Please give me you thoughts on this M&T joint

[jonathan snyder]

Hi Folks,

Let me preface this by saying I am probably in way over my head. I am attempting to build a small two drawer end table. Perhaps something similar to what Martin S. posted a while back. I have never designed a table before, let alone built one! Attached is a picture of the joint I cut to attach the side aprons to the front legs.

I hoped to account for seasonal movement by breaking the tenons into two. They are sized the way they are to accommodate the double mortises for the front drawer dividers. I haunched both tenons and kept a stub in the middle to prevent twist.

I plan to glue only the top tenon, using System 3 epoxy. Will that be adequate? I am also thinking about hard maple pins, two per tenon, for strength as much as decoration. What do you think?

Any advise as to how this should have been done would be appreciated!

Thanks
Jonathan

51886

[Mike Cutler]

Jonathan. Tricky little joint you have going there.
First, You are correct. It's too wide to glue all at once. Gluing the top mortise should be fine, But I would drawbore the pins into the joint. I probably would be inclined to glue the bottom mortise actually because it's only 3" wide,but I think it's the top one that you cannot have movemant on, due to other design factors. Is this correct?
I would use one pin for the top, and two for the bottom mortise, Elongating the two holes for the bottom mortise to allow for movement.
One question though. Why is the mortise haunched at an angle, instead of using the shoulder of the haunch as a support?

[jonathan snyder]

Mike,

Thanks for your thoughts. I guess I can't have any movement at the top tenon due to the tabletop. I'm not sure wht you mean by drawbore. Can you please explain. I understand I need to elongate the pin holes on the bottom tenon, but by how much. I haunched the tenons at an angle, because I read an article in FWW by Garrett Hack on building a table, and thats how he dit it. Would you have cut the haunch straight across? Why?

As I said I'm in way over my head, its my first table, heck its my first try at complicated joinery.

Thanks
Jonathan

Looking forward to hearing other folks thoughts.

[Greg Robbins]

I've built quite a few Queen Anne pieces and have used the double tenon method. I've never put a dado between the mortises like you did, as I don't think it's necessary. The tenons themselves are large enough to keep things stable. I glue the tenons as I would any tenon and have never had any problem with wood movement. I'm not sure why you would use epoxy, as any of the titebond glues are more than sufficient for strength. The pins are not necessay for strength. If you like them for looks then I say go for it. I personally don't like the looks of pinned tenons. But that's just me.

Regards Greg

[Neil Lamens]

Hey Jonathan:

Being in your seasonal extreme conditions, its understandable you are concerned about movement.

Don't over think this.............you are well on your way to a successful build, your machining is an indication of your thoughtfulness.

Go for it, man...........you're on your way.

[Mike Cutler]

Jonathan. I probably would have just cut the shoulders straight, but I wouldn't argue with Garret Hack. He's built more fine furniture than I ever will. If that is his method, I'm certain it will work just fine.

"Drawbore" . This is method of utilizing the pin to "draw" the joint together. A hole, or holes are drilled into the tenon. Then holes are drilled into the mortised section that are just slightly off from the tenon hole farther from the joint edge, 1/64" to 1/32" is good for hardwoods, when the pin is inserted it pulls the tenon into the mortise.
The pin does not have to go all the way through. it can be done blind. It just has to go through the mortise.

I like the System 3 epoxies. I use them almost exclusively. I really like having the extended open time available for large glueups. It relieves a lot of mental pressure. Epoxy the top, pin the bottom and you should be fine.

At 7+ inches of total mortise I would be concerned about wood movement also. The purpose of dividing the tenon. and haunching it is to decrease the stress that a single 7+" tenon could exert on a mortised member if it were to cup. It's a fine joint.

[Martin Shupe]

Johnathan,

Listen to Mike C., he has explained it very well.

FWIW, I used this same technique, but didn't drawbore the bottom pin, which I now regret. A very tiny bit of separation has developed in my joint between the leg and rail. My wife doesn't care, but I do.:( If I had drawbored, I wouldn't have the separation.

The folks at Popular Woodworking have a sister publication called, Woodworking Magazine. It is only published two times per year, and only available on the newstand. Look for it, it is well worth it. They had a nice article on drawboring a while back.

http://www.woodworking-magazine.com/blog/SearchView.aspx?q=drawboring

Follow the above link for more information on their blog. Be sure to scroll down all the way, as I did a search on drawboring, and several articles came up.

Be sure to post a pic of your table when you are done. Judging from your attention to detail, I am sure it will turn out fantastic.

[Steve Schoene]

Just a few thoughts. I am a bit troubled by the taper or slope on the top and bottom tenon hanches. Unless they don't bottom on the mortise, won't they act as wedges to open the joint if the rail swells in width?

I wouldn't think that pins are needed, except for aesthetic reasons. And, if you are worried about seasonal changes, elongate the pin hole--in the mortise only, on the unglued tenon.

Personally, I'd stay with a PVA, or Hide glue. Epoxy can be pretty messy, and darned hard to get out of pores if you misjudge the squeeze out. Besides I don't like the smell in doors, and particularly don't like the smell of the acetone needed to clean off squeeze out.

[jonathan snyder]

Thanks for everyones advise, lots to digest here.

Mike, Thanks for the explanation of draw-boring, sounds like it might be a bit tricky to get just the right offset on the holes. I'll play around with some scrap first.

Greg, I have never built a table before. I included the stub tenon in the center, following a couple of FWW articles. It was suggested it would discourage twist. I guess it can't hurt.

Neil, Thanks for the encouragement!

Martin, The two drawer table you posted a while back, was the inspiration for this. Thanks. I'm off to look for woodworking magazine!

Steve, Good point about the sloped haunch. I will make sure it does not bottom out in the mortise. I took that design from a Garrett Hack article, maybe blind faith is a bad thing! I did not question the design. This is all very new to me.

I choose to try the epoxy for several reasons. I understand it has better gap filling properties and longer open time than PVA. This is only the second project for me involving M&T's and I have already taken a hair too much off one of the tenon cheeks, so it does not fit as tight as I would like, so I think epoxy will be a better choice. Having never done a glue up like this before, I think the longer open time will be advantageous.

Thanks Again
Jonathan

[Jim Becker]

Jonathan, I actually like the stub tenon between the larger tenons for the reason that you included them. It does make for more work, but it sure can't hurt the structure to include them. You'll see that on many breadboard edge designs, too, to keep things "flat" without binding.

[Don Henthorn Smithville, TX]

Jonathon, if one joint is a little loose glue on a piece of matching (same type wood) veneer and refit the joint. Then you won't have to use epoxy as glue. My personal feeling is that epoxy is not a good choice for furniture glue.

[Tim Sproul]

I would avoid drawboring, in the classic sense.

Drawboring, when done as Chris Schwartz describes in Woodworking Magazine, will be no different than gluing the bottom mortise and tenon. If you pin the bottom mortise and tenon and elongate the pin hole in the tenon (elongate the hole across the grain, not with the grain), then you've got expansion/contraction covered.

When I've faced mortise and tenons on wide pieces, I treat them like a breadboard. Fixe the joint in one spot (4 - 6 inches is about the widest) and then allow the remaining joint to slide crossgrain.

Is the mortise for the haunches ramped to match the shape of the haunches? If so...and the fit is tight, then you've set yourself up to have the tenons get pulled out of the mortises as the tenoned pieces expands.