Back Bevels and Plane Geometry

Bevel-up (BU) planes have been getting a lot of buzz lately – not undeservedly; they’re great planes. Part of their popularity comes from the ease with which the user can adjust the angle of attack – the angle at which the edge enters the wood – for planing various woods in different planing circumstances.

A=bed angle B=bevel angle A+B=C=angle of attack

To adjust the angle of attack, i.e. steeper for difficult grains, you simple hone a steeper microbevel on your blade. Reducing the angle will take a bit more time as the whole bevel must be re-ground to the lower angle. A small price to pay for such versatility.

A=bed B=primary bevel C=back bevel D=included edge E=relief or clearance F=angle of attack

You can easily achieve the same goal in your standard Stanley-style bevel-down (BD) plane by back-beveling the blade.  What’s back-beveling, you ask? It’s simply adding a small bevel on the otherwise flat back of your plane iron. Most BD planes bed the blade at 45° – the angle of attack. This is a good angle for most work. With difficult grain,that’s prone to tearing out, however, you may benefit from a higher angle of attack, say, 55° or even higher. With higher angles of attack, the fibers are less likely to be levered up by the blade to tear out of the surface you’re planing. You do have to push harder, but you can achieve a smooth surface where you may not have been able to with the lower angle. The amount of back-bevel can be quite small; the wood only sees the first few molecules of the edge so a back-bevel as small as 1/64” should suffice. And there is no need to flatten the rest of the back – a real plus.

The only down side to the back-bevel is that, if you wish to revert to a lower angle of attack, you’ll have to grind the primary bevel back past the back-bevel and start over. That’s not different, if you think about it, from the blade bevel in the bevel-up planes, where you have to shorten the blade to increase the bevel angle. With a bevel-down blade, you have to shorten the blade to decrease the angle. My friend, Brian Burns, guitar- and tool-maker, wrote a 32 page booklet about back-bevel sharpening, Double Bevel Sharpening. He’s condensed years of experimentation into an interesting tome complete with clear illustrations that even includes instructions for building his ideal honing system. Brian says that a blade’s angle of attack should be adjusted for different woods the same way a metal-cutting tool is ground at different angles for different metals. Once you have a repeatable method for dialing in the back-bevel it only takes a few extra strokes at the sharpening station to avoid tearout in difficult woods.

Happy New Year, everyone!

The illustrations above are by Martha Garstang Hill, who created the beautiful hand-drawn illustrations for The Perfect Edge. Thanks, Martha.

About Ron Hock

Owner of HOCK TOOLS (.com) and author of "The Perfect Edge, the Ultimate Guide to Sharpening for Woodworkers"
This entry was posted in Uncategorized. Bookmark the permalink.

5 Responses to Back Bevels and Plane Geometry

  1. kaz says:

    thanks for clear explanation and great help.

  2. Pingback: Two Better Than One? « The Sharpening Blog

    • rose says:

      Please disregard previous and forgive me for an ignoramus! believe it or not, I’m one of the ten people in the world who’s new to all this blogging stuff. I just realized that if I pressed “Two is better than one?” link the whole entry from Ron and the long informative discussion would be revealed. The universe is unfolding and I’m following up the links…… I think I’m a little intimidated by this new LN#62 and hoping to learn how to treat it right, which has me running in 12 directions at once. Wish me luck!

  3. Rose says:

    It’s a year on since you wrote this blog, but I hadn’t been gifted a LN long angle jack plane then… So here’s the question: Do you use back bevels with low angle bench planes? I’ve read about David Charlesworth’s method for flattening the backs of planes giving a very, very, slight back bevel, on the other hand Brent Beach insists that almost every plane blade needs definite micro bevels on the back, Leonard Lee doesn’t seem to mention this particular situation, and I haven’t received my copy of your book from Lee Valley yet. And the internet is driving me nuts! I’d love to hear your opinion on the subject. Oh yes, and a Happy new New Year to you.

  4. Pingback: Sharpening Angles for Bench & Block Planes « Virginia Toolworks

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s