Cutting mortises is not my favorite joinery task. I’ve used a number of methods for mortising, both hand-powered and electrical, but until now I’ve put off getting mortise chisels because they weren’t in the budget. Now that Narex offers a decent mortise chisel in my price range, I got myself a little Christmas present:
A 1/4” and a 3/8” mortise chisel, which are the two mortise sizes I most frequently cut.
Why didn’t someone tell me why a real mortise chisel was an essential part of the hand-tool woodworker’s kit? Now that I hold them in my hand and put them to wood, it’s obvious why mortise chisels excel at mortising.
1. Size matters.
I had never put a regular bench chisel up next to a real mortise chisel.
The blade of the mortise chisel is much thicker, providing more strength but also more weight. I think a heaver chisel can cut deeper at one stroke due to the extra inertia. The extra thickness also results in an extra-long bevel, which acts as a ramp for chips as you pop them out of the mortise.
The thickness of the blade and the oval cross-section of the handle make it easy to keep the chisel plumb and square. It’s more difficult to repeatedly place a regular round-handled bench chisel perfectly square to the workpiece. The mortise chisel’s size and shape makes it easier to use consistently while chopping a mortise.
3. Don’t just pry. Scrape.
I sometimes read of woodworkers trying to pry large chunks of waste out of a mortise with the mortise chisel. (I’ve also seen pictures of mortise chisels with tips broken off. Not a coincidence.) As I experimented with my mortise chisel, I quickly realized that you should almost never need to pry hard when removing the waste from a mortise. I could scrape out obstinate chips instead. I have seen quite a few old pros chop mortises but haven’t seen them do this, yet it seems effective.
Once you have chopped into the mortise, loosen the waste by inserting the tip of the chisel into the far end of the mortise. Then, holding the chisel by the blade with your off-hand and by the handle with your dominant hand, pull whole chisel back. The motion is similar to paddling a canoe. Use your off-hand (and not the end of the mortise) as a fulcrum if you need extra leverage.
That way, you preserve the crisp edge at the end of the mortise. Plus, if your hand is the fulcrum, you can’t possibly put enough leverage on the chisel to break the tip off. You’ll hurt your hand first.
Whether you are prying or scraping the waste out of the mortise, there is a surprising by-product. It cleans and smooths the walls of the mortise. How? The mortise chisel blade’s cross-section is not perfectly rectangular but trapezoidal. That turns the bottom edges into sharp cutting edges. They’re not (usually) sharp enough to cut your hand, but they are sharp enough to scrape the walls of the mortise as you dig the waste out of the bottom.
Oh, and in case you were wondering, I haven’t used any other mortise chisels, so I can’t say how the Narex models compare to others on the market. I can say, however, that the Narex mortise chisels have excellent balance: