I’ve seen several posts here on LumberJocks related to someone making a mallet for chiseling (not the round ones for carving) and wanting to know what the best angle is to put on the head. I put together a complete mallet making post that includes an angle method recommended by a few old Timber Framing Books as well as some woodworking magazines.
Here is the complete source of this post which includes making the mallet from start to finish, and in case you are only interested in the angle method, you can jump to it here. Otherwise the condensed version is below:
A mallet with a squared head like this one makes it difficult to hit a chisel without either deflecting the chisel off its line, or contorting the wrist and ending up with extra torque that fatigues the wrist more than necessary.
In ideal use, a mallet is swung such that either the woodworker’s elbow pivots in heaving driving, or the wrist pivots for light taps. Either way the mallet swings in an arc so it is essentially traveling in a circular path. When the head strikes the chisel handle, the closer the face is to striking the handle head-on, the better.
If the handle is perpendicular to the face of the mallet at impact, it is less likely to deflect and the amount of twisting force on the mallet is reduced, making for less abuse to the hand and wrist.
The ideal angle is a combination of how you swing, how long your arm is, how you grip the mallet and how long the mallet is. It would be difficult to measure them all.
They all influence the angle that would be needed.
Fortunately, with a bit of string, and a couple of pieces of tape, you can quickly transfer the best angle to your mallet. Keep in mind this is specific to YOU and the MALLET.
1) Tape one end of the string to the far corner of the top of your mallet head.
2) Hold the Mallet as you would normally swing it. (take a few practice swings to make sure)
3) Determine the pivot point for how you swing your mallet. (in the photo above, the pivot point is my elbow) and tape
4) Pull the string tight and tape it to the pivot point.
5) While you are still holding the mallet as though you are swinging it, have someone mark with a pencil where the string crosses the lower edge of the mallet head.
6) Use a bevel gauge to transfer it to the other face of the mallet
7) Cut the faces to that angle.
It will seem too steep when you look at it, but when you use it, it will all make sense.
-- Galootish log blog, http://www.timberframe-tools.com