2

A close friend called me for help with a busted chair leg. I hadn't seen it, but figured I'd probably be considering a good wood glue and some dowels inserted in angled holes to reinforce the thing.

As it turns out, the leg actually cracked approx 2-3 inches from the end, right beneath the corner block that attaches it to the seat. The end is about two inches square, and it appears to have given way right near where a large screw was inserted -- AND there's a knot just opposite the screw. The end is more narrow than the rest of the leg.

I'm not getting the sense that glue-and-dowels is going to be the right approach. This isn't high-end furniture. Are there cost-effective approaches to repairing and reinforcing this (to actually bear weight) without an entire workshop at my disposal? Thanks in advance.

Photos: This

And

this.

  • 1
    Is it feasible to just do another leg altogether? – Maxime Morin Jul 8 '17 at 0:02
  • Ugh! Sort of looking like that's what's needed. – Xavier J Jul 8 '17 at 0:26
  • 1
    This is fixable for sure, but to me it looks irreparable in a neat and tidy way. The best repair I think would be to drill for a central dowel and then glue everything together using thickened epoxy. Drilling the holes would be difficult to do perfectly so best to do it oversize and let the epoxy take care of the inevitable sloppy fit. But there are no guarantees about how strong the leg would end up. Worth trying? You could test for strength in about 2-3 days and go from there. – Graphus Jul 8 '17 at 8:23
  • The large screw does not appear to have any function (other than to weaken the leg...?) – Ecnerwal Jul 8 '17 at 14:11
  • @Ecnerwal I noticed that, too. I have to take another look, maybe at one of the other legs, to figure out what's going on there. – Xavier J Jul 8 '17 at 14:18
1

Looks like there's a pretty-good chance of a nice fit on the broken surfaces - Might try gluing the parts together on the break, wait for glue to dry, then drill from end for dowel and glue that in. The fact that it's so close to the end makes that practical to consider.

  • Good idea, clamping will probably be the challenge here. – Maxime Morin Jul 8 '17 at 16:01
  • Good idea in principle but it can be tricky to drill deeply into end grain and stay on course. – Graphus Jul 8 '17 at 21:38
  • @Graphus: the dowel doesnt really need to go all the way through the leg length. I think just getting 2-3 inches on either side of the break should be fine if the glue joint is even mediocre. – jbord39 Jul 9 '17 at 18:14
  • 1
    @jbord39 Yep, only a couple of inches should do. But that means having to go about 5 inches into end grain. This isn't at all impossible of course, but some guidance on how to do it (bit types to favour and ones to avoid, use of a jig to keep square etc.) plus any additional tips for this situation specifically (e.g. clamps applied externally to reduce chance of splitting) would make for a much more comprehensive Answer. – Graphus Jul 11 '17 at 5:20
1

This can be salvaged easily. Use epoxy - it will create a bond stronger than the wood. In this case, you are to use glue to overcome the structural weakness of the wood itself and epoxy excels at that.

You will need two part 5 minute epoxy (I suggest transparent instead of colored epoxy), clamps, scrap wood to protect the chair leg from the clamps. From the pictures given, it looks a like a clean break with a good surface and it is clampable - with a long clamp making contact at the chair leg top (the part that normally points to the ceiling) and the chair leg bottom (the part that normally is touching the ground).

Remove the hardware. Test fit the two parts, removing any bent bits or broken bits - you want the parts to fit together fully. Also test how your clamping will work, so you can adjust before you are 'on the clock' with mixed epoxy.

Mix the 5 minute epoxy in equal parts (as per the directions). Then apply, attempting to cover the interior surfaces while avoiding the opening for the hardware and avoiding the exterior edges. Then clamp the pieces together firmly. The firmness of the clamping is important to the strength of the joint and keeps the leg in the correct shape. If your test fitting, didn't work, a second clamp across the short side of the leg will help.

If the epoxy drips into the channel for the hardware: You can unclamp the leg, open the joint, wipe the channel clean, and reclamp. When lazy, I have used a small carving gouge to remove the extra epoxy when it starts to harden, instead of unclamping.

Since the outside of the leg has a smooth finish, if some of the epoxy bleeds out during clamping, my advice is to leave it. A small blob of epoxy is easier to remove than a smear of epoxy. On unfinished wood, the epoxy leaves the wood looking 'wet' with a glossy surface. Be advised: the epoxy can remove some or all of a finish under the blob when popped off.

While the epoxy claims five minutes to set, there is some variation depending on mixing, age of the product, etc. Also the full bonding of the epoxy takes a much longer time to set fully, so just leave it clamped up for a while longer - a few hours or so. Reassemble the chair normally. The repair will be visible as a hairline fracture.

  • 5
    "Normally for joins, you want a glue weaker than the wood" Er, what? Even if this is what was desirable almost all glues currently in use create a bond stronger than the wood around them, as test after test confirms. – Graphus Dec 11 '18 at 6:51
  • Poor wording on my part: 'instead you want a glue that fails before the wood breaks'. While the details of glue mechanics is beyond the scope, the US Gov't has done a fair amount of work on the topic. fpl.fs.fed.us/documnts/fplgtr/fpl_gtr190.pdf See chaps. 5, 10-12 Also srs.fs.usda.gov/pubs/gtr/gtr_so071.pdf – ewm Dec 12 '18 at 0:44
  • That's exactly the same meaning in different words and like I said, you don't get that (and don't want, usually). When tests to failure are done on properly made glue joints the break occurs in the wood, with NO involvement of the glue line — study of the broken surfaces show that the crack will often pass right through the glue line like it's not even present. This is precisely what is desired in almost all woodworking applications (some joints in lutherie being an exception, kumiko work possibly also but that's just a guess). – Graphus Dec 12 '18 at 7:59
  • In the tradition I trained, joints are designed to be un-done. I don't want a tenon to shear but to leave the mortise intact, allowing for the joint be reglued instead of replicating a new part. I realize that my approach is the not same as others and have removed the offending sentence. Apologies for the fuss. – ewm Dec 12 '18 at 16:03
  • Yeah I was puzzled by this as well. Only when I still did amateur luthier work did we ever consider weaker glues, and only for very specific applications. Most joints where considered permanent, and the fact that the material would shear before the joint did was considered a feature. – jdv Dec 12 '18 at 17:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.