Category: Sharpening

Posted on by — 2 Comments

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 – newer models may differ. For a long time I used the machine for sharpening my spindle gouges.

I don’t recommend the Tormek 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 accessories 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 of the wood 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 often 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 to restore the edge 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 frequently. 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 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 a flat 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 on the wheel unless it traverses very slowly. 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, and of course it makes the wheel smaller each time it is used. 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 on mine (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

There are reports that the bearings suffer from rapid wear and corrosion. I have not found this on my machine yet.

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, so it has to be reset each time it is moved. 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 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!

Posted on by — 6 Comments

Sharpening gouges with a jig

Setting Varigrind cup position

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

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

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

Templates

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

 Duplicating an existing grind

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

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

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

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

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

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

 Changing the grind

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

Reshaping

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

The wings

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

 Sharpening gouges with a jig

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

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

Check the shape

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

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

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

 Making the templates

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

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

 

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

Distance template

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

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

Setting Varigrind cup position
Template to set Varigrind cradle position
Posted on by — Leave a comment

Platform sharpening woodturning tools

Platform sharpening is a quick and convenient method of sharpening woodturning tools using 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. You can use the platform for other gouges once you have the knack of swinging and twisting the gouge.

Setting the angle

There are a couple of problems to deal with in platform sharpening. The method often recommended for setting the platform angle is to match it to the existing tool bevel. You can ink the bevel where it touches the wheel for greater precision. I find the sound and feel of the grind when turning the wheel slowly by hand more helpful than the ink. When just the heel or the edge is in contact with the wheel, the sound is harsh and more grating. When the bevel rests properly on the wheel the feel is softer. Either way, copying the existing bevel works well, but is a bit slow, and liable to cumulative error. The platform angle will never be set perfectly. If there is the slightest bias in one direction the bevel angle will gradually change.

It’s more consistent, and quicker, to use a simple setting jig. The one I described in another post will maintain consistency. If the platform angle is always the same, any one tool placed on it will always be ground the same. The bevel angles may not be the same on different tools. This is because the edge of a thicker tool will be higher on the wheel.

Longer tools

The second problem is that 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, as you must to keep the angle. This means you may need platforms of different sizes. A large one to give stability to 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.

Platform sharpening with the Robo Rest

A minor inconvenience is that when platform grinding different tools at the same time, you may have to change the angle. The wheel normally has to come to a stop before you can do that. I use a ‘Robo Rest’ adjustable platform that I can set without stopping the wheel. A pin in one of the indexed holes locks the platform at any of the provided settings. Unfortunately this rest is currently unavailable.

Because it doesn’t reference from the wheel itself, the Robo Rest is most useful when using a CBN wheel. These don’t wear down, but other wheels get smaller with wear. With those, you have to move the platform closer to the wheel from time to time. Otherwise the tool angle will change. I found it very quick and easy to set the angle. It does its job well, with a repeatable grind. Its build quality is perhaps not as good as I would like. The platform is not perfectly flat, and there is some looseness in the locked platform due to the tolerance in the diameter of the locking pin. The maker points out that more rigid construction would add to the cost. Pulling the platform forward in use takes up the slack and makes the grind more consistent. The flatness is adequate for most purposes.

Posted on by — 2 Comments

CBN grinding wheel for sharpening woodturning tools

CBN (cubic boron nitride) grinding wheels have advantages for grinding woodturning tools. They are the latest must-have kit. 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. They are said to be very long-lasting. This means that any jigs used with them never need adjusting after initial set-up. They have a thin layer of grit on a heavy steel or aluminium wheel. They can be made with very fine grit (though these seem to be harder to find in the UK) and produce an excellent sharp edge on the tools. They are suitable for high speed steel and hardened carbon steel, but unhardened steel may clog them.

I recently invested in a 180 grit 200 x 40 mm CBN wheel from Optigrind and installed it on my VEM grinder, which though old is a reasonably good quality machine. Some small burrs from the old wheel flanges made them too tight for the new wheel. Holding the flanges in my woodturning chuck, I skimmed the bushing parts very lightly with a graver. They would have gone in as they were, but perhaps never come out again!

Update – I have now fitted a new wheel from Axminster. It runs true enough. But not all grinders are suitable for CBN wheels. Mine has large machined wheel flanges with keys in the shaft and labyrinths to keep dust out. The flanges don’t fit the wheels properly, and replacements of the right size and shape and with a slot for the key would be hard to find.

Wheel shroud

I was able to keep the wheel shroud in place. People say that CBN wheels are inherently safe. They say you don’t need to guard them because, being metal, they cannot burst. But this ignores the possibility of entanglement in the spinning wheel. It could catch long hair or loose clothing. Of course, those 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. So it’s best to keep them enclosed.

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

CBN wheels are aggressive when new

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 for sharpening. 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.

Wide wheels

The CBN 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 slowing down. It’s then the equivalent of a slow-speed machine (my grinder runs at high speed).

It’s nice not to have to dress the wheel to keep it clean. I hope that when the wheel is ‘run in’ and becomes less aggressive, it will be easier to use. UPDATE: The wheel has indeed become less aggressive and now I wish it worked quicker. But for sharpening, it’s fine. I still don’t notice that it gives a better edge than the stone wheel. I have a blue wheel on the other end of the machine and use that for gouges. I do think a CBN wheel needs to go on a good quality grinder, because it’s hard to eliminate any runout there may be.

Posted on by — 2 Comments

Grinding short gouges

During the years that I’ve been turning some of my tools have got shorter. Each grinding takes off just a little bit of metal and it adds up. I have never yet got to the end of a gouge or scraper. But there comes a time when grinding short gouges with a jig gets difficult.

Different jigs have different ways of clamping a gouge. Some have a peg that fits in the flute and some have a flat plate that bears on the sides of the flute. Either way, the jig has to lock the gouge in place and align it properly.

Modern gouges tend to have short flutes. This is a good thing, because it makes the tool more rigid. But if the jig clamp acts on the flute itself, how do you use it when there is not enough flute left to give the proper projection in front of the jig? When the flute gets short, the tool may have plenty of life left in it. But the jig clamp begins to bear on the up-sweep at the end  of the flute, and then later on the round surface of the shank. It no longer grips securely or aligns the flute properly.

There are several ways to overcome the difficulty of grinding short gouges. You can reduce the projection of the gouge from the jig, but this changes the bevel angle. You can learn to sharpen freehand – a nearly worn-out gouge is a good tool to practice with. Or you can re-shape the shank to suit the clamp. This is what I did today on two of my favorite bowl gouges. They were originally shallow fluted spindle gouges that I ground with a short bevel and round nose. They work really well for making small wooden bowls that aren’t too deep.

I ground down the upper surface of the shanks, leaving them flat and at the same level as the top of the flute sides. This would be enough for some types of jig, but mine is a Tormek jig that I use on the high-speed grinder. It has a small projecting peg under its clamping plate. So I mounted a metal-cutting wheel from an angle grinder in the lathe and carefully ground a groove along the middle of the flat part. I can now carry on sharpening the gouge as before, getting a lot more use from these two tools.

Scrapers

When scrapers get short, the handle starts to foul the platform rest at the grinder. To overcome this, you can make the platform smaller and cut off its corners so the tool can swivel for sharpening. Another option is to make a secondary platform that clips on the main one. Make it smaller, and thick enough for the tool handle to pass over the lower platform unobstructed. The secondary platform should be easily removed. If the lower one is steel, you might be able to use magnets, but they would attract the grinding dust. I use a bit of plywood with a length of perforated steel strapping as used by builders. This slides over the main platform. You have to alter the platform angle to allow for the extra height.

Posted on by — 4 Comments

Grinder platform angle setting jig

Sharpening is one of the essential skills for woodturning. Most turners use a grinder to sharpen tools, and platform sharpening is probably the best method for skews and scrapers. But each type of tool needs a different grinding angle, so a grinder platform setting jig for each angle is very helpful. For example, a skew chisel will usually have a more acute angle at its edge than a spindle roughing gouge, which in turn will have a finer edge than a scraper.

Each of these tools can be ground while flat on either the grinder’s own tool rest or a separate platform rest, which just has to be set to the correct angle. One way to do this is to blacken the existing tool bevel with a marker pen then adjust the platform until the bevel comes into full contact with the wheel, which is inched round by hand so that the ink removed will show the accuracy of contact. Or you can just match the bevel to the wheel by eye, looking from the side. But in either case, any error can be cumulative. It will be repeated and possibly amplified next time the tool is ground. This can lead to a gradual change in the bevel angle.

I use an easy-to-make grinder platform setting jig that gives a consistent, repeatable result very quickly. It consists of a scrap of plywood with two projecting screw heads that align it to the wheel rim, and a straight edge at the bottom to which the platform can be set. The jig is very easy to make and use. A different one is needed for each tool type and thickness (thicker blades contact higher on the wheel rim and because of its curvature will be ground to a sharper angle than thinner ones). Use plywood thick enough to take the screws in its edge without splitting, but no dimensions are critical. All you have to do is set the platform angle as you wish, perhaps copying an existing tool angle, then cut the plywood so it rests on the platform with its edge fairly close to the wheel rim. Insert the two woodscrews (as far apart as the wheel guard and platform will allow, and angled so they are radial to the wheel axis. Drill pilot holes to prevent splitting.) The screws are optional, but if used, they can be turned in or out to fine tune the fit or to compensate for wheel wear. If necessary, the inner edge of the plywood can be cut away to follow the wheel rim more closely.

To use the grinder platform setting jig, loosen the platform, place the two screw heads in contact with the stationary wheel rim, bring the platform into contact with the bottom of the jig and tighten up again. Every time you sharpen the same tool, or another of the same blade thickness, the angle will be just the same, making for quick results and saving tool life.

 

Posted on by — Leave a comment

More about the Alan Lacer skew chisels

I recently posted (12 October) about my new Alan Lacer skew chisels. I have had more opportunity to use them now and like them more and more. I think the smaller one may be more generally useful for most turners. I’ve been sharpening the edges with a diamond hone and thought today that I should jig the grinder to suit these tools. You could do a lot of honing before grinding is necessary though.

The grinding method advocated by Alan Lacer is the one I have always used for my curved edge chisels – set the grinder platform to the correct angle and simply swivel the tool while it is flat on the platform. You can see this on his website or on Youtube. This gives you an even bevel provided you keep an eye on the swivel limits so you don’t over-grind the points.

I was therefore interested to note that the grind used by the manufacturer is different. Although they are sold as Lacer signature chisels, the different grind gives them a different bevel and affects their use. I think they must be ground by twisting the blade instead of swiveling it, lifting the long point off the wheel to grind the short point, giving a more rounded bevel and making the short point very obtuse. It took quite a lot of work to bring the grind back to what it ought to be, and I think it could confuse a beginner.

Update – I have now changed the signature grind on these tools completely.

I made the setting jig for my grinder. Jigs are very important for quick and accurate repeatability. Unfortunately I cannot use the metal platform that came with the grinder as it is not sufficiently adjustable. I am now using the Tormek platform rest. I have made a block to set the extension of the arm, and an angle setting jig to position the platform.

 

Posted on by — Leave a comment

Sharpening Hunter tungsten carbide tips

A few days ago I wrote about trying to sharpen Hunter tungsten carbide tips. My attempts were not very successful. The tips are cupped, and I tried honing the sides and also grinding the groove in the top. I managed to improve the very blunt cutter but not to produce a ‘sharp’ edge. I think though that if the tip had been used on ordinary wood and not the abrasive stuff I am sometimes faced with, and had just lost its keenness, honing its side bevel in the lathe as I described would have been worthwhile.

I wanted to use the tip on some MDF today and found that even after my efforts it is really too blunt for freehand cutting. It makes hard work of it.

It’s time to write this tip off, at least in its original form. Other manufacturers offer flat carbide tips, which have a different cutting action. People find them very effective, as long as the right grade of carbide is used. For example, opinions of the Easywood tools are very favourable (I haven’t tried them myself). So I decided to convert the Hunter tip to a flat top. Better than just discarding it, there is plenty of carbide left, and they aren’t cheap.

I simply rubbed the tip on a coarse and then a fine diamond hone until the edge felt sharp and smooth. A little of the centre was also honed away in the process, but it went back in the Hercules tool with no problem. Back to the MDF!

I immediately realised that the forward tilt of the tip mounting gave too much negative rake for scraping with a flat tip. Lowering the handle until the tip was horizontal was much better. It cut even better with the tool tilted sideways and bevel rubbing.

So with very little effort I have a round carbide tip that could be used in any homemade cutter bar. Not as good as new, but too good to throw away.

Have you tried sharpening these cutters? Let me know!

 

Posted on by — Leave a comment

Trying to sharpen Hunter carbide tips

I recently posted about a Hunter Hercules tool I am using on the abrasive materials that I often work with. The manufacturer says the tips last a very long time. This may well be true when using ordinary wood, but not for me. I roughed out a number of items in mdf and some unusually abrasive hardwood, and the initial sharpness was soon lost. The tip kept on cutting while in my ball cutting jig in scraping mode, but was leaving a poorer surface. I am satisfied with the Hunter as a roughing tool until something better comes on the market. But the edge is now so blunt that the tool is hard to use freehand. The cutting edge feels quite rough, like a miniature hole saw.

The maker says the tips are disposable and cannot be sharpened. Sharpening Hunter carbide tips would be a useful option. It seems to me that if they were sharpened at the factory, it should be possible to sharpen them again. My first attempt involved honing the bevel. I put a bit of wood in a chuck and turned the end of it to a short dowel, just under the diameter of the tip, and faced off the end. I pinned the Hunter tip against the end of the dowel with the revolving tail centre. Then, with the lathe running slowly, I used a diamond hone to touch up the bevel. I found that a narrow hone was easier to keep in contact. A coarse hone took off visible carbide dust, then I polished it with a fine one. The bevel looked fine after this treatment.

I found that this had improved the cutting action somewhat, but on close inspection with a lens I saw that the edge was still quite badly chipped and uneven. More honing would eventually reduce the diameter enough to remove these chips, but the next thing I tried was to re-grind the inner bevel.

I used a very small ball-ended diamond cutter in my Dremel tool. This would not enter the groove in the tip because the tail centre was in the way. I drilled a small hole in the end of the dowel and used the Hunter fixing screw to mount the tip on the end of the dowel. It easily cut its own thread in the wood. As I write this, it occurs to me that I could just have turned the dowel thinner, reversed the tip, and worked from the other side. Anyway, with the tip on the dowel and the tail centre out of the way, I used the diamond cutter, with the lathe running slowly, to open out the groove a bit. Again, visible carbide dust was coming off.

I put the tip back on the shaft and tried a cut. The tip was certainly better than before. But not sharp. The lens revealed that the inner groove that when new had a mirror finish was now like a ploughed field. The diamond grit on the cutter I have is too coarse. The chips on the edge were smaller, but still there.

I shall use the tip for a bit longer, then try honing the top flat and putting it on a different shaft, one with a horizontal presentation.

My conclusion is that the manufacturer may be right. Unless you have a fine ball-end diamond grinder point to follow a coarse one (this would presumably leave the inner bevel as good as the outer), it is going to be difficult to bring the tip back to ‘as new’. I think I have prolonged the life of the cutting tip, but it is only good for rough work now. Perhaps I left it too long before attempting to sharpen. I may have to bite the bullet and replace the tip! Most turners would be happy with the edge life, and the cost of an occasional replacement would not be high, but the stuff I use them on will make disposable tips expensive.

Update – I have sharpened the tips now, but not back to new condition.