What is a good sharpening angle for dovetails, which involve some (mild) chopping cuts? Last night I was cleaning up some tenon shoulders and my chisels edge didn't seem to hold up well. Wood was white oak, and the angle was 25 degrees. Chisels in question are good ones (Barr).
Given the reputation, not to mention price of Barr chisels, I'm surprised at your report.
Assuming you're talking about the sharpening angle at the actual cutting edge (as opposed to grinding, primary and other bevels) you might go a little higher, but certainly no higher than 30 degrees (which is what I used for mortising). If they still don't hold up, a "conversation" with Mr Barr may lie in your future,
To avoid your question, I'd suggest removing the bulk of your waste with a fine bladed saw (e.g. coping saw, small bow saw, or jewellers piercing saw) and then performing only final paring with chisels.
BugBear
Am a little confused. The subject line refers to dovetails but the text is about tenons. The former may involve some chopping cuts but the latter should be paring/shearing cuts.
Tenon shoulders first:
If you're "cleaning up" tenon shoulders with a bench chisel or two, you should be making paring cuts, not chopping cuts. The former are done with only hand pressure and a rocking, shearing motion rather than a mallet driven square chopped action. (second set of illustrations on this page show the rocking/shearing thing. the next page shows an animated version of the idea)
If you're chopping the waste between dovetail pins or tails in oak then Frank Klausz's Three Chop Cuts Per Side (which works for the pine he prefers to use) probably will kill your chisel's edge. Less mallet force and more, lighter chopping cuts will get you there with less chisel wear and tear, though it will take a little longer. A set of butt chisels sharpened at the bigger bevel angle may also help. Because they're shorter, they're easier to position and a shorter tool length means less torque on the cutting edge if the mallet blow/tap is not directly down the long axis of the chisel. Lots of subtle things involved with hand tools and there's a very good reason for all the "special" versions of hand tools.
Consider using a coping saw to get most of the socket waste free and then pare the rest. Much easier on the chisels and with a little practice, just as fast.
hope this helps a bit.
charlie b
Cripes you actually paid for Barr chisels??? (I think I admire that...) Alex
Charlie you don't mind if I DL'd the .pdf do you? Alex
Not at all. My intent was to get folks to try handcutting dovetails. If the info I put together gets someone to try it then I'm a happy camper. And don't overlook the link to the site with a compendium of dovetailing info.
charlie b
I'd think 30 degrees would be better for chopping, 25 for paring.
Your post reminds me of a scene from one of those make over shows I caught a week or two ago. A guy "borrowed" a chisel and hammer from the carpenter's tool box without permission. While he was chopping glazing compound out of a window the carpenter came over angrily and said "tell me you're not using a $125 chisel to do that..." as he grabbed the chisel from the borrower's hands and walked away. It was a socket chisel with a band at the top of the wooden handle... I thought at the time it was a Barr chisel. ;-)
John
Each Barr is hand pounded, awesome. It drives the carbon content closer together to a more concentrated state, creating serious strength.
Alex
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