Back Beveling Explained

Jerry Thompson asked: Would someone please explain back beveling to me? I have seen it mentioned many times during hand plane discussions. What is the benefit from it? How is it done?, etc., etc.

Paul in NJ: If you put a back bevel on a bevel down plane blade, i.e. a Stanley or Lie-Nielsen #4 for instance, you increase the effective cutting angle of the plane by the amount of back bevel you add. To increase the effective cutting angle for a bevel up plane you just increase the angle of the primary bevel. Increasing the effective cutting by using a back bevel may help with the tear out of difficult grain. Another use of the back bevel is with pitted plane blades. Rather than flatten the entire back which is tedious if you have rust pits, you add a back bevel to get to clean metal.

An easy way to back bevel is with David Charlesworth's ruler trick. You simply put a 6" metal machinist's ruler on top and at the end of your honing stone. The ruler lifts the back of the blade as you are honing and automatically adds a slight back bevel.

Mike W: To add to Paul's excellent explanation, on a bevel down plane that is bedded at 45°, placing one of those 6" rulers on top of a 2" wide stone, flat, and with the plane back laying on the stone so the edge is on the opposite side of the stone from the ruler, back on the ruler and honing will give a couple degrees of back bevel.

This makes the effective pitch on that plane 47° or so, depending on how far the blade's edge projects past the ruler's edge. Using a honing guide is a good way to add more back bevel consistently. So for instance, adding a 10° back bevel now makes the effective cutting angle of that plane with a bed of 45° equal to 55°, and so forth.

All that is needed to achieve the efficacy of the back bevel, is to hone one about 1⁄32" or a little less. Doesn't take much.

One if the issues with using back bevels is consistency, which is why without a honing guide Charlesworth's method is a good one, but anything can be used, if used with consistency.

Back bevels are a good way to plane wood that is tearing out, such as wood with reversing grain. It is, though, less than ideal unless you either always work in such wood, have a couple planes for this use, or have more than one iron for said plane—which isn't a bad idea for a smoother anyway. The reason a second blade is a good idea is if you decide to now lower the effective cutting angle by removing the back bevel you have to grind it out.

Jerry Thompson asked: I am still a little confused. Does the back bevel go on the back of the plane iron, i.e., the opposite side of the bevel?

Greg Sloop, Portland Oregon: Yup. From the perspective of the plane it probably should be called, more appropriately, a front bevel.

In short, the main bevel trails the cutting edge of the iron. The back bevel would be in front of it. It would increase the effective cut angle from say, 45° to 45° plus the back bevel angle.

Clear as mud?

Frank D. in Montreal: The ruler trick gives a back bevel but I think it only gives a 1 or 2° angle. Usually back bevels are around 5 or 10°, so a ruler isn't quite thick enough for this. I know I'm splitting hairs a little here, but I just thought I'd point it out.

Les Winter asked: When you hone the main bevel, you create a burr and you remove it by backing off on the back side. After you hone the main bevel and you hone a back bevel, how to do you get rid of the burr from the back bevel?

Steve Elliott: I'm a convert to using back bevels on plane blades because it speeds up sharpening and gives me a keener edge than I've been able to achieve without a back bevel. The quality of honing I can get on a tiny back bevel is better than I can get when I have to hone the flat back of the blade.

I usually use a back bevel of 2 or 3° even when I don't want a higher cutting angle, just for the speed of sharpening and the final edge quality.

Frank D. in Montreal: I made a distinction between back bevels for ease of sharpening and back bevels to help with tearout. I once described David Charlesworth's ruler trick on another forum as a back bevel and he showed up to say that his ruler trick was not a back bevel as is normally undertstood (used to raise the effective planing angle, which the ruler trick didn't accomplish to a significant degree). It is a back bevel though, I just tried to make a distinction between the two for the person posted the original question. Oh well...

William Duffield, on the Cohansey: Strop the blade across the palm of your hand a couple of times on each side, until you don't feel the drag from the wire edge. For the faint of heart, you can use a leather strop, or a piece of hard maple instead of your own leather. I used to use the knee of my blue jeans, but that led to premature denim failure and more cutoff shorts than I really needed.

Mike W: What William said. In reality, the burr created in making the back bevel is insigificant in size, extremely weak and will at the slightest provocation break free. Which is what a light stropping causes it to do. I often use my shirt or jeans. Couple swipes and that's it. If one were to seriously remove metal in creating the back bevel, it would require more attention.

Adam Cherubini: Don't laugh at me but I've found it helpful to remember that the sine of 1° is 17 thou (.017") So if the ruler is .032 and 2" from the edge, that's one degree. Moreover, sine is pretty linear at low angles, so you can just multipy by .017 to get the sine of 5°. So you'd need a ruler .10" thick, 1" from the edge to get a 5° back bevel.

I think about this stuff when I'm sawing a tenon shoulder. If I lose the line by .010" over 2" I figure I'm off ¼ of a degree.

Paul Kierstead: Actually, that is pretty handy. I got the sin/cos of the major angles ground into my brain years ago, but never really thought to stick 1° in there. Thought woodworking would be a lot easier if it were in grad...