If a gouge is being traversed around a concave surface such as the inside of a bowl, and the gouge has a hollow-ground or hollow-ground-and-flat-honed bevel the bevel heel is likely to be used as a fulcrum. This will exert high pressures which will leave paler rings of crushed cells clearly visible on the wood’s surface. The obvious way to avoid this damage is to use gouges with a convex bevel.

In his 1995 edition of The Practice of Woodturning Mike showed how easy it is to grind convex bevels in the concave periphery of an aluminium-oxide grinding wheel. This advice was repeated on page 50 of The Fundamentals of Woodturning.

Recently, grinding two- or three-facet bevels has been promoted for this same purpose. This lessens but does prevent crushing damage, and it then takes far longer to grind the multi-facetted bevels. However, you don’t have to dedicate a grinding wheel to grinding convex bevels.

Figures 1 to 6 explain how to produce convex bevels. Give them a try. You’ll wonder why they haven’t caught on.

Figure 1   This image of a grinding wheel with a concave periphery was published in Germany in 1905 with the warning that you shouldn’t allow your grinding wheels to get into this state. However such a periphery does enable convex bevels to be readily ground.

Figure 2   About to dress the concave periphery of an aluminium grinding wheel with a dressing stick. The diameter of the wood gauge is 35 mm.

Figure 3   If the gouge is presented radially, the bevel has the same convexity as the wooden gauge in figure 2

Figure 4   If the gouge is tilted up, the bevel convexity is reduced

Figure 5   The concave periphery can be used to hollow-grind bevels in the usual way

Figure 6   The gouge with a convex bevel I use to rough-hollow bowls. To finish-turn bowl insides I use three different gouges, each ground square-across with a convex bevel but with a different sharpening angle