Homemade bowl reversing jaws

I sometimes use bowl reversing jaws to hold a bowl by its rim while shaping its foot. You can buy Cole jaws ready for use, but I recently made a set. Plywood quadrants are fixed to steel carrier plates that match the scroll chuck, and movable pegs fixed to the quadrants. The pegs form a circle that contracts onto the rim of the bowl. The pegs consisted of pre-drilled rubber bungs from a home-brewing supplier. They have a taper, giving them a dovetail grip. I drilled holes in concentric circles on the quadrants and fitted 8 mm tee nuts (the kind with prongs that are hammered or pressed into the wood). 8 mm bolts held the bungs firmly in place. There was a neat ring of 8 bungs ready to grip almost any size of bowl.

The bungs turned out to be a bad idea. I expected the soft rubber to give a non-marking grip and accommodate small positioning errors. But they had too much give, and anything but the lightest cuts would move the bowl in the jaws. Something had to be done, so I turned a set of wooden pegs to replace the bungs.

This was an easy job. I cut a number of short sections of a moderately soft timber (I used slices sawn 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 friction of the dead centre was ample to drive the piece and doing it this way ensured that the holes were central in the finished pegs. I turned them all to the same size as the bungs. They are about 30 mm long, 30 mm wide at the top and 26 mm wide at the bottom. I think shorter pegs would be fine, but I had the bolts the right length for that size. I used a parting tool and calipers to set the maximum and minimum diameters, a sharp spindle roughing gouge to cut the slight taper, and a skew chisel to square the ends so they would sit firmly on the quadrants. I used them to remove a temporary chucking tenon from the base of a Robinia bowl. They held much better than the rubber bungs, though this type of chuck is never the most reliable and heavy cuts cannot be taken. Tailstock support will provide more security. I can foresee that wooden pegs could mark or damage a fragile rim, so care will still be needed for that reason too. I have heard of people using a rubber sleeve over a wooden core to give just a small amount of give. Rubber tubing or even plastic hosepipe might work for this.

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Gouge vibration

Following my recent post on torn grain, there is another 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. The more they continue, the worse the vibration gets, and irregular ridges appear on the turned surface.

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 so the cut is more square to the edge. This lets the wood be sliced off before it gets to the bevel.
  • Take care not to push the gouge towards the wood. Any pressure necessary to stabilise the tool should be downwards onto 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 and use a bigger gouge. Small gouges can flex and set up vibration. If the gouge reaches too far over the tool rest, the effect of incorrect technique is magnified. The gouge is harder to control.
  • Make sure the gouge is sharp. Blunt tools make for hard work.
The cause of the problem described above is obvious. More baffling is when a gouge that is cutting smoothly starts to vibrate. As the cut continues, the vibration rapidly gets worse. When the surface is examined, there are pronounced spiral ridges.
The cause is pressure of the tool bevel on the wood. Any attempt to control the 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, in a feedback loop. The softer parts are cut deeper and the ridges get bigger and bigger.
  • When the vibration is felt, stop cutting immediately. 
  • Make sure the gouge is sharp, and adjust the tool rest 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. 
  • Make sure there is no pressure on the wood, but stabilise the gouge by pressing downward onto 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 so that the ridges come to the tool and are removed. 
  • Sometimes taking a heavier, more positive cut will help eliminate the problem.
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Preventing torn grain

Some people spend hours sanding a bowl to get a reasonable finish. But, apart from the tedium, 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, you have to cut the shaving in a way that allows it to separate cleanly without damaging the underlying surface. 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. The fibres are not cut, but torn apart. Tearing usually occurs either where the surface is changing from end grain to side grain with the rotation of the wood, or where locally disturbed grain opposes the cut. These are situations where a split can easily start and propagate.

To prevent torn grain: 

  • the shaving needs to be thin and weak during final cuts so it cannot transfer much force back into the uncut fibres
  • the angle through which it bends must be small
  • the uncut fibres must adhere to each other strongly enough to resist being split apart.

The first thing to do is of course to sharpen the gouge. The edge can then 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 can be highly 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 which bend and break easily without much leverage on the fibres not yet cut. Many beginners seem to be in a hurry to complete the cut 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, the final cuts should be as light as practicable. 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 tear-out than a skew chisel when spindle turning.

Make sure the bevel is properly aligned 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 allows you to optimise 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 reduce the pull on the fibres.

Present the cutting edge at a skewed angle. The effective bevel angle is at a maximum when it meets the oncoming wood square on. If the edge is skewed, the wood sees the sharpening angle 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.

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. Very little wood is removed on each pass. An ordinary flat scraper can also be used, on its side to skew the edge, and is easier to keep sharp than a gouge. Scraping like this will usually get rid of ‘macro’ torn grain but does not leave a burnished surface as a bevel-guided cut can.

A scraper flat on the rest can take a wide shaving, particularly if it has a curved edge that is similar to the curve of the wood surface. The shaving has to bend sharply as it is cut, but the top angle is too great to create a wedging action. Provided the shaving is kept thin and there is no vibration, a reasonable surface may be achieved. Too much tool projection can cause vibration, and so can thin walls on the bowl. Most woods respond better to a gouge.

Cut the wood ‘with the grain’. In a bowl, this usually means cutting the outside from bottom to top and 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 and this allows the gouge to cut them rather than break them off.

Some people 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 tear-out than others. Their fibres separate more easily. It is possible to apply shellac or other sealer to reinforce the uncut fibres and make them more resistant to splitting apart. 

If your best efforts still leave noticeable tear-out, you will need to sand to remove the damage. 120 grit would normally be considered 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 – but sometimes you can get away with spot sanding with the lathe stationary, then blending it in with the lathe running.



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Homemade hook wrench for faceplates and chucks

Screw chucks and faceplates are notorious for getting stuck on the lathe spindle nose. They have to be secure, particularly if you run the lathe in reverse, so can get too tight to remove easily.

Lathe manufacturers don’t always cater for this very well. They may provide a tommy bar, but these are often unsatisfactory. Unless the bar is stout it will bend, and if the hole for it is shallow the metal around it will distort. Soon, the bar becomes too loose.

A hook wrench causes much less distortion. They may not be easy to find in the right size, but adjustable ones are available.

It’s easy to make a hook wrench from steel rod about 3/8″ in diameter. The first step is to make a short peg at one end that will hook into the tommy bar hole in one of my screw chucks. I hot forged mine by making the end of the rod red hot with a blow torch, then hammering it into an L shape. I used the square edge of the vice jaws to make the bend a tight right angle. Using a file, I shaped the short arm to fit the tommy bar hole and trimmed it to about 1/4″ long. The arm needs to be at a right angle to prevent it slipping. Another method would be to drill a cross hole in the rod and rivet in a short bit of smaller rod.

Then the rod has to be bent to wrap round the chuck. It should go round about a quarter of the circumference, the rest of the rod remaining straight to form the handle. This is best done with the metal red hot, which would need a large burner or a small homemade forge, but the rod could be bent cold if you have a heavy vice. Make the bend to match the curve of the item if possible, but it is better to have it too tight than too loose. High carbon steel can be hardened and tempered, but I used a bit of scrap mild steel unhardened and it seems to be quite strong enough for light duty.

This wrench easily loosens my screw chuck – just a tap on the handle does the job.

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Platform sharpening

One method of sharpening woodturning tools uses a grinder or sander with a tilting platform. With the angle set, the tool simply rests on the platform while the grinder does its stuff. The process is extremely simple, and platform sharpening is the best method I know for scrapers, skew chisels and square-ended gouges (some people hone the tools to refine the edge, but most probably use them straight from the grinder). The platform can also be used for other gouges once the knack of swinging and twisting the gouge is learned.

There are a couple of problems to deal with. The method often recommended for setting the platform angle is to match it to the existing tool bevel, inking the bevel where it touches the wheel for greater precision. I find the sound of the grind when the wheel is turned slowly by hand more helpful than the ink – when just the heel or the edge is in contact with the wheel, the sound is harsher and more grating than when the bevel rests properly on the wheel. Copying the existing bevel works quite well, but is liable to cumulative error. The platform angle will never be set perfectly, and if there is the slightest bias in one direction the bevel angle will gradually change. It is better, and much quicker, to use a simple setting jig, like the one I described in another post, to maintain consistency. If the platform angle is always the same, any one tool placed on it will always be ground the same, although the bevel angles may not be the same on different tools because the edge of a thicker tool will be higher on the wheel.

Secondly, long and heavy tools are hard to keep in proper contact with the platform. They are too unwieldy. You need a light touch on the grinding wheel, which is not easy if you are holding the tool firmly in place on the platform. This means you may need platforms of different sizes. A large one for large tools, and a small one for short tools, which would have insufficient ‘reach’ to sharpen on a large platform because the handle hits the platform edge.

A minor inconvenience is that when grinding different tools at the same time, the platform angle may have to be changed, which means the wheel has to come to a stop for the angle to be reset accurately. I recently bought an adjustable platform rest that can be set without stopping the wheel. A pin is inserted into indexed holes, locking the platform at any of the provided settings. This method is best when using a CBN wheel, which doesn’t wear down. If a wheel gets smaller with wear it will be necessary to move the platform from time to time to maintain its relative position. I found it very quick and easy to set the angle and it does its job well, with a repeatable grind. Its build quality is not as good as I would like, with a top surface that is not truly flat, and significant play in the locked platform. The play can be avoided by pressure forward or back on the platform to take up the slack.  The maker points out that more rigid construction would add significantly to the cost.

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CBN grinding wheel

CBN (cubic boron nitride) grinding wheels are said to have advantages for grinding woodturning tools. Unlike conventional wheels, they don’t require dressing to clean and true them, so make less dust, and they don’t wear down to a smaller diameter, supposedly being very long-lasting. This means that any jigs used with them never need adjusting after initial set-up. They are also said to produce an excellent sharp edge on the tools. They are suitable for high speed steel and hardened carbon steel, but unhardened steel is said to clog them.

I recently invested in a 180 grit 200 x 40 mm wheel from Optigrind and installed it on my old VEM grinder. I removed some small burrs from the old wheel bushes that made them too tight for the new wheel. I did that by holding the steel bushes in my woodturning chuck and skimming them very lightly with a graver. They would have gone in as they were, but perhaps never come out again!

I was able to keep the wheel shroud in place. It is often said that these wheels are inherently safe and don’t need guarding because they are made of steel and cannot burst. But this ignores the possibility of entanglement in the spinning wheel. Long hair or loose clothing could get caught. Of course, they are dangerous around the lathe too. An unenclosed wheel seems likely to disperse grinding dust more widely, and because they take a long time to stop, they may come into contact with something while still spinning.

The wheel runs fairly true, but not as true as I hoped. I don’t know if the problem is in the wheel or my grinder. As the abrasive layer is very thin, it is not possible to true it up with a diamond dressing tool, as could be done with a conventional wheel. I found also that the grinding surface has some visible ridges and grooves. Not enough to significantly affect the grinding, but a little disappointing.

In use, the new wheel is fierce. I understand this is normal, and am expecting it to settle down as the grit begins to wear, but when sharpening a gouge I could see it shrinking before my eyes. It quickly re-ground a heavy scraper. The tools were sharp after this, but I can’t say they were sharper than the old ruby wheel achieved. Some people recommend a coarser 80 grit wheel, but I think that would be too aggressive. I would rather take it slower when reshaping a tool and have a more gentle and controllable grind when sharpening. The wheel creates fewer sparks than the old wheel, which might make it a little harder to judge when the grinding is complete. But as the jigs are accurate, a single pass over the wheel is normally enough.

The new wheel is wider than the old one. This makes grinding easier as there is less tendency for careless use to allow a gouge held in a grinding jig to fall off the side. But it does make the wheel heavier, so slower to wind up to speed and slower to stop. In one way, this is helpful as I can sharpen small tools as the grinder is running down, the equivalent of a slow-speed machine (my grinder runs at high speed).

It is nice not to have to dress the wheel to keep it clean, and my platform sharpening jig can be set accurately in position and doesn’t have to be moved as the wheel gets smaller. I hope that when the wheel is ‘run in’ and becomes less aggressive, it will be easier to use.

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Mobile bases

My workshop, like most, could do with more space. I am at the point where if I want anything new I first have to work out whether I can fit it in. To make things more manageable, I recently fitted mobile bases to some of the equipment, including to some big racks I built for materials and part-finished work. These items now live in the corners and get pulled out when needed. I have clear workspace in the middle. Luxury!

The first base was a commercial one for my table saw. It worked well enough to encourage me to go further. The second and third were pairs of rollers of the kind used for kitchen appliances, which I put under the bandsaw and the router table. They were much less successful as they can’t be steered easily and tend to get out of position. Also, their very small wheels tend to get stuck when there are shavings on the floor. I plan to get rid of them.

My next move was to get some heavy duty casters and build my own units. They are much less expensive than the commercial bases, just as useful, and much better than the appliance rollers. The simplest construction is a square of plywood for the item to stand on, secured in place, with a caster under each corner. But suitable casters are several inches in height and may make tools too high for easy use, and less stable.

A different construction can keep the equipment close to its original height, at the cost of putting the wheels outside the footprint. This is not necessarily a problem, and makes the item more stable. The casters are fitted under the ends of a pair of cross beams, either timber or angle iron. The item stands on a plywood square, but the plywood is suspended from the underside of the cross beams, between the casters. Spacer blocks between the beam and the plywood drop the plywood platform close to the floor. The increased overall height is then just slightly more than the thickness of the plywood.

I found that swivel casters on all corners are the easiest to use as they let the item turn on the spot. The casters need enough clearance to swivel without hitting anything. Larger wheels roll more easily if the floor is uneven. I find they don’t need to be braked, unless perhaps the floor is super-smooth and clean, or sloping. Wedges can be slipped underneath the item to stop it moving if necessary. A mobile workbench or any machine which will need to resist sideways forces would need to be wedged carefully to lift the wheels clear of the floor. Brakes on the wheels would have to act on the swivel as well as the wheel itself, and I suspect they would be less effective than the wedges. There are plans available for trolleys that lift the item for moving and let it down again when in place. These would be best for stability and convenience.

I tried casters with a single fixing bolt and also the kind with a steel plate that is fixed to the beam with screws or bolts. I think the plate fixing is easiest for fixing to plywood or timber.

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Homemade fluteless gouge

I mostly use ordinary gouges when making bowls. But I thought a ‘fluteless gouge’ might be interesting to try. I’ve watched Reed Gray’s videos on YouTube, in which he recommends them for finishing cuts, in particular across the bottom. It would be possible to use carbon steel, but I decided to make one as a tipped tool. I started with a length of round mild steel bar about 16 mm (5/8″) thick. On one end I filed a step, reducing the thickness to less than half the original diameter. I used a belt sander for some of the heavy work. I then cut a 16 mm x 30 mm piece of high speed steel from an old machine hacksaw blade, using an angle grinder with a thin cut-off wheel. Any thin, flat bit of HSS would do. I cleaned off the surface coating from the blade and made the step to fit the cutter so its top surface would be on the centre line of the bar.

Using a propane torch with flux and brazing metal from an Ebay supplier I fixed the tip to the bar. As an alternative to brazing, it should be possible to use epoxy glue to fix the cutting tip, specially if the tip is reasonably large and its surface roughened to hold the epoxy. Most propane torches can’t reach brazing temperature in free air, but I was using a Bullfinch torch that can achieve a higher temperature. It took a little time to melt the brazing metal. Then I just had to clean it up, removing surplus flux and brazing metal, shape and sharpen the cutting edge on the grinder and fit a handle. The edge has a gentle convex curve. 

The grinding angle is quite obtuse, like a scraper, and the tool looks like a scraper, but is not used like one. Instead, its bevel rubs with the tool inclined slightly upwards. Some turners use ordinary scrapers like that, but only if the tool is turned on its side, never flat on the rest as that could cause a severe dig-in. The fluteless gouge must also be rolled on its side so the lower part of the edge is nearly vertical and slices through the wood. It can work in either direction. It can only take a light cut, but as the videos show, it leaves a good surface even on difficult timber. Although the grinding angle is obtuse, the wood coming onto the slicing edge sees it as very sharp.

Its cutting action is like that of a traditionally ground bowl gouge, with the wing close to the wood surface. In each case the edge is nearly vertical. But the shape of the fluteless gouge puts the shaft nearly perpendicular to the wood surface, reducing any tendency to vibration. It works well. It does not replace the gouge, it’s just a finishing tool.

After I’d used it a few times though, the cutting tip suddenly fell off. The brazing had been completely unsuccessful. The tip had been stuck on only by the melted flux, because the steel bar had not been hot enough for the brazing metal to run under the tip. The bar was too big for the torch to heat properly in free air.

To make a better job of it, I stacked a couple of insulating refractory bricks, also obtainable from Ebay, to make a little hearth. This time, the cutter and the end of the bar were resting on the firebrick surface instead of being in free air. The refractory served to reduce heat loss. This was enough for the torch to quickly get them hot enough for the brazing metal to spread over both mating surfaces, ‘tinning’ them. I then put the cutter on the step and heated again until bright red hot. The brazing metal melted and the tip settled into place. I cleaned it up again and resharpened, and this time I’m confident the tip will stay put. The HSS is still too hard to file and seems unaffected by the heat. But there are different grades of steel, and to reduce the possibility of the tip being softened by the heat treatment it might be best to use low temperature silver solder instead of brazing rods.

I made a handle by drilling a push fit hole for the shaft in a bit of scrap and turning to shape.

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Improving lathe dust extraction

In recent weeks I have been improving 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.

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 cause air to be drawn into the system. They reduce efficiency, but are harmless. But the pressure after the fan is positive, so leaks in the box resulted in dusty air being blown out unfiltered. I therefore dismantled the box and replaced the filters with a new cartridge filter, much 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 outlet with about 5 feet of 7 inch pipe so it could go in a corner of the workshop which was otherwise dead space.

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. The lathe is a difficult machine to collect dust from, 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 much stronger.

I tidied up the branch line to the drill press and improved the 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.)

The final job was to make a new adjustable 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 position the inlet where it needs to be, it has to move in and out to accommodate different diameters of work, and along the bed to cope with different lengths. If the headstock swivels, the inlet must move with it.

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 can be locked 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.

So far, this arrangement is very satisfactory. The hose and bucket are out of the way, the inlet can be set close to the job, the hose is long enough to move freely, but not longer than it has to be, the stand is stable and very easy to adjust 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, so the bin fills more quickly than before. Possible improvements might be to make the arm telescopic and adjustable for height, but at present it seems fine as it is.

dust inlet stand
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Homemade disc sander for the lathe

Today I made a disc sander to use on my lathe. It fits in the dovetail chuck jaws, so can be set up and removed very quickly and easily.

I attached a faceplate ring to a bit of 12 mm birch plywood. I could just have made a chucking recess in it. I turned it to a disc of 180 mm diameter, as I have a lot of sanding discs that size. This is adequate for small work, but less than half of the diameter is usable in practice. A larger size would be better, other things being equal. I made sure the face of the disc was flat and running true. Then I turned a bevel on the back to thin the edge so I would be able to sand into recesses.

I covered the face with Velcro hook tape. I found 50 mm self-adhesive tape in a local haberdasher’s shop. I pressed it face down under weights for a few minutes to get a good bond, trimmed the surplus, then applied the loop-backed sanding disc. With self-adhesive tape it’s a good idea to keep the disc face down when not in use to prevent the tape curling. Velcro-backed sanding discs cling quite well to a coarse grit disc, so an alternative is to glue coarse abrasive paper on the face and use that to carry the Velcro backed discs.

Then I turned an ash dowel to be a snug fit in the tool rest holder (banjo), and made a 25 mm x 25 mm tenon on one end. My lathe tool rest has a 40 mm stem, so the dowel is very rigid. Finally, I drilled a 25 mm hole in a scrap of 25 mm thick MDF and fitted it to the dowel. This makes a robust sanding table, though without angle adjustment. Fine for the jobs I shall use it for. Thinner board could be laminated if necessary to build up the thickness. The dowel post can be positioned off-centre in the table so it will be fairly close to the sanding disc to ensure good support, particularly if the post is small in diameter.

A disc sander needs effective dust extraction. My extractor hose is there at the lathe and works quite well in its normal position, but would probably be better with the intake under the sanding table closer to the downward dust stream. It should be possible to make a shroud around the lower half of the disc if necessary.

I used a 320 grit disc running at about 1200 rpm to sand the edges and faces of a batch of about 40 small items of flatwork. The sander worked very well and will be a useful addition to the workshop.

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