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To get out in the weeds, I love surgical rubber tubing for clamping odd shapes. The farther you stretch it and the more wraps you apply, the tighter it squeezes.
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(03-30-2020, 09:38 AM)jteneyck Wrote: Epoxy is the only glue I'm aware of that fills gaps w/o losing strength. It also doesn't need nor really want much clamping pressure to create a high strength bond. Dowels often don't fill the holes well in joints being repaired and then you have trouble clamping the joint tightly, too. Double trouble for anything besides ...... yes, epoxy.
John
My experience does not bear this out. I had an old rocking chair that needed extensive repair. Most of the rungs fit the holes very very loosely. I used System Three T88 to put it all back together and all of the joints failed because the epoxy could not withstand the racking sideways forces typical of a rocking chair. Being very surprised and wondering if my mix was wrong or if I had a bad batch of glue, I did some tests with large dowels in over sized holes. For one, I used just the T88 and for the other, I used T88 mixed with sanding dust to the approx. consistency of peanut butter. After they cured, I put sideways racking pressure on both to the point of failure. The T88 only joint had glue failure and the dowel just levered out of the hole. The peanut butter mix held strong and the dowel broke off just above the hole. I re-glued the rocking chair using the peanut butter mix and it is still holding together with daily use.
I think that if your joint is only slightly loose, epoxy will work fine. However, if you can feel any side to side movement or if the hole is considerably tapered, then filler is needed.
During this process, I spoke with a System 3 rep and he said that T88 is a glue and not a filler. It is not intended to be used that way and he was not surprised by the failure. System 3 does. however, make a product for that purpose (can't remember what it is called but, you can find it on their web site.
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2 keys to working successfully with epoxy:
1) surface prep - make sure your surfaces are free of old glues, oily residue debris etc
2) Use of fillers to maintain a bond line thickness. If you clamp epoxy too hard, it will extrude out of the joint and starve it. Fillers help stop that. Wood dust works. Industrial users use glass beads, chopped fibers etc. I think for woodworking, almost anything clean would work.
Hot hide glue also has gap filling properties. Polyurethanes like Gorilla glue and PVAs like Tite Bond do not.
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(03-31-2020, 10:48 PM)Willyou Wrote: My experience does not bear this out. I had an old rocking chair that needed extensive repair. Most of the rungs fit the holes very very loosely. I used System Three T88 to put it all back together and all of the joints failed because the epoxy could not withstand the racking sideways forces typical of a rocking chair. Being very surprised and wondering if my mix was wrong or if I had a bad batch of glue, I did some tests with large dowels in over sized holes. For one, I used just the T88 and for the other, I used T88 mixed with sanding dust to the approx. consistency of peanut butter. After they cured, I put sideways racking pressure on both to the point of failure. The T88 only joint had glue failure and the dowel just levered out of the hole. The peanut butter mix held strong and the dowel broke off just above the hole. I re-glued the rocking chair using the peanut butter mix and it is still holding together with daily use.
I think that if your joint is only slightly loose, epoxy will work fine. However, if you can feel any side to side movement or if the hole is considerably tapered, then filler is needed.
During this process, I spoke with a System 3 rep and he said that T88 is a glue and not a filler. It is not intended to be used that way and he was not surprised by the failure. System 3 does. however, make a product for that purpose (can't remember what it is called but, you can find it on their web site.
Interesting results. I've never had an epoxy joint let go (I use T88, too); maybe none has gaps as large as you described. Anyway, good info.. Thanks.
John
