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Waveney & District Woodturners |
Tool Tips and Techniques
THE ENJOYMENT OF WOODTURNING by Mike O' Connor Part 1 Or is it?, how many of you would own up to say I really enjoy it, or I wish I could get a finish like x, y or z then I really would enjoy it. This article is not intended to upset anyone or to single out individuals or groups. The intention is to offer help and advice, after all that is one of the reasons for having a woodturning club. What I have to offer is a little over 20 years of turning experience, including many hours of blood sweat and tears trying to emulate the work of some of the great names in woodturning I have had the pleasure of meeting or reading about. My background is machine tool engineering, working to extremely fine tolerances and somebody up there gave me an extra dose of perfectionism when they dropped me on this un-expecting earth, so I guess I have a little experience which I am happy to pass on and any comments or arguments you want to add to this article please feel to free to do so on the members pages as I might be wrong, you could be right and others can learn from it all. When I see work exhibited on the table at club meetings, I sometimes feel if only this person had turned this object with sharp chisels it would have been so much nicer. I'm afraid no matter how hard you try you inevitably can not disguise poor turning. This is not related to the design of the object, this is another on going subject and nothing to do with this article. I am referring simply to the removal of the unwanted portions of the timber and how you go about doing it. What are the signs of poor turning? – torn grain, gouge marks in a ring formation in the bottom of a bowl, marks left by the 40 grit paper you used to try and correct matters, sharp edges missing where the sanding has been so excessive the edge is now a radius. Soft wax deposited in the nooks and crannies left by the effects of poor turning, there are more but I think that's enough for you to get the idea. You can sum it up in one word “CRISP”. A nicely turned piece will look and feel crisp. How do I know all this? Easy 'cos I’ve done it!!!!!!! How do you produce a “crisp” piece of work? In principle it is easy, in practice, well it takes lot's of it. The solution is sharp tools. Maybe I should expand this a little, sharp means correctly ground with a sharp cutting edge, just so that we are crystal clear on terminology there are some words you are probably fed up with reading about and couldn't really care about as long as wood is being removed. But unfortunately you do need a little understanding of the terms. CONCAVE, a hollow ground below the top face of the cutting edge. CONVEX, a curve ground below the top face of the cutting edge FLAT, no curve in or out BEVEL
A selection of some of my turning tools. Note the flat-ground bevels.
Before we start on the actual sharpening process a word or two about the grinding medium, at the moment we are talking about grinding wheels, but this will change as we move on, don’t worry this is not going to get technical nor do you have to learn about it, but the very basics are worth knowing about. If you purchased your bench grinder from a budget, non-woodturning source you may need to take a little more notice. Strange as this may seem to efficiently grind soft steel (carbon chisels) you need a harder grinding medium, if you grind harder High Speed Steel chisels (most common today for turning) then you need a softer grinding medium, if you grind Tungsten Carbide steel (very hard) then you need an even softer grinding medium. Back to the budget bench grinder, it has probably got gray coloured grinding wheels and if your chisels are High Speed Steel, then I’m afraid it could be time to purchase some new wheels from a woodturning stockist more suited to the job in hand. So we have hard wheels for soft steel and soft wheels for hard steel. After that there is only the grade to worry about, course, medium or fine. If you want to know more it may take you a week of bed time reading to cover the basics and I’m sure you’ll find a good book in the library on the subject, I can’t imagine any of you going this far. The simple answer is ask your stockist which wheel is most suited to your needs. Be careful on your choice of grit size (that’s the course medium or fine) it is difficult to be precise and recommend a grit size to you. The lower the number the courser the grit, much the same as your abrasive paper. A 40 grit wheel will remove vast amounts of steel in a very short space of time, whereas an 80 grit will only remove a small amount of material, it will also heat the tool edge up very quickly, anyone going to own up to seeing that red glow along the edge of your chisel whilst grinding. The reason is either you are pressing to hard trying to remove to much steel or the wheel is clogged, yes they get clogged, imagine a wheel 25mm wide of 40 grit and the same wheel of 80 grit, this means you have got twice as much grit in the same area on an 80 grit wheel, and what is between the grit?, a mixture of air and bonding agent, don’t worry about the bond, that’s another boring old subject, lets call them voids between the grit, a 40 grit wheel has far more voids the an 80 grit wheel therefore you can fill it up with more waste from your chisel, when it gets full it is clogged and will tend to rub creating friction and heat rather than cut. If you are financially stable you can purchase 2 new grinding wheels one with a low number for shaping and the other with a higher number for fine finishing, if you are on a budget go for something in the middle around the 60 to 80 grit size. Why not just stick to the course one? If you imagine a course grindstone as the rocky face of Everest with huge boulders, then that pattern of boulders is transferred to the cutting edge of your chisel so instead of having a continuous cutting edge you have a series of sharp points which a chunk of Elm will wear away very quickly. If you have the gentle pebbles on the beach at Kessingland, the fine wheel, then your cutting edge will have many cutting edges and last longer. Your grinding wheels will need cleaning regularly, no you don’t put them in with the weekly wash! this does a couple of things, try grinding half a dozen bowl gouges on a 80grit white carborundum wheel, then follow that immediately with a 30mm wide skew chisel (sorry Colin I meant beveled scraper), great if you like the edge of your skew curved. The term used is “DRESS” you dress grinding wheels, again without burdening you with more than you need to know the simplest method is with the point of a diamond wheel dresser move it squarely across the face of the wheel and it will take off the ridges, remove a layer of the clogged grit and leave you a virtually new grinding wheel. The down side is the wheel progressively get’s smaller and your concave bevel get’s a smaller and smaller radius, which does make it more difficult to use. At this point I should separate out those of you who use a wet stone grinder, as you will use a grader to change the same wheel from course to fine, but let’s not get too technical. So with all this information we can move on to the next stage which I will cover in part 2. Or else you will get bored with the subject, but hopefully some of you will nip out to the workshop and have a closer look at your grinding wheels. THE ENJOYMENT OF WOODTURNING Part 2 Hopefully you now have your grinding wheels sorted out, either new one’s more suited to the steel you are grinding or nicely cleaned and true. The next issue is a support to rest the chisels on while you grind them. Some of you may have seen the odd professional turner grinding chisels supported by one hand and manipulated with the other without using any form of tool rest at all. This is achieved by the fact the tool bevel is already the curvature of the wheel and with care and a light feel it is possible to “feel” the bevel against the grinding wheel and gently manipulate the tool until the sparks just come over the cutting edge of the chisel and the job is done. A vibration free grinder and a lot of practice is what makes this method achievable. For most of us some form of guide to set the correct grind angle is almost a must. The tool rest’s supplied with a budget grinder inevitably are a little springy in use and the usual adjustment is in and out only with no allowance to alter the angle. For the woodturner who wants to get their chisels ground with the minimum of fuss, then one of the many adjustable tool rests with various jigs on the market is almost a must. It is not my intention to run through the various types on the market. Hopefully this article will give you a little more insight into what to look for when making your purchase. As the old saying goes “you get what you pay for”, leaving wet stone grinders aside again, as these tend to have a set of jigs and fixtures available to grind anything from a pair of scissors to a hefty finger nail bowl gouge. You are probably stuck with buying jigs from the original machine manufacturer. However with bench grinders this is not the case. Starting with the grinding angles you are most likely to use in woodturning are as follows:- 15° for Skew chisels 30° for parting tools and spindle gouges 45° for bowl gouges, some scrapers 90° for shear scrapers Before you all hit the e-mail send button yes there are many more angles in between these that you may be using, for instance, continental gouges ground at 60° are a joy to use, scrapers at 80° degrees are fantastic in some timbers, a bowl gouge ground at around 60 or 80° is great for those deep awkward bowls where the rim get’s in the way. In other words probably the minimum you will require is as listed. The next important point to look for is that in use the tool rest is stable; you do not want anything that flexes under the lightest touch. The final thing to look for is the width of the actual tool rest table area, ideally it needs to be much wider than the grinding wheels and from a safety point it is as well if the tool rest has a cut out enabling the wheel to enter in to the tool rest area (see photograph). This will allow you to grind safely such tools as a round nose scraper with out fear of it dropping off the tool rest.
Budget is probably going to be the governing factor in the early stages. Quite a good tool rest can be purchased for around the £20 mark, it will adjust by means of a pivot point in and out and lock in any position.
A second pivot point under the table section allows the table to pivot independent of the base therefore any grinding angle you want is available, even to negative angles (but not advised). With care and a lot of practice you can grind finger nail gouges on this type of tool rest but the finished grind and shape is in the hands of the turner. The only way you can make repeat grinds is to make up a series of MDF type templates which sit on the tool rest table once you have established the grind angle, e.g.45° slide the rectangular bit of MDF past the side of the stationary grinding wheel, mark with pencil the curvature of the wheel and carefully cut the area along side the wheel away. Remember to felt tip pen the angle on the template (45). Repeat this for all the other angle’s you require. Now to repeat grind a 45° angle, hunt through the shaving to find your 45 template, loosen the 2 locking handles just enough so that nothing flops around, with the grinder switched off adjust the tool rest so that the template has no visible air gap between the curvature of the wheel and the tool rest. Make sure the tool rest is close enough to the wheel to prevent tools or fingers getting down there and secularly lock it in place and you are ready to grind. The disadvantages are that inevitably when you tighten the locking handles the base arms or the table moves and you start all over again, they are not as stable as other types with pre set angles, and if you have difficulty with finger nail profiling then it probably is not the jig for you.
A second type has a similar table area as above but normally made from a much more substantial cast iron.
When this tool rest is locked in place there is no movement whatsoever, it consists of a base unit and a stem and table unit, both substantially made, it has pre-set indents for the list of angles above, except it will not go beyond the 45° or 15° angles. Setting any of the preset angles is simple, quick and accurate. Any angle between the 45° and 15° pre-sets can be made. As with the budget unit the grinding of finger nail gouges is relatively easy but it is in the total control of the operator, so if you are not at ease with grinding then this may not be the jig for you. As for other tools such as parting, scraping, ‘U’ shaped gouge grinding, you really can not go wrong and it is a delight to use and easy to set up. This type of tool rest is going to take you in to the more serious money, probably at least 3 times the budget system. Depending on your skill level and what you are looking to turn you may even need a separate finger nail gouge grinding jig. The disadvantage in the main is that unless you make your own secondary table to sit securely on top of the original at 90° to the wheel you can not grind 90° shear scrapers or the swivel tips which are so common these days.
The final type of tool rest system we will look at does have a name of “Universal” it may be of advantage to some turners in as much as you can purchase it in stages, from the basic adjustable table only, the finger nail gouge jig only or the whole jig to do everything, naturally there is a price advantage if you buy the complete Universal jig system at around £80. The basic at about £45 and the finger nail profile jig at about £50. The jig is made of steel, rigid, can be fitted to any make of bench grinder. The slight down side is that there are no preset angles for the universal table, you either use setting jigs or eye the bevel of the chisel against the stationary grinding wheel. The finger nail profile jig after a little practice is very easy to use and regrinding once you have established the setting up is faultless.
The last option if you are budget conscious is to manufacture your own, it is not as difficult as you may think, Bear in mind what we have covered above, safety, rigidity, preset angles. I would advise against making tool rest tables from something like plywood, firstly the surface is to soft to allow the tools to move and secondly the grinding wheels remove a lot of red hot glowing sparks, these can build up on the tool rest and the draught of the wheels going round gentle blows these to start a small smouldering fire, which may turn in to a blaze after you leave the workshop. For this episodes visit to the workshop as well as looking at your tool rest have a good look at the area your grinder is situated in. Some I have seen have the bench covered with a good liberal layer of woodturning shavings (they are usually the experienced ones) others plus the experienced also have a good coating of sanding dust. Sparks from a grinder will sit and smoulder for quite a long time in the right dusty conditions before bursting in to flame. Consider sitting your bench grinder on a melamine work top (white is a good background) or even have a sneak look in the oven in doors there might be a large shallow baking tray you can sit it in. Finally do not Hoover up around your grinder immediately after a grinding session, I did this once, Hoovered up a few glowing embers and the draught inside the vacuum cleaner soon fanned those in to a good blaze. Do remember in a woodworking shop dust is not only a hazard to our health from breathing, dust extractor ducting can create static electricity which given the right conditions with a good supply of fine airborne dust, does n’t just burn, it explodes. A couple of correctly fitted earth wires should reduce this risk. Thankfully this does not occur very often and there is probably no need to go any further than cleaning up the dust round the grinder but there is nothing wrong in just putting out a reminder now and then and having a glance around your own workshop. While we are on the subject of the grinding area, if you tend to bend forward to grind your tools consider packing the grinder up, even up to chest height, you’ll be surprised how much easier it is to grind if you are standing upright (it’s better for your back as well). It should not be lower than your lathe spindle height, which should be near the centre of your elbow standing up straight with elbow bent at 90°. Follow the manufacturers instructions when mounting your tool rest / jig for optimum grinding accuracy. There are many more jigs on the market all working round a similar principal. Next part we will look at a totally new sharpening system without grinding wheels.
THE ENJOYMENT OF WOODTURNING
Part 3 We are almost at the point of actually discussing the physical grinding of your chisels but before we do I’ll briefly discuss a relatively new concept on the market. Up to this point I have steered clear of mentioning manufacture’s names as I do not propose to make any judgments for or against any particular brand. In this instance there is no point in hiding the name as there is currently only one on the market that I know of, the equipment is the Robert Sorby ProEdge Sharpening System. Although I said in the first paragraph that this is a relatively new concept, this relates to the fact that it is new to us non professional Woodturners, Robert Sorby I believe have been using a large industrial version for many years. The following section is the exact wording taken from Sorby’s web site. ProEdge is a revolutionary sharpening system introduced by Robert Sorby. In fact, the concept is far from new as the ProEdge largely replicates the tool sharpening system which has evolved in the Robert Sorby factory over many, many years. This compact system is now available to woodworkers whether operating in a large workshop or small shed.
Central to the ProEdge is an abrasive belt which is a quick and efficient method of putting a keen edge on each and every tool. The cool running belt avoids any overheating. The ProEdge comes complete with aluminium oxide and zirconium belts with a selection of sizes in those materials and ceramic also available. Belts are the only parts that need to be replaced and can be purchased at a minimal cost. The system comes with an angle setter which allows the user to accurately locate most of the common sharpening angles required by woodworkers. However, the user can easily set his own angle if he wishes to move away from any of these common pre-set angles - 15, 20, 25, 30, 35, 45, 60, 80 and 90 degrees. The angle setter ensures that the same angle can be achieved accurately time after time. There is no complex setting up involved. In fact, the ProEdge can be used straight out of the box. The ProEdge is ideal for those who need to sharpen carving tools, bench chisels, framing chisels, turning tools, plane irons, router bits, garden tools and much more.
As you have read, Sorby start off saying the abrasive belt is central to the system, well I guess as what we are looking to do is remove unwanted metal and produce a fine cutting edge then the abrasive is central and all important. If you refer back to part 1, I mentioned the various types of grinding wheels available which if you really wanted to follow it up can get extremely technical and bewildering. On the ProEdge Sorby have made it nice and easy, 3 types of material abrasive bonded on to a flexible belt in course and fine, Aluminium Oxide, for carbon steel, 60, 120 & 240 grit Zirconium, for high speed steel 60 & 120 grit Ceramic, (seems to grind anything) 60 & 120 grit. So if you are a woodturner with a set of high speed turning chisels and you don’t use to many bench planes and other wood working cutting tools then you would probably choose the Zirconium belt, 60 grit for shaping or removing nicks if you dropped it on the concrete floor and 120 grit for that fine sharp finish. The cost of 2 Zirconium belts is a tiny fraction of a good quality 5” white aluminium oxide grinding wheel, nor will you need to invest in a diamond wheel dresser (last paragraph part 1). Everything I discussed about tool rests in part 2 is wrapped up in the section Sorby refer to as “the system comes with an angle setter”. I think if I had written Sorby’s sales blurb I would have put “AT THE HEART OF THE SYSTEM IS THE TOOL REST”. You really have to be pushed to fault this, it is every thing us Woodturners could wish for, 9 preset angles and once it is set I defy even the heaviest handed of you to move it or even flex it. If that’s not enough pre-set angles you can set it at any angle you want in degrees, minutes and seconds between 15 and 90 degrees. You do not need to go fudging around in the shavings to find a spanner to adjust the rest Sorby have cleverly built it in and it won’t fall off. With a conventional bench grinder the normal practice is either to bash away on one wheel for shaping followed by the fine finishing. This becomes a bit of a compromise as you want a finer wheel to give the last final grind, therefore heavy shaping either takes much longer or the final finish grind is not all it could be because the wheel surface is ruined. Alternatively you need 2 wheels one course and one fine. The chances of them wearing at the same rate is remote so one wheel will be slightly different in diameter than the other and you will grind a second bevel. You will either have to have 2 identical tool rests or have the ability to change the rest from one wheel to the next. This problem is completely eliminated with the Sorby system, slip on the 60 grit belt, re-shape your chisel to the precise angle of the preset tool rest angle, remove the 60 grit belt, slip on the 120 grit and complete the finish grind. It takes about as long as you have just taken to read this bit to change the belt. Those of you who use a belt sander will be familiar with belt tracking (making the belt run in the desired position) In practice I have found that I can change any of my 7 belts and maybe only one of them will need a little tweek on the well designed tracking mechanism. You do not have to worry about belt tension Sorby have taken care of this for you with a simple but effective lever, cam and spring device. Sorby go on to say In fact, the ProEdge can be used straight out of the box. This is absolutely true, but I have to admit my machine is no longer as it came out of the box, it is what I call personalised as is the case with all my machinery. It is probably my days spent as a machine tool engineer, I can never resist carrying out small personalised improvements and providing you do it safely and fully understand what you are doing I see no harm in it. If you are a little worried using a high speed bench grinder or just can not get on with tool grinding for what ever reason, or maybe like me you can not resist something new then maybe this could be the sharpening system for you, but be prepared to dig deep in to your pocket this excellent bit of kit does not come cheap. But then neither do some of the wet stone grinders. Having now used the Sorby ProEdge for about a month I can not fault it. In part 2, I mentioned the finger nail profile jig costing in the region of £50, if you do purchase a ProEdge system you can buy it with various jigs including the profiler as the “plus” model or you can buy the base model and add the profiler as an extra at around £38. If you use bowl or spindle gouges and you are not an expert free hand grinder then the profiler is almost a must and you will not be disappointed. OK I like new toy’s, but the real reason for my purchase of the ProEdge was to get rid of the concave bevel. Now I’m going to expect an awful lot of issues posted about this comment. Unfortunately my little drawings of the bevels described as concave, convex and flat in part 1 did not reach you, but hopefully you understand the difference between each. The big difference with the ProEdge System is that it produces perfectly flat bevels, so what! some of you may and will undoubtedly say. In my opinion on any cutting tool (as against a scrapping tool) if you want that smooth glossy finish on your work before you abrade it then the bevel is as important as that scalpel finished cutting edge. To give you an example, and you can go out to your workshop and try it. I was at a friend's workshop the other day and we were playing around having fun on the lathe making a box with the inside of the lid turned, the material was a very nice piece of dry Yew I was using a concave ground 6mm deep flute bowl gouge and taking a flat cut across the face, in the light from the angle poise light I could see the beautiful gleam of the polished Yew appearing behind the gouge, I stopped turning about 20mm from the centre and from the finish of the cut back about 4mm I could see a discoloured ring. Not being quite fully professional yet I thought Oh that’s not very good so I took another cut about 1mm deep straight across the face, stopped at the 20mm mark, same result. I stopped the lathe to see what was going on. The answer was the heel of the bevel which was about 4mm from the cutting edge was rubbing the surface as it should and polishing the wood as it went but by stopping abruptly at the 20mm mark the last 4mm did not have the bevel rub on it due to the concave grind. By accident I wonder if I have proved that my purchase was worth the expense, because with a flat bevel this will not happen. OK I think I have gone on enough about grinders, wheels, grades, dressing, toolrests, etc. etc. At the end of the day you are probably going to use what you can afford and what suits you best. The one thing I can assure you, whether you are using the rather expensive ProEdge System, or a Far Eastern made bench grinder you got change for from a £20 pound note, if you put some of parts 1 and 2 in to practice on your grinder, even if it is to lift it up higher, you will enjoy your turning even more if you are doing it with sharp correctly ground chisels and if we can take out the mystique of sharpening then you will not hesitate to keep your chisels sharp. Why do I feel that a flat bevel has any benefit over a concave bevel? Again this is a personal preference gained over many years of experimentation, given that “THE BEVEL MUST ALWAYS RUB” as a beginner you should be starting your cut with the heel of the bevel rubbing the revolving work, slowly lift the chisel handle and a shaving starts to appear over the cutting edge, lift it more and you get a larger shaving drop it, a smaller one. With a concave bevel there is nothing between the heel rubbing and the edge cutting, this is generally highlighted for the beginner with the skew chisel, one minute it is doing nothing the next it has cut a deep screw thread in you work piece, a few expletives are uttered and back in it’s box goes the skew chisel. With a flat ground chisel you can actually have far more control simply because the bevel is constantly in contact with the work piece. The first unexpected difference I found with all my chisels was that initial bite I used to get whether it be a spindle gouge, bowl gouge, skew chisel, bedan or parting tool had gone. The chisel just enters the work piece so clean and smooth. I also found that the inevitable minute ripple effect left by a bowl gouge going across the bottom of the inside of a bowl had gone, I also find it easier to turn across the face of the work piece with a gouge and maintain it absolutely flat, whereas with the concave bevel it had a tendency to lift off the work and leave a convex face. I reground my scrapers from 45 to 80 degrees, they cut just the same but with minimal lift of the handle, shear scrapers are now ground at 90 degrees which enables you to press the bevel against the work piece and leave a polished smooth finish. Don’t be put off by this, I have completed over 20 years of turning using chisels ground on a 5” bench grinder and if Sorby had not bought out the ProEdge I would have carried on in the same way. In the next part I will do my best to describe how to grind your chisels, you can read numerous books on the subject, you can watch other people do it, but the only satisfactory way is practice with an understanding of what you are trying to achieve, there is a bit more to it than just producing a razor edge.
THE ENJOYMENT OF WOODTURNING Part
4 Hopefully you now have your grinders set at a good working height, tool rests at the ready, all the wood dust and shavings removed from the grinding area and the grinding wheels dressed clean and true. Before we start on the actual grinding process it may help some of you to understand why have different grinding angles. Starting at 90 degrees we have an extremely strong cutting edge, but it will not cut anything as it will not get under the fibres of the timber, however the burr on the top face produced by the grinding makes an excellent shear scraping edge as you can make the bevel rub the work piece and have the burr do the cutting. Moving down to an 80 degree bevel, virtually the same as 90 except that because of the 10 degree slope on the bevel you can take a deeper cut, but again this is only a scraping cut. At the half way mark of 45 degrees we get a very strong and acceptable cutting edge making this a very good choice for bowl gouges due to the pounding they take. Moving down to 30 degrees we get a slightly weaker but very sharp cutting edge and because of the steeper bevel angle the tool becomes more manoeuvrable in tight situations making it excellent for spindle gouges. Moving on down further at a 15 degree bevel we get an exceptionally sharp cutting edge but a considerably weaker cutting edge, this need not concern you as generally this is a finishing tool which does not get the punishment that a bowl gouge gets. The one thing you need not do is go rushing around to measure any of these angles, something in the region of, is suitable and don’t be afraid to adjust them to suit your needs. For instance I have a bowl gouge ground at 60 degrees for those awkward cuts in the bottom of a deep bowl. A tip I was given many years ago by a well known professional, and still adopt today which is appropriate both to your turning as well as grinding, is, “make yourself connect with your machine” all this means is instead of gripping just the shaft and handle of your chisel, make sure you are contacting the tool rest. In photo 1 the fingers are locked under the tool rest and the thumb holds down the chisel against the tool rest. In photo 2 the index finger is pressing against the tool rest which also acts as a nice guide to cut in a straight line.
Photo 1
Photo 2 In part 1 I used the term “correctly ground” all that this means is we want one continuous bevel from the heel to the cutting edge as smooth as possible and the same side to side across the bevel. You may have a chisel that has got a scalpel sharp edge on it with 4 or 5 slightly different bevel angles under it. Of course when you try to use it to cut wood you find it is not doing what you hoped it would which is to leave a smooth semi polished surface on your work. The bevel is doing two things, 1. it acts like an artists or sign writers rest enabling them to paint very fine straight lines. In your case it is following immediately behind the cutting edge helping you turn straight or curved surfaces with out the ridges or bumps which you may have been experiencing. So if the bevel is not rubbing the work you have no rest and back come the bumps and ridges, to much bevel rubbing and you lose the cut all together and in the case of bowl gouges they will get very hot. The second thing it is burnishing the work as it is cuts, leaving that lovely smooth finish you have been dreaming of. Hopefully from the beginning of part 1 to now you see the benefits of the correct grade grinding wheel, too course and your bevel may be perfectly formed but the grinding grooves will be deep. If your tool rest is solid and at the correct angle there is no fear of it bouncing or moving and creating a second (or third ) bevel. If your grinding wheel is clean and well dressed it will grind over the full tool contact area rather than on top of the hills, making it grind quicker therefore less chance of you pressing harder to speed things up, creating excessive heat and loosing that fine delicate touch required for ultimate tool sharpening. All of this is applicable to both cutting and scraping tools, I’ll explain why later. Probably the first chisel and certainly in the cutting tools one of the easiest to grind is the roughing gouge, so let’s start with that one.
Photo 3 The angle of the tool rest needs setting to 45 degrees. If you don’t have a tool rest with pre-set stops as mentioned earlier you can make yourself a set of setting gauges from a bit of 6mm MDF once you have established a position resembling the angle you require simply mark the curvature of the wheel on to the MDF and cut it to the curve, see photo 3. Make one for each angle you require make sure you do mark the angle on the face. Depending on the type of tool rest you have, just rest the template on the top of the tool rest and adjust it up and down or in and out until there is no gap between the template, tool rest and wheel. The disadvantage of this system is that as the wheel gets smaller, the curved template no longer matches the wheel, but we are talking of months of use not hours, so it will certainly get you started. Make sure the gap between the tool rest and the face of the wheel is kept as close as possible.
Photo 4 Hold the chisel as in photo’s 4 and 5, the ferrule is quite a convenient place or the bulge near the start of the handle. Note in both photo’s the fingers are making contact in a safe place under the tool rest. In exactly the way you should be turning let the grinding wheel do the work you do not need to push the chisel hard against the wheel.
Photo 5 Hold the chisel with the centre of the flute facing upwards and the chisel straight in line with the centre of the wheel, gently ease the chisel towards the grinding wheel as soon as sparks appear, start to rotate the chisel to the left, all the way to the edge of the bevel, make sure you do not twist the chisel out of line, as soon as you get to the left hand side start to rotate to the right hand side. Continue this side to side rolling until the sparks start to travel down the flute of the gouge, you only need to move the chisel slowly if you have the correct grade wheel and it is clean it should not over heat the chisel. Lift the chisel clear of the grinder and carefully inspect the bevel. You should have one clean evenly ground bevel with very fine lines running at 90 degrees from the cutting edge down to the heel of the bevel. If the cutting edge has a small shiny spot or there is clearly no new bevel ground all the way top to bottom then just repeat the action. Principally that is all you need to know for grinding all your chisels, the only difference is in the way that you roll them or twist them to suit the shape and type of chisel being ground. Photo 4 shows a conventional 5” bench grinder using a tool rest which has pre-set angle stops. Photo 5 is showing the same chisel being sharpened on the Robert Sorby ProEdge, but the principal is the same for both machines. Once you feel a little more confident if you have a straight across (as opposed to finger nail) ground bowl or spindle gouge, try sharpening it in exactly the same way, just be cautious you do not roll it to far to the left or right otherwise you find the corner of your gouge slowly disappearing in a blaze of sparks. Photo 6 shows the tool rest with scribed lines on the front leg indicating the angles and you can just make out the corresponding locating holes in the side of the leg.
Photo 6 Depending on your type of tool rest you may be able to either purchase or make your own device to keep your gouges straight and square to the wheel while you concentrate on twisting it from side to side. Photo 7 shows the ProEdge grinding a shallow flute spindle gouge using a jig which comes as part of the plus kit. It is just a vee block with a locating lug on the bottom which sits in the groove on the tool rest, you can see a similar groove in my other grinding tool rest. I have utilised this block for another use which I will describe later.
Photo 7
Photo 8 You either love ‘em or hate ‘em, the skew chisel. Set your tool rest to about 15 degrees, hold it similar to the gouge we started with only this time move the handle to one side, in other words you are creating the “skew”, you must keep this angle throughout the grind much in the same way as you kept the gouge straight to the wheel, move the chisel towards the wheel as soon as sparks appear gently move it about 1/8th to a ¼” side to side on the face of the wheel but do watch that the handle follows you. The side angle is not important some like a steep long grind others even grind it virtually square. If this action of getting the handle to follow the steel bit is a problem (and don’t grab the handle, I’ll almost guarantee you will make matters worse) then don’t worry help is on the way. Photo 8 shows a skew chisel grinding jig (the black bit) as you can see it sits in the groove of the tool rest, it will slide from side to side but will not twist out of line. Hold one side of the chisel against the jig, grind one side, flip the chisel over to the other side and grind this side. From the point of view of using the chisel it is easier if you can grind both bevels to the same length, this keeps the cutting edge in the middle of the chisel and when you cut on either the left side or right side you do not have to alter the height of the chisel handle to compensate. It sounds complicated but I can assure you it is not. This is a fairly fool proof way of sharpening a skew chisel and it takes out most of the guess work. As with the roughing gouge you should end up with an even bevel with very fine lines running from the cutting edge to the heel of the bevel.
Photo 9 For simplicity in my workshop the photograph is taken using the ProEdge.
The thin blade parting tool, quite difficult to keep upright and square due to it’s thin section. In photo 10 the tool rest is at 45 degrees and I am using the side of the vee block to keep the chisel square and upright. Note once again I do not hold the handle, take a light grip as near the cutting edge as you can or are comfortable with and lightly let the grinder do it’s work. I’m afraid it does show the ProEdge again, but do exactly the same on the bench grinder the only difference is that the edge in contact with the belt will be contacting the wheel and it will take on the curvature of the wheel. That’s another reason why I have to photograph using the ProEdge because I have no more curved bevels.
Photo 10 I guess we are now on to the one you have all been waiting for. The fingernail ground gouge, it does have other various names but at the end of the day instead of grinding it straight across like the roughing gouge, the wings of the flute are ground back slightly or in some cases , a lot. You can grind this chisel on any grinder with just a flat top tool rest, assuming you want a 45 degree grind set the tool rest, present the chisel in the same way as for the roughing gouge, as soon as the sparks appear start to twist the chisel and swing the handle end through an arc sideways until the end of the bevel is reached then twist it and swing it all the way to the other side of the bevel. The difficulty is, only experience will tell you when you have rolled it and twisted it enough. Most of you I am sure are going to opt for a ready made fingernail profiling jig, be aware they are not cheap, look at as many types as you can. Ask around at the club who favours and uses what. Having said that Photo’s 11 and 12 are of a profile jig I made myself and have been using up until the last few weeks.
Photo 11
Photo 12 Virtually all the commercial fingernail jigs require the tip of the gouge to be set at a recommended distance from the jig clamp, most that I know of is 50mm, this distance coupled with setting the jig to the manufacturers instructions should give you a 45 degree grind, therefore a distance of 60mm will give you about a 30 degree grind, that’s basically how you alter the angle. From then on grinding is simple the jig controls the arc of swing and the angle to the wheel all you have to do is swing it the same distance to each side. For those wishing to get a bit more adventurous you can alter the profile of the bevel slightly, I found it useful for different flute depths, you can just make out in picture 12, the number 4 written on the ferrule, this is the setting I use on my commercial jig, (there are 6 notches on the clamp head, this gouge is ground set on number 4). The knack of this jig is grind the sides first do not grind the bottom of the “U” until both sides of the bevel are ground, keep checking the shape of the sides, you are looking for a very slight convex curve when you view them from the side and they should be equal in length and height, when you are happy with the sides just blend the bottom of the “U” in to the sides. You may think this is going to give a right old mixture of bevels, but it does n’t, when you have finished you should see an even bevel with the very fine lines running at 90 degrees from the cutting edge to the bevel heel. Photo’s 13 and 14 show the commercial jig in use ( it comes as part of the ProEdge plus kit). Note the hand grip again, the other 18 inches of the gouge and handle are well out of shot.
Photo 13
Photo 14 Another tip on offer is, particularly on bowl gouges when they are expected to run around the inside curve of a hollowed out bowl. I have already mentioned the bevel must rub behind the cutting edge. Pick up one of your existing bowl gouges and feel the edge right on the heel of the bevel, now although it will not cut you, as your sharpening improves this edge will also improve and you do not want it to, Photo’s 15 and 16 hopefully show what I do, after grinding the bevel I hold the chisel clear of the tool rest and free hand roll the heel of the bevel very lightly against the grinding wheel, just enough to remove any sharp edge. I then put the heel of the bevel only on my burnishing wheel and polish it for a few seconds, you can use an oil stone, diamond or even wet and dry paper. You can see the polished line at the tip of the pencil in each photograph.
Photo 15
Photo 16 What’s left? Scrapers and little bits. Lets start with scrapers. These are probably the easiest of all chisels to sharpen, choose your preferred grind angle 45 degrees for aggressive cutting, working up to 80 degrees for less aggression. 90 degrees give a good easy to use shear scraper. Set your tool rest angle hold the chisel flat and grind a straight across or curved contour. Photo 17 shows a massive 50mm by 10mm thick scraper being sharpened on the ProEdge. Jumping back to page one I said I would come back to the grind of scrapers. They do not rely on a sharp cutting edge like a gouge, instead they use the burr created by the sharpening process, just click your thumb nail over the ground edge of any chisel and you will feel it. Now the finer the grinding wheel the more upright jagged bits you will have on your chisel, which is exactly what you need, so don’t just think of a scraper as a chunk of steel you can shove against and old grinding wheel, sharpen it much as you would your most favoured bowl gouge and it will reward you with the most pleasant cutting action. In furniture making terms this burr is know as a ticketed edge when it is deliberately applied using a very hard and highly polished piece of steel slid along the cutting edge. So the burr can be replaced either by a few rubs with a diamond or oil stone. I usually find it quicker and easier just to touch against the grinder for about 2 seconds, virtually no material is lost from your chisel if you have all that has been discussed above.
Photo 17 If you try to use a wheel to course the very fine lines I have mentioned that appear on the bevel are in fact minute grooves become deep grooves so you therefore end up with less of a straight line of burr which the abrasive revolving wood will quickly remove. I have found that it pays every now and then to polish the top of the scraper with an oil stone or diamond, which gives you some new steel to play with and forms a stronger burr. I’m sure a number of you will have a collection of high speed steel teardrop tips and swivel tips. On a standard tool rest and grinder these are a nightmare to sharpen and pose a danger to your fingers or even worse loosing your grip of the little devils and having them jam between the tool rest and the grinding wheel. There is a well thought out inexpensive little gizmo available from Stiles and Bates (I believe Robert Sorby may do it also) which will hold the teardrop tips on one end and the half round swivel tip on the other end (see photo 18)
Photo 18
To use, fit the tip in the holder, set your tool rest to the desired angle, place the holder flat on the tool rest and move it to create the desired shape, you will have to slacken the tip mounting screw and rotate the tip as you proceed. It makes the sharpening of these awkward little bits a very safe and easy process. Photo’s 19 and 20 show a teardrop and swivel tip being sharpened.
Photo 19
Photo 20 Finally if you find all the angles a bit confusing and you do invest in the Robert Sorby ProEdge sharpening system, it comes with a nifty little reminder plate attached to the front of the machine showing the tool rest locating hole pattern, with the grind angle it will produce and a description of the types of woodworking tools that can be sharpened at each angle. Alternatively there are several sources from where you can purchase plastic encapsulated wall charts showing the grind angles for each type of woodturning chisel.
Photo 21 The last point to mention which undoubtedly may well be a contentious one is :- To hone or not to hone.? I spoke about the burr produced by the grinding process leaving a burr suitable for scraping. That same burr is also left on your cutting chisels. Some professional turners advocate removing the burr with a diamond or slip stone, others say leave it alone because as soon as the revolving wood touches it, it will be removed anyway. I use a mixture of both, on a bit of Elm, the burr left on the bowl gouge is quite helpful. On a piece of Pine or tight grained timber such as Sycamore I find it a benefit to remove the burr using a slip stone with a soapy water mixture (you can see the spray bottle in some of the photo’s) on the flute of the gouge and a little rectangular Arkansas stone on the bevel side. Perhaps some of you would like try both and post your comments on the members page. I hope this article has provided you with some food for thought or practical help to get your chisels really sharp and gain even more enjoyment from your time spent creating shavings (no more dust).
Mike O’Connor mike.ant@virgin.net W&DWT member Back to All
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