double bevel for higher bench plane angle

[Mark Kosmowski]

Let's say you had an excess of a particular size bench plane and were willing to mess with the blade grind. Better yet, let's say you also know a machinist with an excess of tool steel and a better set up home machine shop than most of our woodshops are for wood. Would it be a horrible idea to put a bevel on the flat side of the blade to increase the angle of attack?

[jerry nazard]

It is a good idea. I've been putting a 12 - 15~ back bevel on a No. 3 and 4 for about a year now - primarily for use on white oak. It doesn't take much honing to get a 1/32 back bevel, and its not much trouble to remove it, either. One thing I have learned is that the blade must be really sharp, so I hone to .05u on 3M paper. The plane will be a bit harder to push, and tearout will be less easy to create....

[David Weaver]

As stated, it's far from a bad idea, it's actually a very good one.

When I do it, I only use a polishing stone and make a very small one. The effect is the same and it can be honed off very easily if you want to on a medium stone.

[Tri Hoang]

It's done sometime for difficult wood. A standard blade honed extra sharp would eliminate most problems. However, when you need it, you'll appreciate the high angle.

I think getting a high enough back bevel to combat difficult wood is more trouble than it's worth for most planes bedded at 45*. The max front bevel you can have on these is around 35*. To get the cutting angle at 55*, you must have a 10* back bevel. This would reduce the effective cutting edge to around 25*. In such a condition, the blade would get dull pretty quickly.

This is a case that a bevel up plane is more handy.

[Andrew Gibson]

One of my concerns with say taking a vintage Stanley and creating a higher angle would be that the plane is to light to perform optimally with the higher angle. This could very easily be my inexperience talking. I would think that a higher angle of attack would be better suited to a plane with greater heft, so that it's momentum would not be as easily lost.

[David Weaver]

It's done sometime for difficult wood. A standard blade honed extra sharp would eliminate most problems. However, when you need it, you'll appreciate the high angle.

I think getting a high enough back bevel to combat difficult wood is more trouble than it's worth for most planes bedded at 45*. The max front bevel you can have on these is around 35*. To get the cutting angle at 55*, you must have a 10* back bevel. This would reduce the effective cutting edge to around 25*. In such a condition, the blade would get dull pretty quickly.

This is a case that a bevel up plane is more handy.

Other way around. It actually blunts and strengthens the edge. It is listed in odate's book as a way to improve edge durability in tough woods or for new irons.

With a 20 degree back bevel you can actually plane backwards into the grain on most wood. The finish won't be like it is with the grain with a lower angle, but it will be without significant tearout - no damage to clean up.

[Tri Hoang]

Other way around. It actually blunts and strengthens the edge. It is listed in odate's book as a way to improve edge durability in tough woods or for new irons.

With a 20 degree back bevel you can actually plane backwards into the grain on most wood. The finish won't be like it is with the grain with a lower angle, but it will be without significant tearout - no damage to clean up.

I had Odate's book but perhaps I skipped over this fine detail. Are you saying that the blade is blunt but not dull or are we saying the same thing here?

[David Weaver]

Blunt just referring to the total angle of the iron - it should be the amount of the bevel on the bevel side of the iron plus the back bevel created, so instead of having 35 degrees (like with charlesworth's method on the final bevel), if you had a 10 degree back bevel, it would be 45 degrees.

You can still have it polished to a half micron or whatever you like to do, but it will feel less sharp, the same way a very sharp mortise chisel still feels less sharp than a so-so sharp paring chisel set at 20 degrees.

A plane with a 10 degree back bevel works really really well.

One with a 25 degree back bevel works really well for its intended purpose, but it is really really hard to push. You can't, however, manage to create any tearout with it in a hard wood. It's just so hard to push that once you're done with your intended use, you realize that you wouldn't want to do that all the time - it's basically a scraper at that point.

As someone said earlier in this thread, it seems intuitive that it would be hard with thick shavings - I can't move the plane with shavings more than a couple of thousandths, but for the number of times you'd have to do it, you could tolerate thin shavings and appreciate that you aren't clearing up catastrophic tearout.

Not a great trick for softwoods, just like scrapers - leaves a fuzzy surface (well, at least in comparison, you could still finish it if you wanted, just maybe not with wax only).

As far as odate's book, IIRC, it came up when he was talking about new irons being somewhat brittle and/or the tendency of silica impregnated woods to chip out irons at standard angles. He was probably talking about teak, but cocobolo comes to mind for me - I have had several blocks of it where you resaw it on the bandsaw and it sparkles - you know you're going to do a lot of sharpening then. I thickness my plane tote blanks by hand so that I can cut a small bit off my turning blanks, etc. I can dull an A2 iron taking <1/4" of cocobolo off of a piece about 5x5 with a rank cambered jack plane. It's awful stuff - I see why there isn't much old furniture made of it, and I see why japanese woodworkers would back-bevel their irons to try to stretch out the time they lasted.

[Brian J. Williams]

I've run a 10 degree back-bevel in my 4-1/2 on QSWO, and it does help, but I think running a heavier-than-original iron would probably help more.