Gentle Galoots -

Not a rant, but a suggestion that we recall, IMHO, that woodworking 
is more art than science.  There is really no "correct" angle for a 
mortising chisel, save that which works best for you.   There's a 
probable range - e.g., 20 to 40 degrees.  No apoplexy among the 
purists, please - hear me out before sharpening the rope.   I admit 
to having been guilty of repeating the commonly held mantra requiring 
that mortise chisels be sharpened steeply  - at perhaps 35-40 deg 
plus secondary - so as to withstand the rigors of such brutal 
work.  "There's the right way t' go f'yer mate - make 'er plenty 
stout"  ... and harder to beat to depth, too.

In truth, craftsmen (persons? - there's no innate gender specificity 
in my thoughts about this or much of anything)  approach many 
differing materials, with widely differing levels of imposed force, 
and with varying qualities of chisels.  Steel has improved immensely 
in quality, and even a low-born chisel (with a blue handle, eh?) is 
likely to perform surprisingly well.

The person expertly flailing away trying to make a living at it will 
work differently from most amateurs.  Who's actually turned an 
edge?  Broken off a bevel?  If you're not experiencing problems with 
the tool as used in your hands, then the shallowest successful angle 
is right for you, and will work the most easily.  Sharpness is likely 
to have more influence than bevel angle.

I'm not so sure that convex radiusing is a convincing 
argument.  Concave (hollow ground) should release even more easily 
because relative angle will cause bevel to back away from wood faster 
upon retraction and leave more room for springback of compressed 
fibers, but that of course weakens the edge.  Release should perhaps 
then be considered to have been harmoniously optimized with bevel 
strength in a flat-ground configuration .  A convex radius in 
extremis seems more to me like approaching the cut with a branding 
iron.  That's yet another challenge - the added stength of a flat 
grind over a hollow grind is technically inarguable, but I'll bet 
that most of those who hollow grind don't have a vexing problem with 
breakage ... eh??

All that said, the true old pros who were working oak with biceps 
larger than two of our legs, cask-sized mauls,  and older steel 
needed pretty stout chisels, with the modern lesson devolving finally 
to a suggestion to increase the bevel angle as increased skill, 
confidence, and energy begin to yield tool damage.  (Uhhhh - yup, I 
exaggerated, but the point remains.)  Let the tool tell you - if it's 
happy, then be happy right along with it.  If it's requiring a good 
honing every whipstitch, try a steeper and broader secondary as a 
trial, then evaluate - is it angle or steel quality?  (BTW - and 
again IMHO - chisel steel should be in the range of 58-62 Rockwell C 
and fine-grained.  Needs to be able to take a scary-sharp edge, take 
a honing readily, not edge-turn in the work, and not be breaking off 
under lateral stress.)  ... and "sharp" is the keyword.

Once, after acquiring a new mortising chisel, I was disappointed to 
discover that it sported only a 25 degree bevel. Haven't damaged it 
yet (and I'm not shy about smacking a chisel, either!), so I'm happy 
and better educated for the experience.   (I could probably damage it 
in ironwood or ebony, but haven't yet tried that - too expensive for 
casual experimentation.)  Added a 35 degree secondary as I learned 
more, and happily keep it lethal with not much effort via a hunk of 
glass and some wet-or-dry.

Keep yer tote tight,

---John
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JWPopp "Poppajohn" (jwpopp@p...)

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