Sharpening Carving Gouges
I had experience as a carver of furniture parts, but when I joined Doug Bernhardt a few years back for a six-month stint in his sign carving shop, I quickly learned a lot more about sharpening. The tool should always shear its way into the wood, and not want to come up out of the cut. Only moderate force is required with a sharp gouge.
When you buy a gouge, it often comes with an edge on it, but most often it does not have an inner bevel. Remember, every edge has two sides to it, so that inner bevel is just as important as the main bevel on the outside of the tool. To create the inner bevel, we use a fine Arkansas stone, called a slip stone. These stones are teardrop shaped in cross section, measuring about 4-1/2″ long x 1-3/4″ wide, with a 3/16″ radius curved edge on the wide side of the teardrop. It is the large radius that we use to shape and tune the inner bevel of the gouge.
A Curved Stone
In order to work the inner portion of a curved gouge a teardrop shaped stone, called a slip-stone, is used. Its two sides are radiused, allowing you to choose between a tight or medium curve, depending on the tool you’re sharpening.
When using a felt wheel to hone a gouge, it must rotate away from the user.
Shaping the Gouge
Lee Valley makes a sander/grinder, to which the user attaches a small motor. It makes sharpening the curved backs of gouges easier.
Select a stone
As with all tool sharpening, stone choice is personal. When I first learned to carve, we were taught to use Norton oil stones – they still work fine today, some 20 years later. Lee Valley sells water slip stones that will do the job just as well. Coarse water stones for shaping are rated at 1000x, finer stones for tuning your inner bevel come in at 4000x and for that final keen edge, at 8000x. Doug prefers the natural white Arkansas stone, so there you have it – they all work, choose the weapon that you prefer.
Doug uses the Lee Valley Sander/Grinder in his shop to quickly grind the outer bevel on all of his gouges. He uses three different belts on this vertical 1″ wide belt grinder. He uses 120 grit for shaping, and then 15 and 20 micron belts for finishing. Gouges can also be shaped on the broad side of a slip stone, but it takes considerably longer to do. Alternately, to shape an outer bevel on a bench stone, place the existing bevel flat on the stone (the handle of the gouge is to your right, at 90º to the length of the bench stone), and then raise the tool handle ever so slightly to ensure the leading edge of the bevel is in contact with the stone. Sweep the tool along the length of the stone, while rotating the gouge to expose the entire edge to the stone. This works relatively well, but it requires a fine touch to keep the tool rotating evenly as you traverse the length of the bench stone. Having used both methods, I recommend heading to Lee Valley for their relatively inexpensive Sander/Grinder at $85, to which you will need to add a 1/8 HP motor.
After coarse shaping and fine grinding on the Sander/Grinder or bench stone, polish the outer bevel on a buffing wheel. The wheel is attached to a motorized bench-type grinder, with one important exception – the rotation must be away from you. The wheels are commonly made of hard felt, and will cut very well when charged with honing compound. Honing compound is chromium oxide suspended in a bar of waxy material. Polishing is rather quick, requiring only 30 seconds after a fresh grind to achieve a glistening surface. If the gouge has a conservative sweep, the inside bevel can be quickly touched up by turning the tool over, and placing the inner bevel at 45º to the edge of the felt wheel. For gouges with a tight radius, you may wish to buy a felt wheel shaped into a concave leading edge – this gives you two surfaces to work on the inner bevel with.
For the budget conscious, similar stropping can be done using a leather strop. A strop is a hardwood “paddleshaped” tool about 16″ long x 2″ wide x 1″ thick. You can make your own strop by visiting a leather shop and getting a thick cut-off of leather about 10″ x 2″ x 1/8″ or slightly thicker. Simply glue the leather to the hardwood paddle, smooth side out, and then charge it with 0.5 micron honing compound. Again, the action must be a dragging action down the length of the strop. Keep your gouge at an angle just slightly more that the primary grind on the outer bevel to ensure the leading edge is being conditioned. If you are using the manual strop, then simply clean up your inner bevel using a fine slip stone.