I am making two bedside tables and all is going well for this novice. But with no experience to go on, how much "play" is allowed in a glue joint? My dado is 1/4" wide and some tenons are very close to this and I would assume acceptable, given film thickness of the glue. Some other tenons have "play" due to their being 3/16". Maybe a fraction less than that. (I know where I went wrong on the cutting of the tenons-impatience!) Can I place a shim in the space when I glue up? Is this strong? Or do I need to recut and get precisely the right size? I can easily fit shims in the space but don't know the long term implications. Thanks for this and all future help! Frank
I think you can install shims and come out with an acceptable joint. Make sure everything gets a full coat of glue. The adhesives today are very strong and as long as you do not have large voids, it should work fine. Make sure you don't "over correct" and make the joint too tight with a shim and risk splitting it out.
I try to get my mortise and tenon joints so I can get them together by hand or with GENTLE tapping with a mallet. I don't want them to fall together, nor have to be driven in place. It takes a litle practice, but is pretty easy to do.
I have a story on my site (see the link below) that describes how I go about it. You may find a procedure that works better for you, but it seems everyone is pretty close on mkaing these joints.
Using a pc. of veneer is the standard way to repair a loose tendon. Use either a pc. of plain veneer (not with paper backing) of similar movement etc. specs. or resaw a pc. of your same material. Keep grain orinintation same. Can glue on one side to align tendon or both sides to keep alignment. Glue and clamp to tendon (w/ waxpaper & scrap) give a hour or so to set, then can sand or scrape to get a rightous fit. Rightous fit is one that has a somewhat snug friction fit. If you have to bang it in, it/s to tight, and will glue starve the joint.
Both of the prior answers were good for how to fix the problem.
To answer the question asked, a M&T joint needs to be a tight friction fit. Your should be able to fit them together and not have it fall apart by holding one of the parts in line with the joint. Todays glues are good but unless you use an epoxy you can't fill gaps.
This is in the category of "for what it's worth" info and we're relying on my memory (uh-oh) to get it right, but it seems to me that Rusty of Quick-Tenon fame did some research and for maximum strength the gap can't be much more than .003 inches. Now, if I'm wrong, don't blame Rusty, blame me. If somebody knows what I'm talking about, just jump in and correct me.
I have recently been useing Gorrilla glue which you can pick up at your local woodworking shop. And without question it is the best thing for filling voids. I have used it on mortise & tennon and it worked wonderfully regardless of how tight the joint was. Just take caution in how you clamp your project, and the glue will take care of the rest. And always follow the manufactures directions!!!
If you haven't access to veneer a trick I was shown many years ago was to use Cartridge Paper..I don't know if it's called that here but it's stiff Paper bordering thin cardboard.
Bear in mind that water based adhesives like Titebond will start to swell the wood so if you do have good joints then work quickly as clamping gets quite difficult if the joints are tightening up and the glue is hardening. Believe me I know....one day I'll tell you about a panel door a mallet and a policeman.!!
...and 1 more little trick to fix up a too-loose M&T joint.
I'm not the neatest woodworker on the block, and I like the look of a little sawdust on the floor, a nice little pile of wood chips in front of the jointer, and a few curls of shavings laying about. On occassion, I have used a fold or two of shaving to tighten up the gap. A dab of glue on both the tenon and the shaving will keep everything in place. Worked for me :)