Copyright© 2011-2015
Web Design and Hosting by JHJ
Doc Green’s Woodturning Site
Free-Hand Sharpening

This is another topic that brings strong opinions to the front in regard to sharpening turning tools at a grinder.  Most use a jig of some sort to hold the tool and argue that the jig removes the guesswork and guarantees repeatability.  A few of us get results good enough to satisfy ourselves without using a jig and argue that a jig is a waste of money and time.  

The truth is, I began sharpening free hand before I knew there was any other way to do it.  By the time I learned about jigs for sharpening lathe tools, I had already formed the opinion that I could do it free hand and could see no reason to change what I was doing.  

So, here is my method of sharpening bowl and spindle gouges without the use of a jig.  

The heart of my setup is a slow-speed grinder (1750 RPM) equipped with a 120-grit aluminum oxide and a 120-grit diamond wheel.  At the front of each wheel is a platform on which I rest the hand being used to touch the tool to the wheel.  A small fluorescent desk lamp provides illumination.      

To be in control of the sharpening process, you must be able to see the line of contact between the bevel of the tool and the wheel.  This is not possible if the tool is applied with the body more or less in line with the wheel.  

I begin with the handle of the tool very nearly horizontal with the flute pointing directly away from the (120 grit) wheel.  This starts the grinding at the front center portion of the bevel.  My left hand is placed on the platform and grips the tool an inch or so back from the tip.  It steadies the tip and applies the force that presses the tool against the wheel.  

At the same time, my right hand lightly grips the end of the handle and is used to aim the tool so that the bevel is always parallel to the surface of the wheel.  Once contact is made and the grinding begins, my right hand raises and rotates the handle in such a manner that the bevel is rolled onto the grinding surface.  During this phase, the bevel seems to “seat” against the wheel so that aiming the tool is not hard to do.  This will sharpen the right half of the tip of the tool.

Next, I switch the tool handle to the other side.  My right hand now applies the bevel to the wheel while my left hand aims and rotates the tool handle.  Again, the bevel is rolled onto the grinding surface.

After both sides are ground, I look at the front center of the bevel to see that the curve of the bevel is smooth where I started the left- and right-hand passes.  If there is any discernable line, or in the worst case a ridge, I will roll that portion of the bevel against the wheel to smooth it out, most likely moving over to the diamond wheel to do it.

This is a gentle process; few sparks are produced because of the very light pressure used to press the tool against the wheel. Further, because I can see the line of contact between the tool and the wheel, I can avoid the common problem of getting multiple bevels by simply keeping the bevel parallel to the wheel.   

It goes without saying that for this to work, you must know the type of grind you are trying to achieve.  The grind I prefer on a bowl gauge is one where the bevel wraps around the shank of the tool a small amount.  For spindle gouges, I go with the traditional fingernail grind.  

Then and now.  Now that I have considerable experience with free-hand sharpening, I’m more likely to approach the wheel with the tool at an angle of 30 - 45º as opposed to having it almost horizontal as described above.  I touch the heel of the bevel to the wheel first, and then tilt the bevel toward the wheel until I feel it make full contact.  Then a quick roll to grind out on the wing, and I’m done – except for doing the other side, of course.

As I’m grinding out on the wing, I look for an occasional spark to come across the top of the cutting edge.  This indicates that I’m grinding the bevel all the way to the edge.  Even when there are no sparks (due to an extremely light touch), I can see a small change in reflected light right at the cutting edge.  

Touching the heel of the bevel first usually results in a slight rounding of the bevel near the heel, but this is not a bad thing. In fact, many turners suggest rounding the heel in order to avoid having the otherwise sharp corner create compression lines as the gouge is used to cut a concave curve on the inside of a bowl.

All this takes place as one fluid, smooth motion.  I don’t dwell at the heel as I’m seating the bevel.  And yes, every now and then I’ll screw up and get a multiple bevel.  In that case, I simply fix it by taking another pass a bit more deliberately.  

If my intent is to change the angle of the bevel, I begin with the tool handle horizontal as described initially.  Once the desired angle is established at the tip, I then roll the tool to wrap the bevel out onto the wings.

Using the diamond wheel.  I use it more as a hone than a grinder.  After almost three years of use, its initial 120-grit surface is now probably closer to 180, but it still works fine to polish a bevel or to touch up an edge on one of my smaller gouges.  I do not use it on the gouges I use for roughing cuts because I figure the benefit is not worth the wear and tear on the wheel.

A characteristic of the cutting action is that it doesn’t produce sparks.  In fact, very little heat is produced so that the tool stays cool.  Another feature is that the wheel is not grabby at all.  This and the absence of heat allows me to sharpen small cutters, hand held, that I would not dare touch to a 120-grit stone.  The cutters typically are for a coring system or hollowing tools, some of which are carbide.

One application where the diamond wheel really excels is in polishing the bevel of a scraper prior to burnishing to form a burr. The surface left on the bevel by the diamond wheel is far smoother than what is left by a 120-grit stone, and this translates directly to the production of a more uniform burr.  Such a burr will be stronger and will last much longer than a burr produced by grinding without polishing the bevel or burnishing.  (See the article on scrapers.)

Sharpening a spindle roughing gouge.  The traditional grind has the same bevel angle of about 45º all the way around the cylindrical body.  This makes it particularly easy to sharpen. Simply seat the bevel as described above and then rotate the tool.  If the handle is dropped about 15º below horizontal, you can watch for sparks to come across the top of the bevel. This will serve as an indication that you’re grinding all the way to the cutting edge.

Parting tools, skews, and scrapers.  Sharpening methods for these tools are included in the articles addressed to the particular tools.  See the article index.