Chisel bevel angle question

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What's the recommended bevel angle for an English pattern mortise chisel? - also known as a "pigsticker". Since they're mortise chisels, you'd think the bevel angle would be maybe 35* but I have several of these chisels and they came with a wide variety of bevel angles - from maybe 25* to about 35*.

What seems reasonable to me is to put a primary bevel of about 25* on the chisel to allow it to penetrate deeply and to put a secondary bevel of maybe 30 to 35* as needed to give the edge some strength. For those of you who use these chisels, "What do you do?"

Mike

[added note] When I cut a mortise by hand, I usually drill out the majority of the wood first so almost any chisel will serve. But these English pattern chisels are really appealing. The look 'mean', they work great, and most of them are old - probably late 1800's (they have laminated "cast steel" edges). And they're fairly inexpensive, especially if you buy one with a damaged handle. Collectors seem to want chisels with pristine, original handles so the damaged ones go cheap.
 
Mike, wish I could be of more help, but your thoughts on the 25* with a 30~35* secondary bevel seems to be in line with what I've heard from others. I thought there might be something on OldToolsShop, but I couldn't find it quickly. It seems that Derek Cohen has written something on the subject.
 
Thanks, Ed. I decided to go with about 27.5* for the primary bevel and between 30 and 35* for the secondary bevel. I think that will work well for me.

Mike
 
Sounds like you got it about right Mike... you could check at Toolsforworkingwood for a definitive answer, they sell new English pattern mortise chisels and tend to have a lot of info too.

I've got one oldish mortiser that was ground with a rounded bevel, seems to work fine. I think the idea was that this tends to push the chips out easier than a straight bevel, which tends to get stuck in the wood. Never made much of a study of it myself. Only drawback to pounding them out all by hand is it drives the wife crazy :rofl: -- I did all the mortises on our bedframe that way, and she only put up with it because I'd taken so long to build the bed! :doh:
 
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