Reply by coloradoclimber

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Posted on Question: how do you glue / epoxy knife scales on ? Mine fell off

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548 posts in 4309 days

#1 posted 12-30-2009 08:57 AM

Mark, thanks for the PM. And thanks everyone else for the suggestions.

I’m leaning toward some / all of the fault being mine.

I decided to do a little more research now that 6 of the 8 scales have failed. I looked into getting some West System but the only place around here that has it is Rocker which is 50 miles away, each way, and only has it in quart sizes, so I end up with a half gallon of epoxy at $85 USD. Too far away, too much epoxy, too much money.

Woodcraft carries a product called T-88 Structural Epoxy Adhesive by System Three. Woodcraft is 12 miles away, has it in a half pint size, and it costs $17.50 USD. All three a better fit for me.

System Three has a free PDF book called appropriately The Epoxy Book. In the section on techniques of epoxy use they have a bullet point:

“Third, do not over-clamp. Epoxy resins require only contact pressure.
Over-clamping can squeeze most of the adhesive out of the
glue joint and the epoxy that is left is absorbed into the wood
starving the joint. A glue-starved joint is very weak. Use only
enough pressure to hold the joint immobile and keep the two
surfaces in contact until the epoxy has set overnight at normal
temperatures. Nails, screws, clamps, rubber bands, or staples can
all be utilized.. Clamp just hard enough to close up the joint.”

And as I state above. I OVER CLAMPED the scales pretty hard. I put 3 Jorgensen bar clamps per handle, 3 was about all I could fit, and I CRANKED them down, hard. I was going for a near invisible handle to tang glue joint and I got it. The joint was paper thin or less. Pretty much you couldn’t even see the glue joint before the scales popped off. That’s how I cold tell the other scales were going bad. I could see a hairline joint at the scale to tang surface.

So at this point I’m willing to believe some (or most) of the fault lies with me. I’ll be trying again tomorrow with the following procedure:

- Rough the tangs a bit more aggressively. Maybe hit them a stoke or two with a bench grinder, or maybe just a bit more aggressive on some 100 grit sandpaper.
- Dremel some shallow grooves in the back sides of the scales to hold a bit more epoxy.
- Rough up the scales on some 100 grit sand paper.
- Wash both the scale and tang with acetone.
- Use better epoxy.
- Clamp the much more gently.

And we’ll see what round two brings. I’ll update on the success or failure of this new attempt.

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