I think that hollow grinds are done on a wheel. I am not a machinist or knife maker. Some of the knife making stuff I saw at blade had different wheels. I think they are used in hollow grinds, but I'm not sure. I think a flat platen would be used on the ricasso to smooth it out but I'm not sure. All I know is that it did not take me long to learn how to sharpen machetes on my belt sander and things just sort of progressed from there. I think they are esier and safer than bench grinders that many people have.