Mortise and tenon sizing

[Juicegoose]

Guys I was going to practice some mortise and tenon work on the door frames of the cabinets i'm building the wife. The stock is 2" wide by 3/4" thick. Is there a general rule of thumb for the depth of the tenon and size? or is it just using the force!!

My force tells me to make it 3/8" thick and 1" deep by 1" wide. What you guys think?

[Bombarde16]

My force tells me to make it 3/8" thick and 1" deep by 1" wide. What you guys think?

I prefer to use the Schwarz, myself.

What sort of doors are these? If they're frame and panel, the M&T's are usually the same as your panel groove, i.e. 1/4".

[Juicegoose]

Aww yes the force is strong with you. I will be utilizing frame and panel and will indeed be cutting a 1/4" groove for the panels. So 1/4" wide by the 1x1 margin I stated earlier?

[Bombarde16]

So 1/4" wide by the 1x1 margin I stated earlier?

An inch deep is ample (and within the range of most 1/4" router bits) but the width deserves more attention. Haunched tenons are customary for door frames, so the tenon width is 2" minus 1/4" for the depth of the panel groove and minus the depth of the haunch. I don't know the rule of thumb for haunches; but would guess at least 1/2". Any smaller and the end grain of the stile may blow out. I vote 1 1/4".

[adamking]

Typically, you make tenons 1/2 the thickness of the stock you're cutting them from. The width is typically 1/2" narrower than the width of the stock. The length of the tenon is typically 1/16" shorter than the depth of your mortise.

Also, a great rule is to make your mortise first, then simply size the tenon to fit the mortise. Cuts down on a lot of measuring.

[bignoise]

Also, a great rule is to make your mortise first, then simply size the tenon to fit the mortise. Cuts down on a lot of measuring.

Yeah that is the way I like to do them too. I always make a slight cut on my tenon then check the fit before committing to cut by laying the tenon section on top of the mortice section and looking down to check that the cuts in the tenon line up with the mortice. (hope that makes sense )

I was taught mortice and tenons in thirds. The tenon is 1/3 the thickness of the material and the haunch is 1/3 the width of the tenon (if a haunch is required). Often the tenon is bigger than a third depending on what size mortice chisels you have.

[Pete Bennett]

Yes the thirds method is customary here in Europe to decide the thickness of the tenon. It was how I was taught way back in the fifties. (Subject of course to the mortice chisels available.) Also tenon width is determined by the stock size of the piece being tenoned, (not always the same size as the piece being morticed. Haunches are rarely less than 5/8ths of an inch for the reasons mentioned. The advice concerning panel groove is important as any one cutting a tenon narrower than stock size less depth of groove plus haunch (if you are having one) will readily testify. It's a bugger, and believe me we've all done it. Like Chris I was always taught to cut my mortices first and lay out my tenon from them. Even though I now have a mortice machine and regularly cut my tenons on the bandsaw I still do it the way I was taught, it's just quicker and less work now. Hope this is of some use.

Pete

[Guest Trace]

I believe if the dimentions given, 3/4" x 2", mortise and tenon joints would work. However, using the rule of thirds, leaves little room for error. M & T work better for me if the tennon can be at least 3/8" thick. In 3/4" material that leaves 3/16" on each side of the tenon. I"m a big half lap fan.