Corner Chisel

I bought a corner chisel (as well as other chisels) made by Barr. The bevels on the corner chisel are skwed at about 85 degrees. Where the two bevels meet in the corner they come to a point such that when in use the chisel will first cut the corner and then thes sides as the chisel is tapped with a mallet.

It is not obvious to me. Why is the chisel made this way?

Thanks in advance,

Joel

If the chisel was ground at 90 degrees it would wander all over the place.

The effect of grinding it at an angle favouring the corner of the mortice is that....the corner is the lead cut and once that is started the balance of the cut is going to follow the "lead" of the corner, without straying from the corner.

The lead corner cut is going to give way to a slicing action across each face of the mortice rather than a "forced" corrective cut across each face simultaneously, which would give rise to the chisel following the grain and being very difficult to control.

Hope this helps

This is probably not a correct engineering answer but hey it is 02:30 in the morning!!

chisels and planes cut better at less than 90deg. to the grain
your framing chisel would be faster at 85deg but it would be difficult to make a square mortice bottom, i think.
-Mark. in ontario

Thank you both for your replies.

As they say, the devil is in the details. And I have a lot of details to learn!

Thanks again.

Joel