Debate: Grinding turning chisels To test the response from forums on the grinding of gouges and skews we asked a group of professional turners how they sharpen their tools. Here is a sample of their response. If you would like to add your comments, email us with your thoughts and we’ll add them to the debate. mailto:advice@britishwoodworking.com?subject=Hollow%20or%20flat?shapeimage_2_link_0
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Terry Atkinson, Scotland: Hollow, on balance “When you have been turning for some time, I suppose you cut the wood without really thinking. But from first principles you were taught to rest the back of the tool on the spinning workpiece and raise the handle until the tool starts to cut. If the tool is hollow ground then it would fit neatly with the cylinder and the back of the tool can support itself against the workpiece, giving a very secure cut.” Tom Pockley, Kent: Largely hollow “My sharpening techniques may be coloured by the fact that I teach woodturning and I try to use a system that gives tool shapes that are simple to use and also simple to replicate without the use of expensive jigs. When planing a cylinder between centres [with a skew] a hollow grind is helpful. I am making knitting needles, 3mm in diameter, at the moment and it is interesting, when trying to apply the edge subtly, to see how a hollow grind can be used to ensure that the cut is delicate and there are fewer excessively strong cuts. A beginner trying to hone a flat bevel seems more often to turn the edge over so that the tool is not sharp.” Bob Chapman, Yorks: Keep it personal! “I think that the parameters for grinding tools are actually quite wide, and within these parameters individuals will gradually find what suits them best. The secret is to remain open to new ideas, keep trying the ones that appeal to you, and maintain a policy of continuous improvement. I think there is quite a bit of well-meant twaddle talked about grinding angles and bevels and so on. What many of these speakers disregard is the role the turner has to play. Of course I accept that the tool has to be used correctly in order to cut well, but they seem to start from the premise that all bowl gouges or skews or scrapers should be ground the same way and that all turners should then learn to use them in the same way. Tools are personal, everyone knows that. It’s because the turner and the tool in his [or her] hand become a unit. It’s that unit which does good or bad work, and if you change either of the two parts the work may suffer.” Phil Irons, Warks: Make it sharp! “I think that the most important thing is not how the sharpening is achieved by that the result is sharp tools.” Gregory Moreton, Surrey: Hollow “Without hesitation it is certainly best to hollow turning tools. A hollow grind will take the point of contact on the bevel against the wood further from the cutting edge. This in turn creates a more efficient lever, leading to better control and hopefully a more accurate cut.” Reg Sherwin, Worcs: Hollow “I favour the hollow grind. Flat is often actually slightly convex, especially if produced on a linisher, as the abrasive yields a little to the downwards pressure from the tool, and then comes back up again as it travels past the cutting edge. A tool sharpened on a leather strop takes the same profile, albeit microscopic. “I find that on planing cuts the two small contact areas of a hollow ground bevel (the front and the back) create less drag on the surface of the wood, making the tool far easier to ‘feel’ during cuts. For speed of sharpening I hone tools between grinds, maintaining two points of contact (the front and the back of the bevel) with a dry carborundum stone. Depending upon the tool and the timber being worked I may hone up to five or six times between grinds. “Many, probably most, of my fellow professionals use the tool straight off the wheel and into the wood. I prefer to get rid of the burr, which is the old edge, with a de-burrer, which is a piece of scrap wood turned to a rounded point at one end.” (Reg now has an eight-disc DVD set which can be found at www.ktmp.co.uk. We will be reviewing it soon.) Les Thorne, Hampshire: Hollow grind “I nearly always sharpen my tools on a round stone for a hollow grind, but I do often remove the heel of the tool to create a secondary or micro bevel, therefore creating a smaller hollow ground effect. It is a way of making a larger tool cut like a smaller tool with the strength of the bigger one. This only applies to gouges; on the skew I just roll the tool up the wheel to remove the harshness of the heel.” Duncan Askew, Cornwall: Hollow grind “As a professional turner, I always hollow grind my chisels and gouges, straight from the pink (not ruby) wheel. I do not hone them afterwards. But here’s a tip that will help turners who have difficultly sharpening chisels. Make sure that the drive shaft of your grinder is at the exact same height as the shaft of your lathe. Try it, it works (trust me I’m a turner).” Barry Badger, Middlesex: Hollow grind “To hone a turning tool is a waste of time. The bark holds so much rubbish that the honed edge last no time at all. Better to come straight from the grinder and regrind often. If you use a sharpening wheel it is inevitable that you will eventually form a hollow grind, with no ill effects in my experience, so my vote is for the hollow grind.” David Bates, Kent: Flat or hollow “With the jigs and guides now available it is easy to grind a truly flat bevel and this is probably easier to keep in good contact with the wood, especially with skew chisels. There is also the advantage of no bevel heel to mark the work. “Any rounding of a flat bevel will mean that presenting the cutting edge with the bevel rubbing is more difficult. The hollow bevel is recommended for beginners to avoid the risk of sharpening with a flat bevel. “I switched to flat bevels on skews for our courses and am sure they are easier to use. Since the introduction of the Sorby ProEdge I have ground a range of tools in this way, and find them to be superb. It’s all to do with sharpening a truly flat bevel.” Alan Truman, Nottinghamshire: Flat “I am of the belief that a flat bevel on a skew chisel is the best option by virtue of the fact that the flat of the chisel is resting on the work and thus giving the chisel optimum support. The effect is similar to the cabinetmaker’s paring chisel, which is always used with the flat of the blade in contact with the timber.”http://www.ktmp.co.ukshapeimage_4_link_0
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Grinding turning tools Les Thorne adds a secondary bevel to his turning gouges. This, he says, makes a large gouge feel like it’s cutting like a smaller gouge. Tell us what you think of this. The UK’s No.1 Woodworking Magazine
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