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Tom Henderson2
08-06-2010, 3:15 PM
Gents-

I'm new to hand-cut M&T joints, so I have a lot to learn.

If I pooch a tenon, I can glue the offcut back on and try again.

What options do I have if the tenon is chopped at a slight angle?

I was delighted at how well my first hand-cut tenon fit into my first hand-chopped mortise; just a few minutes with a router plane and it fit quite nicely into the mortise.

Unfortunately, the mortise isn't quite square which will give me trouble when I go to assemble the piece. I didn't measure the angle but it is enough to be quite obvious at first glance.

One option is to undercut one side of the mortise until the stretcher fits square to the leg. That means I'll probably only get glue contact on that one side of the tenon, but at least it will all be square.

Any other suggestions? I'm hoping I don't have to throw the leg away and start over....

-Tom in Ventura

john brenton
08-06-2010, 3:27 PM
Shims.

Pooched...I like that.


Gents-

I'm new to hand-cut M&T joints, so I have a lot to learn.

If I pooch a tenon, I can glue the offcut back on and try again.

What options do I have if the tenon is chopped at a slight angle?

I was delighted at how well my first hand-cut tenon fit into my first hand-chopped mortise; just a few minutes with a router plane and it fit quite nicely into the mortise.

Unfortunately, the mortise isn't quite square which will give me trouble when I go to assemble the piece. I didn't measure the angle but it is enough to be quite obvious at first glance.

One option is to undercut one side of the mortise until the stretcher fits square to the leg. That means I'll probably only get glue contact on that one side of the tenon, but at least it will all be square.

Any other suggestions? I'm hoping I don't have to throw the leg away and start over....

-Tom in Ventura

David Weaver
08-06-2010, 3:50 PM
Suggestion to make the mortise straight - either set something up in your field of view while you're chopping the mortise, or paint a line on the wall, or stick tape to it, to line up your mortise chisel until you get used to feeling what vertical is.

Of course assuming that backside of the sticking or whatever you're working on is square so that the piece sits vertical.

lowell holmes
08-06-2010, 3:55 PM
I would straighten the walls of the mortice and then glue veneers onto the corresponding tenon sides. I've repaired m&t joints in the past. :)

Sean Hughto
08-06-2010, 3:59 PM
If your part is still oversized, you could slice off the slanted mortise bit and try again by chopping a new mortise. If you have to use the piece you've got, I'd cut a small oversized slice that I could glue to the offending wall, and after it dries, cut that wall again, but straight this time (the other wall likely will need some tweaking too so that the two are parallel.

Tom Henderson2
08-06-2010, 11:09 PM
Thanks everyone; I'll have to think about this a bit.

-Tom in Ventura

Derek Cohen
08-07-2010, 9:22 AM
I am not clear if the tenon or mortice is out-of-square, or both?

To straighten a tenon, use a router plane. It this causes it to be too thin, glue on a shim.

If the mortice is the offending item, either widen it, or fill it in with a wooden plug and redo it.

Regards from Perth

Derek

Russell Sansom
08-07-2010, 11:33 AM
For most MT joints ( ones with shoulders ), it's the shoulders that square the joint while the tenon locates the perpendicular member on the face of the other. If the shoulders aren't square, you have to start over or shorten up the rails by cutting new shoulders. Some projects might allow this. If the location isn't correct, you have to trim or shim the tenon (or trim the mortise) until it is. Since tenons are all side grain, shims glue on easily and shouldn't compromise the joint.

In my view of things, the tenon's job is to keep the joint from wiggling and to give you something to connect to for pulling the two boards together.
To state the obvious, getting all this right rarely occurs by accident. As a beginner, you should mark the joints out with great precision. "perfectly" is a better word. Shoulders lines must be cut with a knife. If your lines are perfect, everything else is almost anti-climactic.

Terry Beadle
08-07-2010, 11:45 AM
Don't forget wedges in an tennon. Either a fox wedge or a slip wedge will work to make a too thin tennon wider with out having to wait for a glued shim to dry. Wedges can also widen the too short tennon length wise.

Also, I usually saw the tennon just a tad over sized so that the hand router can do the final square to surface cutting. That being said, learning to saw to the line ( or split it ) is key.

harry strasil
08-07-2010, 11:56 AM
"What options do I have if the tenon is chopped at a slight angle?"

I believe you mean the mortice at a slight angle!

The easiest way is to determine the angle then glue a piece onto the tenon and make the tenon the same angle as the Mortice. It's the least time consuming method.

make a dummy tenon, stick it in the mortice then clamp a narrow scrap to the outside of the morticed piece and another scrap to it so that you can place the jig along the tenoned piece to get the right angle, then work the other side of the tenon down so it's the proper thickness. not all that difficult to do.

I spent a bit of time in Ventura in the early 60's while I was stationed at Port Hueneme.