Use of glue in a drawbore mortise and tenon joint
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If you use the drawbored method to pull together the mortise and tenon joint, do you need to use glue on the shoulders of the tenon and inside the mortise?
For that matter, do you need glue on the dowel? Seems if the dowel is hammered home it’s not likely to work itself loose.
Replies
I always use glue in the mortise, and on the tenon. I try really hard to keep glue off the shoulder. I put a little hide glue on the peg. It lubricates it a little and hels it slide into the hole.
A few years ago I made a small table using drawbore. Still love to point out that I used no glue on the piece.
If you examine the history of drawboring, such as it is, you'll notice that the great majority use no glue. But drawboring was used primarily for carpentry tasks such as building roofs and other large-scale wooden structures, where glue was replaced by joints that held together mechanically - which is what a drawbored M&T does.
One basic reason for using glue-less drawbored and other mechanical joints is to avoid the issue of a glued joint self-destructing when large moisture changes occur in the surrounding air, over weather and season cycles. The mechanical fixing allows differential expansion and contraction around the points at which the mechanical joint is handling the forces that try to pull it apart. (The pins in the M&T holes, in this case).
So, if you employ a drawbored M&T in a piece of fine furniture that's going to live in a modern house with minimal moisture changes, you could argue that glueing is a better method and the drawboring isn't needed other than maybe to help pull the joint firmly together as the glue dries - as a sort of clamp) ........ .
But the corollary is that if your M&T is less than perfect in it's precision (all tenon surfaces exactly fit all mortise surfaces) a drawbore pin or two will be the belt & braces that compensate for any imperfect or gappy glue joins. And, since drawboring makes glue redundant, why glue it at all?
Of course, you have to be precise in making the drawbores in the M&Ts - which M&Ts still need to fit without flop, rattle or glaring gaps.
I've never seen a mortise and tenon joint "self destruct" from changes in humidity.
Perhaps one day I'll take you on a tour of the farm gates of Cumbria; or those of West Wales, if you like. :-)
But no need to go all that way. Many second-hand shops and even museums have older furniture that's been subject to moisture changes big enough to pop the glue of M&T joints therein.
In our hoose, there are three Welsh chairs bought second (or possibly 7th) hand from local junk (I mean antique) shops in which nearly all the round M&Ts of the rails into the legs needed fettling. They'd been glued in rather than properly fitted wet/dry-but-tight with tangential rail-to-leg orientation.
Lataxe
Long story short, do what you want. Adding glue won't harm anything, it just adds an extra level of insurance should the joint change in size.
On a slightly different topic (but still applying to drawboring), be careful with how much you offset the drawbore. If you offset too much, you can put a lot of stress on the face of the rail with the mortice and can split the wood. I um, found this out the hard way. You only need a small offset and if done right can provide a pretty strong joint. If you foresee the need to disassemble the joint, you will probably be fine without glue, but glue can assure a tight, permanent joint.
See the attached photo, from Chris Schwarz’s The Anarchist’s Workbench https://blog.lostartpress.com/wp-content/uploads/2020/07/AWB_Consumer_June-2020_v5.pdf.
Building a workbench with big honkin' pegs that makes a ton of sense. I used brass rod for drawboring mine because the straightest grain pegs I could make were not getting it all the way through the 4" thickness before shattering.
On a normal furniture-scale project that needs a nice finish I'd avoid putting wax anywhere near it.
I would put glue everywhere. Can’t hurt and could help.
My grandfather told me that the earlier chair makers would make the seat of the chair from a green wood, the back and legs from dry wood. As the seat dried it would create a very strong joint. Can anyone verify that?
Hi Kbleiken, If you're going to go that far off topic please start a new thread. We like to make sure that you'll get the answers you're after, and also that it will be "findable" for anyone looking for the same info in the future. Sitting in a conversation about drawboring M&T joints your chairmaking Q will be lost forever.