## Hand Tools

Subject:
Re: it depends on the plane
Response To:

steve voigt
Replying to several posts here…

Warren: Nicholson was of course talking about a wooden plane when he talked about a rounded bevel. I make cap irons for wooden planes, so I use a rounded bevel. But I don't think it matters for a metal, stanley-type plane. The purpose of the curve is to get the cap iron out of the shaving's way, quickly. This is crucial in a traditional woodie that has a steep wear somewhere between 70° and 85°. A Stanley-type plane has a much more forgiving escapement, so I don't think the curve is a big deal.

Some numbers: a so-called "improved" cap iron is 1/8" thick and has very little spring, so the 30° bevel will start around 7/32" from the tip, if my math is correct. When I make a cap iron, the curve starts about 9/16" from the tip, nearly twice as far. the angle stays relatively shallow as long as possible, then accelerates rapidly near the tip. Put simply, it gets out of the way faster than a flat bevel does. That is the point of the rounding.

Dave: continuing with your automotive metaphor, I have long compared 50° to a comfortable sedan, or even better, my neighbor's lovely old Benz wagon, and 80° to my uncle's corvette. In the Benz wagon, there is a huge range on the accelerator pedal between coasting and flooring it. On the Vette, it's all or nothing. Same with the clutch--I vividly remember failing on the vette as a kid because the clutch was too sensitive. For me, with 80° it feels like the difference between "too close" and "not close enough" is just a few thousandths, whereas 50° or so feels more forgiving.

Patrick: it would be interesting to do some math here, and you're probably better equipped than I. The simple part is that the greater the angle, the closer the "impact point" will be for a given setback. The complicated part is that the chip will be bent at a greater angle as well. So obviously a greater angle will potentially reduce tearout more, but it will also increase the required force a great deal, which matters because we are humans and not Kato/Kawai planing machines.