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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 meant 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, plastic ribbon had blocked the grid. It was surprising that air could get through it at all. The long ribbons had passed through the cyclone.

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 this problem. 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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Hazards in a woodturning workshop

There are some significant hazards in a woodturning workshop. Some of them are specific to turning and some 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, 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 you 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 which activity is free of any hazards?

Some of the risks can be minimised by well-known 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. But 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 fragments will then fly in a straight line 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 held securely, 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.

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 poorly 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.

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

Tie back long hair when using any machinery with exposed rotating parts. Don’t wear long sleeves or loose clothing or jewellery that might catch. Don’t take chances with poorly gripping chucks or 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. Don’t use timber with dangerous cracks or bark inclusions or rotted areas. Keep out of the ‘line of fire’. 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. Don’t ever 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. Don’t turn large heavy pieces until you have plenty of experience of smaller ones – learn to walk before you run. 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.

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). 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. You should 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 at the moment when you are shocked. 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 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 or be dropped. 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 come into play, 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 lamps 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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Dust extraction upgrade

I have recently improved my dust extraction system. For a long time I have used a 2HP cyclone system with four felt tube filters hanging from a homemade plywood distribution box. I had a 7 inch pipe running across the ceiling with smaller branches to the lathes, bandsaw and drill press. The branches to the two lathes were 5 inches in diameter.

Filters

This system worked quite well, but had some problems. The cyclone and fan unit were OK, but the filters took up a lot of space, and the distribution box leaked. Leaks before the fan reduce the suction. They cut efficiency, but are harmless. But the pressure after the fan is positive, so leaks in the box result in dusty air blowing out unfiltered. There isn’t much point in having a dust extraction system if it does that!

I therefore dismantled the box and replaced the filters with a new cartridge filter, smaller but just as effective. While doing this I found the remains of a plastic carrier bag that had been sucked in, gone through the cyclone and fan and stopped at the fan outlet where there is a grid to prevent people putting their hands into the fan. It had created a partial blockage.

The new arrangement gave me more badly needed floor space. Rather than put the cartridge filter next to the cyclone, the normal arrangement, I extended the cyclone outlet with about 5 feet of 7 inch pipe so it could go in a corner of the workshop which was otherwise dead space.

Ducting

The next issue was the branch line to the lathe (I am now using one lathe instead of two). By reducing the duct diameter from 7 inches to 5, I had been unnecessarily reducing the air flow. Dust extraction is difficult at the lathe, so the more air flow the better. As the extractor has a 7 inch inlet, I decided to extend the full size duct right to the lathe. I was also able to shorten the duct and eliminate some bends which were reducing the air flow. The ducting is smooth bore metal, with the last 3 or 4 feet in 7 inch flexible hose. I put a metal blast gate at the point where the hose starts. The suction now feels stronger.

I tidied up the branch line to the drill press and improved the dust extraction from my Startrite 352 bandsaw. This saw, being an older model, had no proper provision for connecting to the extractor. I cut a hole in the sheet metal of the lower stand and bolted on a flanged adaptor for a 5 inch hose.

I fitted a dust level sensor to the lid of the collection bin. This turns on a flashing light when the bin is full. I have only once allowed it to overflow and fill up the filters, but now I no longer have to keep opening the bin to check. (Update – I have found this sensor unit unreliable and very prone to showing the bin full when it isn’t. I no longer use it.)

Adjustable inlet

The last job was to make a new adjustable dust extraction inlet for the lathe. The inlet has to be as close as possible to the point where the dust is generated. The suction falls off very rapidly with distance, and has to compete with air movement caused by the spinning wood or sander. It’s easy to get the inlet close enough for small spindles. But for faceplate work and larger spindles it can be difficult. To put the inlet where it needs to be, it has to move in and out to accommodate different diameters of work. It also has to move along the bed to cope with different lengths. If the headstock swivels, the inlet must move with it.

Movable stand

I made a movable wooden stand for the inlet (see sketch below). A wooden post is held upright by standing it in a bucket of loose gravel on the floor behind the headstock. I fixed two boards to the post in a V formation, buried in the gravel to anchor it. The post has a projecting arm at about the height of the lathe spindle, at the end of which is a wooden cradle to support the hose, which hangs down from above.

I made the cradle to fit the hose, and strapped the hose to it with bungee cord. The cradle swivels on a bolt and locks to  keep the end of the hose turned to the workpiece. I can pull the arm to turn the bucket to any position, or slide the bucket to move the inlet along the lathe bed. The weight of the gravel keeps the bucket and post firmly in position but it is not heavy enough to make adjustment difficult. It would be harder if I did not have access to the back of the lathe.

So far, this arrangement is very satisfactory. The hose and bucket are out of the way and the inlet can move close to the job. The hose is long enough to move freely, but not longer than it has to be. The stand is stable, very easy to adjust in and out, and cost next to nothing. The only slight problem is that because of the better suction, more of the chips are going up the pipe along with the dust. This makes the bin fill more quickly than before. Possible improvements might be to make the arm telescopic and adjustable for height. That would avoid having to move the bucket. But now it seems fine as it is.

dust inlet stand