tenon dimension

[unimog]

This may sound like a silly question.:dontknow:
Is there any rules to dimension a tenon? For example with a 2x4 how much material would you remove?
Thank you,
CHO

 

[gator]

There are always exceptions and special cases, but, the general rule-of-thumb is 1/3 of the material thickness. Some of the exceptions are for really thick material, you use a double tenon side by side (say for a 2" thick workpiece you could use 3/8" tenons with 1/2" between and 3/8" on each outside).

George

 

[cpowell]

This may sound like a silly question.:dontknow:
Is there any rules to dimension a tenon? For example with a 2x4 how much material would you remove?
Thank you,
CHO

It's not a silly question at all. You can find rule of thumbs for M&T dimensions by Google (I don't remember all of them off the top of my head. Here's a link to one source http://www.geoffswoodwork.co.uk/mortise01.htm

In your case if you're talking about BORG 2x4s (1.5 x 3.5 inch stock) I'd use a tenon 3/8 thick, 2 1/2 wide, 2 1/2 long...doesn't match the rule of thumb but 3/8 is plenty thick for 1.5 inch thick stock.

There are other factors that depend on the joint location and what type of forces would the joint need to withstand.


Chuck

 

[Gregory Paolini]

Ahhh... A subject of some debate...

BUT, the general rules are that tennon thickness should be 1/3 to 1/2 of the stock thickness. There are some things you'll have to consider though - Like how big the porportions of the mortise will be. You don't want to leave your mortises with walls that are so thin that they create a weak link.

Tennon width is usually limited to about 4". You don't really want to go bigger than that, because of expansion/contraction issues - Again, there are exceptions, but these are the general rules.

Tennon length can vary quite a bit. In the 2x4 scenario, If I were makeing a door or a frame, I'd make the tennons 2" long, or more. The longer the better. If I need even more strength, I'll cut a through mortise, and wedge into the ends of the tennon (3 1/2"long tennon), locking everything together.

Hope this helps!

 

[unimog]

The explanations do make sense now.

Thank you for the help.:eusa_clap
CHO

 

[Gofor]

Thickness of 1/3 to 1/2 is a good rule, with 1/3 the norm. However, on width, the location of the mortise is a factor. If the mortise is toward the end of a board, you want at least the board thickness from the end for the mortise on hardwood, and more (up to twice) for soft wood like pine. This may call for a "haunched" tenon, depending on how you are using it.

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