Some people use back bevels on bevel-down planes to increase the cutting angle up from the standard 45°. This reduces tear-out. However, some sources recommend these back bevels for block planes only.
Huh?
Yesterday evening I read “Carpenters’ Tools” by H.H. Siegele (Frederick J. Drake, 1950), which is a fascinating little book filled with surprises. In the chapter on block planes, Siegele recommends honing the tool’s bevel at a very low 20°. Then he says you can either sharpen the back flat or raise the back 5° off the stone.
Siegele says this 5° back bevel is more common than sharpening the back flat. Why is it useful? He doesn’t say exactly, but he states the back bevel is an improvement when the bevel has been hollow-ground on a grinder with a small-diameter wheel.
To me, that says Siegele is trying to improve the edge life of his block plane – especially because he is honing at 20° to 23°. But there’s more at stake than edge life alone when you look at all of Siegele’s advice.
In the book’s section on bench planes, Siegele recommends again a low 20° hone for easy woods, but he says you always sharpen the back flat. No back bevel.
So why use a back bevel on a block plane but not a bench plane?
Easy. The wear bevel. When you use any handplane, the part of the blade that gets the most wear is the little bit of metal that faces down against the work. On a bench plane, that means the primary bevel takes the most abuse. That’s not a big deal because the primary bevel also receives most of the work when you hone it.
But with block planes, it’s the back of the blade that gets beat up and worn away. So a back bevel on a block plane is a very good thing. Yes, the back bevel will improve edge life, but it also ensures that your edge will actually be sharp by getting you to hone away the wear bevel.
— Christopher Schwarz
A back bevel thins the b lade profile. While the tearout is reduced, a edge as thin as possible at the point of entry is a positive. All of the planes I use have very thin profiles behind the bevel or bevels in the case of a back bevel. Less compression on the planning surface I assume.
Thanks Chris, this is very thought provoking. I can’t believe I’m saying this about back bevels, but you always seem to find the most interesting topics to discuss.
Mike
The wooden ruler trick?
Instead of bench plane and block plane we might also say bevel down and bevel up. Did those terms not appear in much woodworking literature as recently as the 1950s?
Tico – I really don’t think those terms were in common use until the last 10-15 years. The classic distinction for Stanley was bench planes vs. block planes — thus the #62, which is now commonly referred to as a Bevel-up jack, was termed a low-angle block plane by Stanley.
My memory seems to recall that the term “bevel-up” really came into common use when LV launched their bevel-up planes. I think they may have popularized the term as a way of making more clear what the use of the planes was to a new generation of plane users who hadn’t been trained in carpentry as was the case in the late 19th and early 20th c.
Good point Raney. I find it interesting that Lie Nielsen sticks to the original Stanley designations, using “Bench Planes” for traditional 45 degree and up planes, and “Block Planes” for everything with a lower angle, including the low angle jack and jointers.
Interesting post – especially given that there seem to be a lot of folks lately who disbelieve that there is such a thing as a wear bevel. I note, always, that these are often people working on woods with a springback capacity roughly equivalent to corian.
One thing I think worth pointing out is that this text almost certainly assumes the user is dealing with a standard-angle (20 degree) block. In recent times, though, low-angle (12-degree) bedded block planes are a lot more common. The reason I think this is so important is that putting a 5 degree back bevel on a low-angle block plane is going to leave a clearance of just 7-degrees. In my experience, that’s going to lead to problems in a wide range of woods – only the hardest on the Janka scale would be likely just fine as they exhibit almost no springback.
on an awful lot of timbers, as soon as the sharpness of the blade starts to wear a tad, the plane is going to start acting funky – doing the dive and skim routine that confounds so many new plane users. My shop experimentation is that you’re only completely exempt from clearance angle issues once you get up to somewhere in the 17.5-22.5 degree range. I note that Holtey – who started the current BU craze – always bedded his BU bench planes at 22.5. For most North American woods, anything down to 10 degrees or so is generally OK as long as the blade is sharp, but 7 degrees is starting to really ask for trouble.
Larry WIlliams has been pointing this out for years – but of course the jarrah-using contingent has drowned him out in the popularity-contest known as forums for most of that time. I do think, though, that a battery of readers trying this are going to start to see some odd behavior out of their beloved LAJs, BUS’s, and LABPs.
Jack Whelan has a great analysis of the wear bevel/clearance angle relationship in the appendix of his book, The Wooden Plane. A sample of it is available online here: http://homepages.sover.net/~nichael/nlc-wood/chapters/caop.html .
I just experienced the clearance angle problem Raney mentioned for the first time with my LAJ a few months ago. I love using it, but it started giving me serious grief planing some walnut boards for a tabletop. No matter how often I sharpened, it was getting harder to push and getting noticeably hot after just a few minutes of use. After trying a small back-bevel, I finally figured out that it was the clearance that was causing the problem, and ended up regrinding the bevel and then raising the micro-bevel angle a bit, which was enough to take off about a tenth of an inch and get the back to flat. Works great now, but the prospect of taking off that much metal so often made me switch back to a bevel-down plane for heavy stock removal.
With the L-V Low Angle Jack, what works well for me on end grain work is honing the iron at 25 degrees (it comes conveniently ground at 22 1/2, so a small micro-bevel is easy to add) and putting around a 1.2 degree back bevel, which is steeper than the Ruler Trick but leaving enough clearance angle, just under 11 degrees. That seems to take care of the wear bevel and there’s no loss of keeness with repeated honings.
Wow. Hold that thought, Tico, until Saratoga. I plan on picking your brain some more. This whole forum was great. Thanks, folks.