Lesson #16: Making sharpening stones for curved chisels ... (part one)
(contributed by David Bull)
It's not difficult to find suitable sharpening stones for the flat tools in the printmaker's arsenal, but it is difficult to locate stones that match one's curved gouges and chisels. Ready-made grooved stones are available, but the grooves never seem to match the tools on hand, and even when they do, the grooves soon erode into different shapes with use. As the years go by, and one builds up a collection of gouges of various widths and depths, sharpening them becomes increasingly frustrating.
The solution is to make your own grooved stones. Although we grow up thinking of 'stone' as a hard unchangeable substance, it turns out to be quite easy to create the needed shape.
Start with a new, flat, man-made stone of medium grit, and draw a few pencil lines down its length to delineate the width of the channels you wish to make (Fig. 1). Then, using a steel ruler or strip of wood to keep it in the proper line, scratch down along the surface of the stone repeatedly with the head of a large nail. Don't try and dig the entire channel with the nail head, but just score a 'starting line' in the centre of each channel (Fig. 2).
When this guide line is well established, switch to your next 'high-tech' tool - a hand-sized piece of plywood of appropriate thickness, with one edge rounded to a convex shape matching the desired groove, and with a medium-grit sandpaper (about #180) glued to this edge. Rub it along the developing groove, splashing water constantly onto the stone as you do so (Fig. 3). In a surprisingly short time, the groove will deepen out to the required shape.
Three or four different grooves can usually be cut into a single stone this way. Don't throw away the sandpaper block(s) when you are done, as they will also serve to retouch the shape of the channels if they wear unevenly during future sharpening.
This stone will do half the job of sharpening - forming the bevels on the 'outer' surface of gouges and chisels. Stones for the 'inner' curved surface? They are just as easy to make ...
Graphic provided by JOHN AMOSS ILLUSTRATION