Shimming a loose fitting tenon?

[Anthony Watson]

I made my first mortise and tenon joints yesterday for a small dining table I'm building. I cut the mortises with a forstner bit in my drill press, and cut the tenons on my tablesaw by "nibbling" away the wood. I made several test pieces and had everything fine tuned perfectly for a nice snug fit. So, I braved the actual mortises and tenons for my project.

I'm not sure where I messed up, but the final tenons seem a bit loose in the mortises. Not by much, but with no experience in this area, I would think they should fit tighter. The tenon pushes in easily by hand, but won't always stay in the joint if I pick the piece up.

I would estimate the "slop" is the thickness of a piece of paper, which has me wondering... Could I glue a piece of paper (or an index card) to the tenon to shim it to the proper thickness, or would a paper shim be too weak? I've seen recommendations to glue a wood veneer, but I don't have any of that around.

So, how tight should the tenon fit the mortise, and what can I use to shim tenons assuming they're too loose?

Thanks,

Anthony

[Michael McCoy]

I wouldn't use paper but I have glued wood on a tenon and milled the tenons again. Just match grain direction.

[Brian D Anderson]

I just had a similar problem. Though I was using loose tenons, so I ended up creating new tenon stock. My problem was that my mortises in each piece were slightly different thicknesses. So I made my tenon the thickness of the widest mortise and used my stationary belt sander to fine tune the other half of the tenon.

Anyway, all of that is completely useless for you :) As suggested, gluing more wood on seems like it would work.

-Brian

[Lee Schierer]

I'm not sure I would recommend paper either. Making a .003"-.004" thick shim from wood to exactly fit your tenon will be challenging. What I have done is glue another thicker piece to the tenon and then recut that side. That way you end up with a perfect fit. You can also set a hand plane and cut a shaving and glue it to the tenon. A sharp hand plane can easily make a shaving .001" to .003" thick.

Regarding fit. The pieces should slip together, not have to be pounded to get them tight, but should stay in place and not be so loose as to fall out. The glue is going to fill a certain amount of the gap without weakening the joint and will also swell the wood slightly so a paper thickness might not be too loose.

[Steve Kolbe]

couldn't you also notch the tenon and create a "keyed" or "wedged" tenon to take up that little bit of thickness?

[Joe Scharle]

Sometimes a shaving from your hand plane, glued on is enough. When I was still making tenons on my TS I fixed a few that way.

[Michael Faurot]

You could draw bore the tenon, which will then hold it tight into the mortise. When doing this, it's actually advantageous for the tenon to fit a bit loosely to start.

Info on draw boring can be found here (http://www.greenwoodworking.com/Drawbored%20M&T%20Joint.htm). Christopher Shwarz explains how to do this in his video Forgotten Hand Tools (http://www.woodcraft.com/family.aspx?familyid=20007&mode=videos).

[James Stokes]

I have used a fine grit sand paper an glued that on. Worked fine.

[Mike Henderson]

Others have given you some good suggestions. My suggestion has to do with cutting the tenons. I prefer to cut my tenons a bit "fat" and trim them to size. A shoulder plane, a chisel, or a block plane and chisel all work to do the trimming. It's bit more work to do it that way but it avoids the problem you encountered.

Good luck!

Mike

[Chris Padilla]

I'm not sure where I messed up, but the final tenons seem a bit loose in the mortises. Not by much, but with no experience in this area, I would think they should fit tighter. The tenon pushes in easily by hand, but won't always stay in the joint if I pick the piece up.

I'm betting that they are tight enough and that you should just glue 'em up. The glue will swell the wood unless you use epoxy. Epoxy might be a consideration if you feel the wood is too loose. It fill gaps extremely well.

Or, make another tenon slightly tighter, glue it in the mortise, and start all over.

[Alan Tolchinsky]

If you have any around, just use veneer or a shaving from a hand plane works great. I make my loose tenons a little fat and sand them down either with a belt sander or just loose sand paper.

[Brad Patch]

If you use a hammer the joint is too tight.

If you use your hat its too loose.

The joint should go together snugly and not come a apart all by itself.

Loose joints happen frequently, I usually cut a loose tennon marginally smaller and glue on a shim and re cut to the correct size.

[Curt Harms]

I saw someone use paper to shim a tenon on TV. I thought to myself ya know turners use paper joints to create joints that fail easily when turning mirror image turnings. I didn't know the goal of a mortise & tenon joint was to have it fail easily.

[Mike Cutler]

Sometimes a shaving from your hand plane, glued on is enough. When I was still making tenons on my TS I fixed a few that way.


How come I never thought, or heard of this fix before?:confused:
I really like this solution.:),;)

Thank you for sharing it with us Joe.

[glenn bradley]

I save the cutoffs from my tenon cheeks. If I goof up, I glue one back on and re-cut. Once assembled, they're scrap.

[Anthony Watson]

I glued some thin scraps onto the tenons and will remill them tomorrow. Hopefully things will go smoother the second time around...

Thanks for the suggestions!

Anthony

[Anthony Watson]

I recut the shimmed tenons today and now they fit perfectly. Thanks for the suggestions everyone!

Now on to assembly and finishing...

Anthony

[Stan Smith]

I save the cutoffs from my tenon cheeks. If I goof up, I glue one back on and re-cut. Once assembled, they're scrap.

A very practical way to go since you've just cut some. I've mixed some sawdust with some glue to help fill on a few occasions. Not sure if this is the best method to use though.

[Doug Shepard]

Sometimes a shaving from your hand plane, glued on is enough. When I was still making tenons on my TS I fixed a few that way.

Ditto. I've done a number of them that way. The only hard part is getting the shaving thick enough it doesn't want to disintegrate while you're trying to glue it on, and flattening the curl out of it without it breaking.

[Chris Padilla]

I screwed up cutting a mortise with my domino once. I just glued in a domino, trimmed it, recut the new mortise.

[Joe Cunningham]

Sometimes a shaving from your hand plane, glued on is enough. When I was still making tenons on my TS I fixed a few that way.

Used that on my last project. Worked great. I let it sit over night after rubbing it with a flat piece of wood, then trimmed off the excess with a sharp chisel.