Fill small gaps in mortise and tenon joints?

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Forum topic by Chuck1856 posted 06-23-2009 02:31 AM 9273 views 0 times favorited 6 replies Add to Favorites Watch
View Chuck1856's profile


2 posts in 4230 days

06-23-2009 02:31 AM

Topic tags/keywords: gaps filling joinery mortise and tenon

Hi all,

A long time back I started a very basic wall mirror project, then promptly had a kid and left the thing collecting dust for a couple years! Well, I’m picking it up and have a question before I proceed.

I had already glued up the main sides and top/bottom pieces, using blind mortise and tenon joinery. It was my first attempt and generally OK but I do have some small gaps between the shoulders of the tenons and the face of the edge of the mating component. They’re on the surface, not on all joints, and probably ~1/16” or less.

Anyways, I’m ready for final sanding and staining and trying to figure what to do with these. I could just leave them but I think it might be better to fill and stain them. Any recommendations on doing this and how to do so? What should I used to do that..some type of putty?


6 replies so far

View poroskywood's profile


618 posts in 3818 days

#1 posted 06-23-2009 02:57 AM

Hey Chuck, I’m a fan of cutting thin slices of the same wood, wedging them in the gap with a finger of glue and sanding dust also from the same material. Pack it full and tight and sand smooth. Also I may be completely wrong and this might not be good advice, although I do it often. It seems to work for me. Putty will shrink and crack yuk, Famowood might be a good alternative however.

-- There's many a slip betwixt a cup and a lip.--Scott

View rwyoung's profile


412 posts in 3926 days

#2 posted 06-23-2009 03:23 AM

How do you feel about shortening the tennon just a little bit then cut back a fresh edge on the shoulder ending up with the original length of tennon on each end but a bit shorter finished dimension in the frame.

You could use a shoulder plane to pare back a bit of shoulder or chisel (try back beveling the shoulder a bit). Either is a good excuse for a new tool (toy), new plane or chisels or water stones, etc. ;)

Wait, scratch that. Short term memory loss, I read that you already glued it up but it didn’t process until after I entered my response. Sorry. The sliver of wood + glue + sawdust might be your best option. Dilute the glue down say 1 part glue to 3 or 4 parts water so you it has a better chance of taking stain. The line might be a little bit visible though because the sliver and dust will take stain differently than the surrounding wood.

And yet another option that occurs to me, you could kerf the joint and inlay a contrasting wood. The old “if you can’t hide it, accentuate it” trick.

-- Don't sweat the petty things and don't pet the sweaty things.

View davidroberts's profile


1027 posts in 3940 days

#3 posted 06-23-2009 03:49 AM

I’m not a big putty fan. Putty does not stain well. If the gaps are too noticable for your comfort level (been there, done that), you may consider sanding with a bit cyanoacrylate glue at the joint gap. A site describing this method better than me is shown below. Scroll down to CA as Filler. Another method is to use a gel stain. Just scrap some across the gaps then rub across the surface. Some of the gel should stay in the gap and dry. But you have to be careful with the color blending. You can find most any shade of gel stain at Rocklers or Woodcraft, or other online sources.

-- Better woodworking through old hand tools.

View BTKS's profile


1989 posts in 3918 days

#4 posted 06-25-2009 06:01 AM

I prefer the glue mixed with sawdust of the same wood. It’s worked for me and is as easy as it gets. I just put a glob of glue in my palm, mix in sawdust (amazing how much it takes) until it takes on the consistency of putty then rub it into the crevace. It will take stain, not perfect but better than a gap. Best of luck, BTKS

-- "Man's ingenuity has outrun his intelligence" (Joseph Wood Krutch)

View Kent Shepherd's profile

Kent Shepherd

2718 posts in 3740 days

#5 posted 06-25-2009 06:44 PM

I think that poroskywood was right on. That’s what I would do. And Famowood is good as well as Fix Wood
Patch, whichever is available to you. I guess you already figured out that time spent on the joint before glue-up is well worth it., but there are always ways to compensate after the fact. good luck with your project.


View SnowyRiver's profile


51458 posts in 3934 days

#6 posted 06-25-2009 06:44 PM

I use sawdust from the wood you are using, and polyurethane glue. Mix it together, thick, and pack the joint. Dont over pack as the glue will expand when drying. Then sand it and stain it. Poly takes stain well. Done right, you cant see the seam.

-- Wayne - Plymouth MN

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