 in)

5/8                             13.5 mm (0.5315 in)

 

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Turning metal on a wood lathe. Small items are possible

Aluminium finial turned on a wood lathe

Turning metal on a wood lathe is possible, even though the wood lathe is not designed for it. Lathes are designed specifically for either woodturning or engineering purposes, rarely both. Heavily-built engineering lathes work better than wood lathes. Their tool holder rigidly clamps the cutting tool and moves mechanically. But if you don’t have an engineering lathe and aren’t too ambitious, you can turn many small items in brass, aluminium or even steel freehand quite successfully on a wood lathe. The finial shown above was turned on my Graduate Shortbed lathe, mainly using a small gouge. It was threaded onto a bit of 12 mm studding held in a chuck, with tailstock support, and sanded to an acceptable finish. It is about 5 inches tall.

There are problems to overcome. Holding the tool so that it cuts steel is difficult. The hardness of the metal resists the cut, and the cut is very liable to ‘chatter’. This is vibration that leaves a rough or ridged surface on the work. Working freehand, accuracy is harder to achieve. Without a tool slide, accuracy comes from the turner’s skill. Making true cylinders or flat surfaces accurate to a thousandth of an inch freehand is not easy. But many items don’t need such precision.

Interrupted cuts, such as turning the corners off something, are particularly difficult freehand because it is hard to control the cutting tool. It is risky, too. Some wood lathes have a proper slide rest as an accessory.

Preventing chatter

Woodturners are familiar with the problem of chatter. When turning metal on a wood lathe it is hard to avoid. To prevent chatter, you need a strongly built lathe, with good bearings. It must hold the workpiece firmly, with minimum projection from the headstock. For example, modifying a drive centre while it is in the spindle taper is easy. A similar job held in a chuck is harder, because the metal can move away from the cutting tool.

Use tailstock support whenever possible. A Jacobs chuck will hold small items. Light cuts using a robust and sharp tool, with minimum projection over the toolrest, should then produce an acceptable result.

The tools

You can use a high speed steel woodturning scraper or a graver. A graver, which you can easily make yourself, was traditionally made from square section tool steel with a diagonal flat, leaving a long point at one corner. You could convert a triangular or square file, but a high speed steel tool bit would be better. A round high speed steel bar ground with a pyramid point would work. It would be similar to a woodturning point tool, but with a more obtuse point. Use a graver a bit like a skew chisel. Its edges (not the point) can plane off long, thin curly shavings from steel.

Brass likes tools with zero top rake, so responds well to scrapers. Tools leave a polished surface on brass. Aluminium turns with a graver or even a small short-beveled bowl gouge. Cutting speeds are lower than for wood, but because only small items are possible, the normal low-speed setting on the lathe is probably OK. Some metal alloys are more free-cutting and ‘turnable’ than others. A file will shape the item and remove chatter marks if necessary. Even on a lightweight lathe you can make simple shapes in steel using a file or a rotating grinding wheel held in a drill chuck.

Turning metal on a wood lathe is tiring, particularly with steel, because the tool must be held firmly up to the work. It helps to use a pivot pin in the toolrest to lever the tool into the work. This gives more control. If the workpiece is held rigidly, the pivot pin can help prevent chatter too. A heavy cut can increase it.

Safety when turning metal on a wood lathe

Turning metal freehand is hazardous, therefore precautions are necessary. It is essential that the workpiece is secure in the lathe. Chunks of metal flying out of the machine are even more likely to do you harm than are lumps of wood. Eye protection is a must. The swarf is sharp and hot – wood chips hitting your hand are annoying, but metal swarf can cut. Long strands could even catch your fingers and drag them in. Never clear away swarf while the lathe is running.

Turning with a scraper can make chips like little needles. They can get in your skin like splinters. But gloves are risky around moving machinery because they can catch and drag your hand in. Thin ‘rubber’ gloves that tear are safer. A bad dig-in could wrench the cutting tool badly enough to break it and perhaps cause injury. A file thrown back by the chuck jaws can injure you. They must always be used with a proper handle to stop the tang impaling your hand.

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Don’t forget dust extractor maintenance

This post is about dust extractor maintenance. It’s very easy to buy a dust extractor and forget about it. They are simple machines, but problems can grow slowly, so suction declines without you noticing.

Turning plastic

Not long ago, I made some wheels out of a commercial cutting board, one of the thick ones used in restaurants or on deli counters. I cut some squares from it with the bandsaw with no problems at all. I put each one in my self-centring engineering chuck and turned it to size and shape. A flat bit in the drill press made the holes in the middle. Back on the lathe mounted on a wooden mandrel to complete the turning. Job done. The plastic material, that I think may be polypropylene, turned very easily with a negative rake scraper, leaving a smooth, shiny surface off the tool. The only problem was the shavings. Long ribbons of plastic wound round the chuck, the mandrel and everything else, with the loose ends flailing as the lathe went round. So although there was no dust, I put the dust extractor on.

Later, it seemed to me that suction at the extractor inlet was not as good as it once was, so I cleaned the filter cartridge. This was a job I had been meaning to do for some time. There was lots of fine dust in it, blocking the pleated filter. I took it outdoors and used a brush and compressed air to get as much dust as possible out. I put it all back together and switched on. Much better!

Dust extractor fan guard

But was the suction yet good enough? Perhaps there was a blockage somewhere. My extractor is a cyclone unit, and at the outlet of the fan housing there is a grid to stop people putting their hand in and touching the spinning fan. I dismantled the ducting close to the housing to check it. Sure enough, long ribbons of plastic had passed through the cyclone and blocked the grid. It was surprising that air could get through it at all.

I knew what to look for, because once before when re-configuring the ductwork, I found the remains of a plastic carrier bag blocking the grid. Like the bag, the bird’s nest of ribbon was easy enough to remove. But this time I did my risk assessment and decided that although the grid removed one risk, it created another. The first risk was negligible to anyone with any sense, while the second was significant. So the grid had to go. I removed it, put the ducting back together and switched on. Now the suction is back to what it ought to be.

These are not the only times I’ve come across a problem like this. It’s possible for long splinters or other objects to get stuck at a bend so shavings build up, or for debris to accumulate at a low spot. And filters clog up from time to time. But often the drop in suction goes unnoticed, even if there is a vacuum gauge to check it.

So my recommendation is to make a point of scheduling maintenance, and to check suction at your dust extractor often. Whether you remove the safety grid is up to you. An objective way to measure suction would be useful. I shall have to consider a vacuum gauge.

Shavings trapped in dust extractor fan guard
Waste trapped by fan guard
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A homemade centre finder is easy to make and quick to use

One kind of centre finder on the market has a slot for a pencil to mark intersecting diagonals. These work well on squared timber, but are a bit slow to use on a batch of items. Another kind has a blade. You position the blank, tap it so the blade makes a diagonal line, then repeat. I’ve found that this type can easily start splits in the wood, and needs the end of the blank cut square.
The centre finder I used for a long time is simply a small wooden block. The block has a hole drilled that is a push fit for a short pencil. The hole is off centre. By turning the block on different sides there is some height adjustment. To use it, I put the spindle blank and the pencil block on a flat surface and mark a line across the end of the blank. Then I flip the blank 90 degrees and repeat to do all four sides. The result is a small square marked on the end of the blank, from which I can easily find the centre by eye. This is not super-accurate, but good enough for most purposes, and it is quick. I have several blocks in different sizes so I can pick the one most suited to the size of the spindle blank. The blank need not be square and the pencil block can mark cylinders equally well. The point of a nail works too, and stays sharp.
pencil block centre finder
Pencil block centre finder
adjustable centre finder
Adjustable centre finder

I’ve now made an adjustable version of the pencil block, with a pivoting arm to hold the pencil. The hole for the pencil has a slot through it and a pinch bolt to lock it.

To find the centre of a bowl blank, I usually use a hardboard disc of appropriate size. I have a lot of these in different sizes for marking out bowl blanks, and each has a small hole in the middle. I just lay one on the blank, and place it quite accurately by eye or touch. Then I mark the centre with a pencil through the hole.
chuck insert centre finder
Chuck insert centre finder
When I need more accuracy, I use a chuck insert centre finder. This is a short dowel with a steel point in one end. I turned the insert to fit inside the body of my engineering chuck. I put the chuck on the bench and adjust the jaws to be a sliding fit on the spindle blanks. The blanks must be square or cylindrical. A tap on the end of the blank pushes it onto the point to mark the centre. This is a good method to use when part of the finished item needs to be left square.
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The skew chisel. Learn to use it and see what it can do.

Lots of woodturners fear the skew chisel. Skews dig in alarmingly, seemingly without any warning or provocation. Some people don’t use them at all. But can you really call yourself a woodturner if you can’t use a skew chisel? It’s perhaps  the most useful tool of the lot for spindle turning, so it is worth persevering with it. Just watch Woodturner21’s videos on YouTube to see what the tool is capable of.
You probably already have some idea of how to use the skew chisel for cutting beads and planing a cylinder. You can find the basic principles in turning books and DVDs and I don’t mean to repeat them. All I can tell you is what you already know – that you need lots of practice – and show you how to get the most from that.

Tuning up

First, tune up your skew chisel. Although you can use different grinds, the default has a skew angle of about 70 degrees and a bevel length of about 1.5 times the thickness of the tool. A long bevel makes it easier to see what you are doing, though can make the chisel cut in deeper when you get a catch. Make sure the edge and the points are really sharp, and not rounded over.
A long bevel and straight cutting edge are easier for sharpening on an oil stone or diamond hone. It is OK to use either a straight edge or a curved one straight from a grinder. Try the edge on your thumbnail – if the edge or the point slides without biting in, it’s blunt. Make sure you keep the chisel sharp all the time you are using it, but grind away the sharpness from the long side edges of the tool so they slide easily on the tool rest.
If possible, use a strong, rigid skew of about 10mm square to practice beads (dealers sell these as ‘beading and parting tools’. They are easily ground to a skew angle), and one about 18mm wide for planing. Of course other sizes work perfectly well. But a short edge gives less scope for catching on a bead while cutting on the point, and a wider tool helps keep the long point clear on a cylinder.
Now check your tool rest. Make sure it is smooth. Rub it with a bit of wax to cut friction. Set it a little higher than for gouge cutting. This puts the skew’s handle in a more convenient place for you.

Set up the lathe

Have the lathe running slowly so you can see what is happening at the point of cut, and you don’t feel threatened by the spinning wood. Later you will probably want to use higher speeds. Put on your face shield, just in case.
If you are nervous, use a conical fixed centre (one without any teeth) in the headstock and a revolving one in the tailstock. Make a pilot hole about 6-8 mm wide and deep in the headstock end of the blank. The cone centre will give friction drive only, with nothing else forcing the wood round, and is safer than holding the wood in a chuck. You can adjust the tailstock until the friction is strong enough to drive the blank but it will stop turning if you cut too deep or have a bad dig-in.
Practice on soft timber.  Start with a blank you have roughed down into a cylinder of about 40mm diameter and about 150mm long. You may find bigger pieces intimidating, and long thin ones whippy, neither of which is helpful. Choose a blank that is straight-grained and without knots.

Practice

 Don’t try to make any specific item at first, just keep making beads and planing cylinders. Make beads of about 12-18 mm wide. Use a parting tool first to make a clear space either side of each bead for the chisel to work in.
Use the short point of the skew chisel for cutting beads, although it is possible to use the long point or the edge. Stick with the short point until you are happy with it – later you will try the long point and may end up preferring it. I think the short point is easier to start for many people.
The first few times, use a scraper to make a semicircular bead shape that you can then follow with the skew. The scraper seems easier, but don’t be tempted to keep on with it. When you see the difference in the surface the skew makes, you will understand why. Then, with the lathe switched off, present the skew to that rounded surface, first at the top and then moving down to the bottom of the curve, keeping the point in the proper cutting position as you go. The chisel will begin almost flat on the rest, and end on its side. See how you have to move the tool to keep the point in the right place. Repeat the movements round the curve, so your body begins to learn the action.
Although you will be cutting with the point, the bevel must float (not press) on the cut surface to support the tool. Twist the skew as you go round the curve to keep the point in the cutting position. The edge will be close to the wood, but don’t let it touch. If it touches when the lathe is spinning you might get a catch. When rolling the bead with the edge, the movements are slightly different.

Make a cut

When you are ready, switch on and take a cut. Go slowly so you can see what is happening. No rush. As slow as you like, if using a high speed steel chisel. Carbon steel can overheat if kept in the cut too long. Take a thin shaving. Steer the point all the way round the curve, repeating the movements you started to learn earlier. Try for a smooth, even cut and don’t put pressure on the wood.
Pay attention to the handle movements. They are what you are practicing. As you try to go round the curve, you may have a tendency to complete the movements either too early or too late. Either will make a poorly shaped bead.

Repeat

Don’t work too long on one bead, cutting too deep into the wood, because if the blank gets thin it will start to vibrate and could snap. Start a new one. You may find one side of the bead easier than the other. Concentrate on the easy side first, making half beads, until you understand the process and feel ready to change over. When you get a catch, start again on a fresh part of the blank. This is because the damage can interfere with the free movement of the skew.

Planing cuts 

Planing uses the edge of the skew chisel. Keep the long point up, clear of the wood. Have the cutting edge at about 45 degrees to the lathe axis, because that gives a slicing cut with the shaving coming off near the short point. The key is to keep the bevel floating, without pressure, on the freshly planed surface. It’s easy to let the handle lift a little, and immediately you will get problems.
At first sign of trouble, lay the handle lower. Feel for the position in which the cutting is smooth and quiet and easy. If the handle is too low, the edge just lifts out of the wood, so does no harm. As long as you long pay attention to keeping the long point clear of the wood, you should not get digs when planing. At the ends of the blank, let the cut run off the wood, not onto it, as there will be no bevel support at that point
When you can plane a cylinder without problems, you can try steering the cut to round over the end – this is another good way to make beads.