Hi Richard,

I think the "black square block" is nothing more than some type of carborundum stone. Cecile's method is tried and true. He did a great job of it!!!

I've used the method he shared and it's a great one if all you have is the big stone itself spinning and want a less expensive "hand method"of truing the spinning stone. This is the "tradtional method" for truing sharpening stones of this type. I'm not familiar with any other methods other that a "bushing wheel" but that is a tedious method in my experience and view of it.

I find the diamond stone works so fast that truing even a badly out of true stone goes really fast. I've never had one take more than about 35 minutes for the worst of them...most in lest the 10 minutes of work.

Blessings,

j