Note: The critical insight that Benton had, which was copied in later cutter grinders such as (at least) some of the Gortons, was that the for work of the precision required for matrix engraving the spindle must be removed from the engraving machine with the cutter and cutter-regrinding done with them as a unit.
Why is this important? A spindle has nice big reference surfaces which allow it to be removed and replaced in a machine in exactly the same position. A cutter, though, has a tiny sharp point, and it is very difficult to get the same depth of cut after resharpening a cutter if you have removed it from the spindle. But if you take the entire spindle out and put the whole spindle in the cutter grinder, the spindle will have the same relationship to the grinding wheel every time. You can loosen up the cutter in the collet, move it down a bit to get fresh material to grind, and still grind it so that the cutter+spindle as a whole are identical to the last time you did this. Benton discovered in the 19th century that this is the only way to ensure that a resharpened cutter will be indentical to its previous self in both form and depth. (Actually, Benton went one step further and preserved the relationship not between the spindle and the grinding wheel, but between the spindle and a diamond dressing point redressing the grinding wheel at each cut. Benton was like that.) Still, Rimmer worked without such a setup, and if I ever get to the point where I produce work half as good as his, I'll be very happy indeed.
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