Mortise/tenon size

[Ken Leshner]

Is there some rule-of-thumb for sizing the length, width and depth of a mortise/tenon?

[Ted Shrader]

Ken -

Generally I like to have the tenon thickness about half that of the piece of wood. ie ³/₈" tenon in a ¾" piece of wood. That leaves ³/₁₆" each for the shoulders. Also depends if you are using a mortiser with standard size chisels. Don't have one of those yet and end up using the drill press and finishing with a chisel. Either way keep the mortises to a "standard" size and tune the tenon to fit.

Now, how wide? That varies with where the corresponding mortise is in relation to the end of the piece of wood. In the middle of the piece, I just keep the shoulder the same all around the tenon (³/₁₆"). However, if it is at the end, make the shoulder at the end at least ½" or else no shoulder at all.

Length? Either through (or through and pinned) or at least 1" long (if blind) so you have plenty of long grain contact surface for gluing.

Regards,
Ted

[Mike Cutler]

Ken. There is a "general rule" that I learned long ago. I emphasize "general' because certain requirements of a joint will cause changes in the general rule.
The General Rule for M&T joints is "3x5x3". A tenon is 1/3 the thickness of the tenon stock. the tenon width is no greater than 5 times the tenon width, with a maximum tenon width of 3 inches ( wider tenons should be split to prevent joint failure. And the tenon length is 2/3 the width of the material the mortise is in.
Some joints may require more strength,ergo the tenon length and thickness will be greater, or a haunched tenon will be used.
Alot of people like to use a 3/8" tenon thickness in 3/4" material. nothing wrong here unless the joint will be exposed to stresses from the side.It also makes the marking and cutting the joint a little more familiar to people.
The oriental philosphy/practice for tenon length is to size the length of the tenon almost the entire width of the mortise stock.
As I stated before these are general rules. Nothing is etched in stone. I don't use these proportion all the time myself. my .02 fwiw

[Fred LeBail]

Ken, I make alot of Mortise & Tenon joints in my furniture peices.
All of my stock is 7/8 " and I make the mortises 3/8 " and everything is related to the face of the stock. My tenons are cut on an old Beaver table saw that is dedicated to cutting tenons. I have 2 sawblades and spacers and a sled (jig) set up to make these cuts. I cut 1/2 " shoulder on the tenons and these cuts are made on the table saw. The tenoning process takes 7 passes across a saw blade, to make all the cuts and I use this everyday with great ease and confidence that there is little sanding required.
I have some pics of this process that I will post if anyone is interested.
Fred

[Lamar Horton]

Fred, I would be very interested in seeing the pictures of your process, as I too make a lot of M&T joints and am always on the lok out for better and more efficient ways.

Lamar

[Norman Hitt]

Ken, I make alot of Mortise & Tenon joints in my furniture peices.
All of my stock is 7/8 " and I make the mortises 3/8 " and everything is related to the face of the stock. My tenons are cut on an old Beaver table saw that is dedicated to cutting tenons. I have 2 sawblades and spacers and a sled (jig) set up to make these cuts. I cut 1/2 " shoulder on the tenons and these cuts are made on the table saw. The tenoning process takes 7 passes across a saw blade, to make all the cuts and I use this everyday with great ease and confidence that there is little sanding required.
I have some pics of this process that I will post if anyone is interested.
Fred


Fred, I have used the exact same method you use for years, but you are the first person I have run across that does this. I mostly just used the two outside blades of a dado set, with spacers (usually 1/4" tenons though as my stock is mostly 3/4". I have also tried two sawblades but the results were not quite as good, because the blades I used weren't very good ones. Do you use Rip blades, on your setup, or what? I have an old (50's) craftsman contr saw that I plan to dedicate to that operation as soon as I get down that far on my "to do" list. Why don't you post some pics for the others.

I also had a router bit with two slot cutter blades spaced out to do the same thing for short tenons on small projects, but it has come up missing, and I can't seem to find another like it and don't know where it came from, as it was given to me by a friend that died a few years back. I think the cutters were 3 or 3 1/2" diameter and worked really well for small projects.

Cheers, and Saw Safe.........Norm

[Scott Parks]

Hmm, good Ideas. Maybe I'll keep my old C'man, just for tenoning.....

[Fred LeBail]

Fred, I would be very interested in seeing the pictures of your process, as I too make a lot of M&T joints and am always on the lok out for better and more efficient ways.

Lamar
Well guys I finally got the pics resized so hopefully they go through.
The first one shows the sled that I use to make the first cut.
#2. shows the actual cut being made.
#3. shows the first cut on the tablesaw with the jig to keep the tenon away from the fence. This helps keep the off cuts from getting jammed.
# 4. shows making the cheek cuts
# 5. shows making tha final cheek cuts with another jig
# 6. shows making the Mortises &
# 7 finally the finished product.
I'll send the rest
Fred

[Fred LeBail]

Fred, I would be very interested in seeing the pictures of your process, as I too make a lot of M&T joints and am always on the lok out for better and more efficient ways.

Lamar
Well here are the rest of the pics. Thanks for looking.
Fred