Posted by
Easy WoodCraft on
Mar 27, 2017
A common paring task for a chisel is trimming or cleaning tenons for a mortise-andtenon, a slip joint, or a stub-tenon-and-groove joint. There are a couple of critical areas of the tenon that usually need attention: the cheeks and the shoulders.
Sides
To clean up the sides of a mortise, choose a sharp chisel that's fairly wide (
right photo). Take care to keep the chisel vertical (a guide block clamped to the workpiece helps), and take light cuts. Skewing the chisel also produces a cleaner shearing cut.
Ends
Mortise ends often require paring, either to size the mortise correctly or to square up corners (
left photo). Although a lot of folks advise using a chisel that's the same width as the mortise for this, I've had better luck with one that's slightly narrower. This way the chisel doesn't get jammed between the sides, and you don't have to rock it to get it out. Rocking like that can enlarge the mortise, creating a sloppy fit.
Bottom
The bottom of a mortise is a difficult area to clean up, since access is limited by the sides and ends. The best way I've found to do this is to use a chisel with the bevel up and take light, scooping cuts (
bottom photo). Avoid the temptation of using the top edge of the mortise end as a fulcrum point for the chisel: You'll only crush this edge and end up with a weaker joint.
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