How to Make Mortise and Tenon Joints
Step1: The first thing you must do is mark out the mortise or tenons and you can start with the tenons. To mark out the tenon you need to start by drawing a line around the entire piece of wood to create the length of the tenon.
The tenon length is usually about 2/3rds the depth of the piece of timber it is being inserted into. Now you must mark your tenon width and it should be around 1/3rd the thickness of the timber.
Check to see if the tenon matches the closest size chisel or mortising drill bit and if it doesn’t modify the lines to match the chisel or mortising drill bit.
Step2: You must now cut the tenon and there are two methods of doing this the first is with a tenon saw. Put the piece of timber in a vice on a slight angle to create a neater and straighter cut and then carefully cut along the lines.
Next put the timber back upright in the vice and mark around 5 millimetres in from each end although it can be slightly more with larger tenons.
Now cut straight down where you marked to create small cut outs on both sides of the tenon, the reason you do this is to create a neater and more flush joint but it also hides any gaps you may have from your mortises if they are cut slightly to wide.
The second method of cutting tenons is with a band saw and all you have to do is cut along the lines like you do with the saw.