I picked up this I. Sorby English mortise chisel with the Punch logo the other week and finally got it cleaned up and put back into service. The chisel is 33cm (13”) long and 7mm (a touch over 1/4”) wide at the back.
The handle is an oval shape and tapered in both directions. The end of the handle is slightly domed to help prevent a glancing mallet blow from chipping the side of the handle. A hard leather washer separates the handle from the bolster.
The cross-section of the blade is a trapezoid which greatly reduces the chances of the chisel getting jammed when you whack it deep into the wood and lever the waste.
Unlike the Ray Iles English mortise chisels being made today from D2 steel, old mortise chisels were made from mild steel with a cast steel cutting edge strip hammer-welded to the back of the chisel. That is the darker gray area indicated between the red lines below. The transition between the primary bevel and the front face of the chisel is rounded over which assists when levering the chisel to eject the waste.
The primary bevel is sharpened at 20 degrees allowing the chisel to plunge quickly into the wood.
A 35 degree secondary bevel helps to strengthen the cutting edge.
Here it is after cleaning and sharpening the blade and giving the handle a couple of coats of BLO and wax.
I tried it out in some scrap softwood and was amazed at how easily it attacked the wood, yet I was using less force than I commonly used on my bevel-edged chisels when mortising. There are so many little design features in these chisels that culminate in a tool that does what it is meant to do and does it with authority. I’m calling it THE ENFORCER. Not bad for £7.99.
In the next episode, I’ll discuss the different ways to use an English mortising chisel, and let you know which method I like best and why.
-- Andy -- Old Chinese proverb say: "If you think something can't be done, don't interrupt man who is doing it."