Woodworking Tips
Woodworking Tips Index
Fitting a Mortise & Tenon Joint

No matter what method you use for making a mortise and tenon joint, there’s still a good chance that you will have to do some “fine tuning” to get a perfect fit.

Undercutting The Shoulders. One of the most common problems encountered with a mortise and tenon joint is a gap between the two mating workpieces. This is caused by a shoulder that isn’t perfectly square or cut cleanly.

To avoid this problem, I like to undercut the shoulders of the tenon slightly with a chisel. This allows the edges of the tenon to fit tight to the mating workpiece when the joint is assembled, see photo.

Removing Stepped Shoulders. Another common problem when cutting four-shouldered tenons is a stepped shoulder. If I run into this, I don't try to correct it at my saw. Instead, I come back after and pare them flush with the side shoulders, as shown in the photo at right.

Fitting a Mortise & Tenon Joint
Undercut Shoulders. To get a tight jointline, slightly undercut the shoulders of the tenon with a chisel.

Fitting a Mortise & Tenon Joint
Remove Stepped Shoulders. Cut shoulders on edges of tenon slightly proud, then trim flush.

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