Honing Woodturning Tools
By Alan Lacer
Rude Osolnik did it, so did Bob Stocksdale and Del Stubbs, Jerry Glaser recommends it, Peter Child and Frank Pain in their turning books advocate for it, George Hatfield in Australia teaches it, Japanese turners do it religiously. However, I think it is safe to say that those who hone their tools are in the minority of woodturners these days-and I'm not sure why this is the case.
Let's begin with some basic sharpening terms as they relate to woodturning tools: profiling, producing an edge on the profile, and honing; all of these at times are used to describe the process of sharpening. Profiling or shaping the tool involves the form you or the manufacturer imposes upon the steel which includes bevel angles. Next, there is the attempt to put a sharp edge onto that shape-to me this is closer to how most people would use the term "sharpen." Honing (or whetting) simply refers to the refinement and/or maintenance of a sharpened edge. Most often in woodturning this relates to gouges, skew chisels, parting tools, and ring/hook tools (scrapers are in a special category, but I still use my honing equipment-but more on that later). To me these concepts flow in their importance in the same order: it does no good to sharpen (to put an edge on) a poorly profiled tool and I can't hone a edge that is not to some extent reasonably sharp and properly ground.
I should clear up something before we have gone too far: hand honing does not replace the need for power equipment. Woodturning tools are in a special category as hand woodworking tools go. We generally make use of power grinding equipment to do the profiling and edging process-I know of no professional woodturners who do the entire process by hand alone. This is due in large part to the new steels: high speed and high wear resistance tools now dominate the serious turning tool market. These tools are virtually impossible to shape and sharpen by hand alone. Thus, turners use powered belts or discs, or what is most common, a power grinding wheel. Add to this that the majority of turning tools need some modification, sometimes extensive modification, you find that a piece of grinding machinery is necessary to be a woodturner these days.
So why do so few turners take their tools to the last phase, that of honing? There are several reasons. First, the tools are considerably tougher these days and many of the hand honing stones just don't work very well or not at all. I have in mind natural stones like Arkansas and Washita and man-made stones like Japanese water stones and the gray carborundum stones. All require lubrication (oil or water) and may require an inordinate amount of time to achieve satisfactory results with today's tool steels. Also, some turners feel it is simpler or quicker to return to the grinder when an edge needs addressing. A few maintain that they get the same quality of edge off the grinder as they would from honing-and that any extra refinement is a waste of time.
So why hone an edge?
I see a couple of reasons. The first one is to achieve a keener edge when necessary-and it is not required for every tool nor in every situation. It is usually not necessary for a scraping tool where heavy stock removal is going to occur as we use the burr off the grinder. Also, on a cutting tool (skew, gouge, hook/ring tool, parting) where one intends to perform rough cutting operations, I find no reason to refine the edge just off the grinder. However, for clean cutting of end-grain, softer woods or just difficult wood, especially that last pass which will determine the degree of sanding, I will refine the edge through honing. I find that honing for 30 to 45 seconds can easily make the difference between one or two grits in the sanding process. A tool like the skew chisel screams to have a very, very keen edge for purposes of both control and clean cutting.
Secondly, I hone to keep a sharpened edge sharp. This allows me to keep turning without running back to a grinder to achieve a keen edge, thereby simplifying the turning process. When I started turning one of the few turning books available was Frank Pain 's The Practical Woodturner. In that book he stated:
"At the works where we could turn 2 gross of chair legs a day, probably four or five tools would be used and they would be ground once a day. Some work of course might call for more frequent grinding, whereas for some beech jobs they might last for days."
I read this with complete disbelief early on as a woodturner. I was returning to the grinder, it seemed, every 10 or 15 minutes, not once per day. And to top it off, in Pain's day the tools were high carbon steel, not some high-tech specialty steel! Some of my problems were clearly due to presenting a cutting tool at a scraping angle and thus shortening its life as a sharp tool, and partly due to inconsistent grinding, failure to achieve a consistently keen edge all along the cutting edge. But as one reads on in Pain's book he describes the process of honing the edge to maintain the keenness from the original sharpening process. So, that's how they did one grinding per day or over several days. Just like the old time barber honing or stropping their razor, the process was not to take a dull tool and make it sharp, but to refine and keep the edge sharp. This is why many of us hone while turning-to keep the keenness within a range of sharpness-I call it the "sweet zone" that allows me to keep working efficiently, cutting cleanly when necessary, with more control or to reduce sanding time (see diagram1). Cutting wood tends, of course, to move the edge to the right on the scale-with even the best of steels. When the edge is honable it pushes it to the left on that same scale
So, we should ask this question: Can you get an edge "too sharp?" Maybe the phrase should be, "too refined" an edge. A woodturner seldom needs the polished edges so sought after by carvers, handplane users, etc. due to the fact that we are cutting and removing wood at a rate most hand workers would have to spend hours or days to equal. At 1000 rpm on 3" diameter stock, the turner is potentially cutting 785 feet per minute. So, no, we won't fuss and push to the same level as the carver or cabinet maker with a paring chisel, but we do need a sharp edge to work both efficiently, safely, and not to have a mess of things when we turn off the lathe.
Honing Process For Skews, Gouges, Parting Tools And Ring/Hook Tools
As I have already said, shaping the tool and grinding properly are fundamental and are more critical than honing. Simply stated, I can't hone a tool that has been poorly ground and it is a complete waste of time to attempt honing unless these other steps have been performed well.
Assuming you have acquired a serviceable shape for the task at hand, grind the tool to a level where honing will both be possible and beneficial to the turning process. My personal guidelines for achieving this during the grinding process are these: a slight hollow-ground bevel and minimal facets-especially facets above the concave face of the hollow-ground bevel.
Why a hollow-ground, why not a flat or convex bevel? The only reason I see for the hollow-ground bevel is that it provides me with a built-in honing guide-as long as I have a two point contact surface, I can better feel the honing process (see diagram to the left). However, there must be a balance between too much and too little hollow grinding. I prefer the concave profile produced from a 6" to 8" diameter wheel; much less than that in diameter produces such a deep hollow that it may indeed weaken the edge; much greater produces almost no hollow-and therefore no benefit.
Producing a ground surface with minimal facets is essential. If there are multi-facets that arise above the line from the heel of the bevel to the cutting edge, then the only thing I will be honing are these high points and I will do nothing for refining or improving my edge. Just as in grinding the edge, I try to train myself not to hone the edge; I focus on the bevel and not the edge. If I focus on the edge, invariably, I will grind a short bevel just behind the cutting edge or, when honing, I will tend to dub or rollover the edge.
When we talk of honing there are usually two ways to understand it: hand honing and power honing. In hand honing one may make use of a stone, rubberized abrasive or piece of leather. Personally, and more common with the turners I have known who are honers, would be the stone-natural or man-made.
Tips to Select the Proper Stone
First, select a suitable stone. With contemporary tool steels the best luck I have had is with the man-made India slipstone in a medium grit and, of course, with diamond (fine and super fine). Technically the India stone is an oilstone, but I tend to use them dry and regularly clean the build-up of metal particles with WD-40. The India slip is fine for removing burrs from the inside of gouges and the flat side functions to hone the outside bevel of gouges. However, in a short time the flat side becomes concave and does not work so well for skews and parting tools. It is still okay for gouges, but not for the flat tools. For these, and sometimes the outside bevel of gouges and ring/hook type tools, I definitely prefer a diamond coated stone (usually diamond applied to a mild steel plate). For gouge flutes, the diamond-tapered rod or cone works quite well. Be careful with diamond coated systems, as not all are of the same quality. Cheaper versions often use fewer diamond particles and a type of industrial diamond that breaks down quickly, that really is a case of "you get what you pay for."
Develop Your Honing Technique
Next, determine your honing technique. I have seen many
I personally prefer to get very solid and hold the tool against my body-and again move the stone along the tool (see Tool Holding:). As for the actually honing process, I always begin at the heel of the ground bevel. Next, I start the action of honing with a back and forth motion from the heel towards the edge. When I feel the bevel adequately I lower this honing action towards the cutting edge until I feel that second point of contact. Always maintain this two-point contact, i.e. the hone bridges the slight concave region between the heel of the bevel and the area just below the cutting edge. Remember, you are honing the bevel and not the edge. If the tool is a gouge or hook/ring type of tool, I finish by honing the inside flute. The nicety of this last operation, at least with gouges, is that I have another built in honing guide: hold the slipstone or rounded rod flat in the flute-again, not touching the edge itself, but focusing on the two planes that trap the area we call the edge.
Does all of this take too long? If it does you're doing something wrong. For me honing is like a cold swim, quickly in and quickly out. In truth the honing process should be under 45 seconds in most situations-even with a large tool like a roughing gouge. If it is taking longer to see any improvement then one of two things are occurring: either I have a poor honing technique or the edge is past the point of being honable-it's back to the grinder.
Make Your Own MDF Wheeel
There is another approach that can be used in combination with hand honing or as a substitute for it: power honing. This is most often done with a motorized wheel or even mounted on an arbor on the lathe. The wheel can be felt, stitched cotton, leather, cardboard, rubberized abrasive, or even wood, plywood or MDF. For turning tools I tend to stay away from the softer surfaces like felt, leather, cloth and even cardboard-with our heavy weight tools and a bit too much pressure I run the risk of rolling over my edge. My first choice is also a frugal one: the medium density fiberboard (MDF) charged with a buffing compound that will cut high speed steel.
The MDF wheel can be glued up for width from scraps of this material-find a cabinet shop nearby, and they probably of dumpsters of cutoffs. I make the wheel diameter approximately the size of the grinding wheels I use so that the hollow ground area is a bit simpler to feel. Since I grind on an 8" wheel grinder, my MDF flat wheel are 7" to 71/2" in diameter and 1 1/2" wide (two pieces of 3/4" glued together). The wheel is mounted on an arbor and turned on the lathe to a round, flat disc.
The disc can be mounted any number of ways: arbor mounted directly onto a 1/4 or 1/3 hp 1725 motor, pillow block and shaft, or left on an arbor that mounts on the lathe (best if not on the lathe you will be working on, as it is not practical to remove work from the lathe to hone-remember, it is quick operation.
Whatever the system, set it up to hone with the wheel going away from you. I find that high speed is not necessary-I prefer the speed to be rather low, 600-1000rpm is adequate.
I charge the wheel with buffing compound rated for stainless steel (I have had great luck with the Dico brand). I have also used Zam, a green honing compound that gave similar results. Whatever you use, look for the honing compound turning black as you hone; this indicates that you are removing some metal and not simply polishing the surface.
The actual technique is straightforward and similar to hand honing. With the wheel moving away from you, charge it with honing compound, place the heel of the bevel towards the top of the wheel-cutting edge up (see Power Honing Skew:).
Gently lower the bevel onto the wheel until you have that same two point or full contact of the bevel on the wheel. Again, do not focus on the edge, as you will round it over in a nano second. When I see the blackened mud trail just coming under the edge, I stop. This again is a very quick process-if a little is good more is great is the wrong approach.
Personally, the only tool I routinely power hone is the skew chisel, as its long edge benefits from this treatment. Occasionally I will do this for the outside bevel of gouges when I have a particularly difficult piece of wood. In that case I either use the slipstone to hone the inside flute, or I have MDF wheels with turned beads that fit the inside flute of my gouges to refine that side of the gouge.
Other Uses Of Honing Equipment
I find several areas of tool refinement that respond well to honing tools.
One is with scrapers: to flatten or refine the top of the scraping tool, removing milling marks, and removing the burr-either a worn burr or the burr off of the grinder.
Why flatten the top? The topside of the tool, the unground side, becomes one of the planes forming the edge. If it is uneven, pitted, or textured with milling marks from the manufacturing process, you will produce an uneven burr or edge which makes a difference for fine work with these tools.
If the top edge is severely afflicted with pits and milling marks, you may need to resort to a belt sander/grinder with a flat platen to clean up the surface. Following that, or if the tool is in reasonably good condition, simply hone that surface with a flat hone (again diamond is my first choice). Most of this is tool refinement.
But in actual use I also use a flat stone (my India slip or the flat diamond stone) to do two operations: remove the old burr before pulling up a new one or for removing the heavy burr that is almost always produced by the grinder. I remove the heavy burr if my objective is to use the scraper as a finishing tool and not for heavy stock removal. Just a few passes with the stone held flat on the top of the scraper removes the old burr. Next, I use either a cabinet maker's burnisher to raise a fresh burr to my liking, or more commonly for me, I will use the flat face of the India slip stone to act as a burnisher and raise the burr-it works well to produce a light burr for finishing work.Personally I use the scraper much in the same way the cabinetmaker does with their scraper: with a burr 90% of the time, and most often as a finishing tool.
There is another place for the power hone: to remove the milling marks from the inside of a gouge's flute. Today just about all bowl and detail gouges are ground from round bars of high-speed steel. This has been a wonderful development in many ways, but it also has one drawback: virtually all of these tools show signs of the milling process, some worse than others, that again forms one of the faces that produces a sharp edge. By removing or reducing these milling marks I find you have a superior tool in edge quality.
By shaping the MDF into convex bead forms, I can remove or greatly reduce those milling marks (see Milling Marks:). I normally turn the beads from 3/4" MDF, making several different widths for the beads (see Buffing out the flute of gouge:). Once again, work with the wheel going away from you, charge with buffing compound, work on top of the wheel, and only concentrate on the last 1 inch or so of the tool-do it again when you have worn the tool down to the area you have polished out. I find that some of the specialty high speed tools require considerably more time and effort and possibly a more aggressive buffing compound to begin the process (such as the gray or emery compound).
Do we need to hone? I find it indispensable and essential to good turning, but knowing it is not for all situations or even all tool applications. In some woods, especially wood on the dry side, or where I am dealing with ornery end-grain, it appears to be a real asset. In getting a fine edge I preserve crisp work, have more control, keep the piece round by reducing the amount of sanding, and streamline my sanding process-both in time and grit size. And if you are somewhat frugal, you greatly extend the life of the tool by keeping it sharp, not by running to the grinder every little bit, but simply by keeping it sharp with a hone. Experiment, develop your technique, then judge for yourself the merits of honing.
A similar version of this article appeared in American Woodturner in the Spring 2003 edition.