Part 2: Discs, Stones and Wheels

In Part 1 we looked at sandpaper. Here, we'll look at grits relative to some other applications.

For a long time, grits were made mainly of natural materials eg stone. Other materials were (and still are, sometimes) also natural – garnet, … even diamond. Nowadays however, most are synthetic which allows more consistent particle sizes and much less in the way of softer in-between filling stuff that slows the grinding. I still have a couple of natural stones (one still in its box –   Genuine Yellow Lake Oilstone, from USA) which sit on a shelf awaiting auction prices...

Discs: these are used, with velcro-type backing, on fairly flexible conical foam rubber bases held in an electric drill – normally used on the lathe on gentle curves and on bowls (inside and out). They vary in diameter from 3 inches down to about 1½. The abrasives I use in this mode are of the older type papers (on stout fabric backing), for initial and earlier sanding, prior to finishing by hand with the finer, more flexible web-type pads.

Stones: a variety, little used nowadays if at all, except for the diamond grit one, which is used occasionally for flattening or shaping. Sharpening stones will be of grit sizes in the low hundreds – p200 or p300 perhaps, while the honing stones are commonly in the thousands and can reach to over p10,000.

Wheels: the commonest are the fast running ones of about 6 inch diameter and grit sizes probably rather coarser than p60. By careful, gentle use you can get a good sharp edge by gently twisting and turning the tool against the wheel, looking for a line of sparks at the very edge. I said 'you can', meaning I have great trouble with those things – they're steel eaters. They are quite good enough for turning but create too much extra work (getting rid of the scratches) for carving.

Incidentally, looking at the edge of a blade, moving it around in the light, if you actually see the edge … it needs sharpening.

Do you remember the old Knife Grinders? The man who came around on a bicycle, parked in a more-or-less central point, or points, in your area, connected a grinding wheel in place of the back wheel, rang a bell or tooted a horn and waited for customers? I remember that much ... and that the grinding wheel must have been well over a foot in diameter, perhaps two and that he charged pennies. I'm thinking that his wheel will have been no or little coarser than p200 and he must have had a smoothing wheel and probably a honing one as well... I reckon that, by the time I was old enough to remember that much, he must have been well on his way out – and that many of his clientele were more charitable than edgeless.

Articles by Rod

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