Dating back thousands of years the mortice and tenon joint is one of the oldest ways to join two pieces of wood, comprising a mortice hole and tenon tongue which fit exactly into one another. It’s a versatile joint that can be used in many different types of woodworking, from fine furniture to large oak framed buildings.
Tools needed for cutting mortice and tenons by hand:
For cutting tenons by machine:
Prepare material for both parts of the joint.
Joint is set out according to ‘Rule of Thirds’, whereby the proportions of the joint are approximately divided into thirds, thus if the tenon rail is 20mm thick, the mortice chisel is approx one third, so 7mm (arrowed).
Set the mortice gauge pins to the width of the chisel.
Make two dots (arrowed), check from each side to ensure tenon is central.
Mark depth of tenon, approx two thirds depth of the second piece of timber (arrowed). This is the shoulder line, which should be heavily knifed.
Holding the wood in the vice, make parallel lines all round.
Set marking gauge to 6mm, gauge line all the way round (arrowed).
Set marking gauge to timber width – 6mm, mark width of tenon (arrowed).
Completed marking out of tenon on end grain.
Lay tenon piece on mortice material, mark position of mortice in pencil (arrowed).
Transfer lines across wood.
Set mortice gauge to mark position of mortice, don’t alter the distance between the pins. Pencil in the waste.
Mark the width of the mortice (arrowed) with a knife.
Chopping The Mortice
Clamp the mortice position over the strongest part of the bench (the leg).
Stand at the end of the bench when chopping to align the chisel vertically.
Chop out the waste, using the chisel as a lever to remove the chippings. Stop 2mm (arrowed) from the knife lines.
Check for depth, which should be 3mm longer than the tenon.
Two final cuts, one at each end, on the knife line. Check for square.
Cutting The Tenon
We have detailed two ways you can cut a tenon; it can be cut either by hand (A) or with a bandsaw (B). Cutting by hand demands more control and can be more difficult, particularly if you are just starting out.
Cutting By Hand (A)
Make two triangular cuts, one from each side.
Complete the cut but sawing horizontally to the shoulder line.
Make two further cuts on the broad faces.
Position tenon piece on the bench hook.
Saw off cheeks from tenon all round, leaving 0.5mm waste on the shoulder line (arrowed).
Position a wide chisel on the knife line, sight for square and chop the shoulder line. Alternatively, use a shoulder plane.
Use block plane to chamfer end of tenon (arrowed).
Test to fit, joint should push together with moderate hand pressure only.
Cutting With a Bandsaw (B)
Check bandsaw blade and fence are square to the table.
Make four saw cuts on waste side to finish at shoulder line.
Mitre fence and ‘stop’ to cut off waste tenon cheeks.
Tenon cheek waste removed.