Popular Woodworking 2006-11 № 158, страница 20

times the value of a smoothing plane. Plum-ley's grindstone rivaled his plow plane and his prized "yellow jaunders" jointer plane as the most expensive tool in the shop. It is not at all clear that period craftsmen had (or could afford) a range of whetstones of varying grits from which to choose. Rather, it seems that workmen were lucky to have a grindstone and one good whetstone - unless of course the workman happened to be French.

Technique

Between Roubo and Joseph Moxon, whose "Mechanick Exercises" was the first English book on woodworking, we have a pretty good picture of how things were sharpened in the 18th century. And that's important because we shouldn't assume they did things the way we do. But I was actually surprised by how similar their methods were to ours. See if any of this sounds familiar:

According to both authors, the basic process was to shape the edge with a grinder or coarse rubstone, then hone the edge until smooth. Moxon recommended 12° bevels for plane irons that work softwoods, 18°-20° for hardwoods. He believed lower bevels cut bet-

Formerly a rustic garden ornament, this stone appears to be rather primitively made and probably dates to the mid 19 th century. Though inconsistent and difficult to work with, it has not been damaged by sitting in water. The other side of it is painted brown, no doubt a decorative touch. Oddly enough the paint may have preserved it.

ter, and higher bevels strengthened the edge. Moxon was also a fan of hollow grinding. This seems a sophisticated approach for 1687:

When you lift the Iron off the stone, to see if it be ground to your Mind; if it be not, you must be sure you place the Iron again in the same position on the Stone it had before; for else you will make a double basil (bevel) on your Iron: But if it be true set on the Stone, and steddily kept to that Position, your Basil will be Hollow, and the smaller your

Grindstone is, the hollower it will be.

Later he talks about using a flat rubstone to grind:

And this they do so often, till they have rubbed the hollowness of the Basil to aflat, and then they grind it again upon the round Grind-stone.

Roubo felt it was important to hone with oil and keep the stone clean:

Oil is useful to sharpen tools on these stones, and it is good that they are always saturated, and that they are always very clean, because the dust which sticks forms to it a grease which spoils them, and prevent tools to take an edge.

Grinding

Operating my grindstone was surprisingly effortless. But the wheel was out of round, nearly impossible to fix and it wobbled from side to side. No tool rest worked, so all my grinding was freehand. Wet grinding, though messy, was nice because I could grind without risking the temper of my precious steel. The sandstone wheel is a slow-cutting abrasive but seems to cut better when soaking wet. Still, a dull V2" chisel took at least 20 minutes to grind. Sandstone left a surprisingly smooth edge. Theoretically, my 20"-diameter wheel

Roubo's grindstone has several advantageous features only recently available to us. It features an integrated tool rest, water cooling, low speed yet plenty of cutting power via its high inertia, and a large-diameter wheel to produce a nice shallow hollow grind. The wide face of the wheel allows a nice straight edge to be ground without moving the tool whatsoever. Fantastic ... until you actually try using it.

When I built my version, I skipped the tool rest. My wheel wobbles from side to side and is out of round about V4". My biggest concern, the effort required to turn the wheel at a usable speed, qu ickly became the least of my worries. This wheel easily spins at 120 rpm and will coast for over a minute! I was shocked. The brown half-bearing is lignum vitae.

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