Adhesion problems - copper to wood w/ CA?

A

AndrewC

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Nov 14, 2017
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I've been making scales that go: Ebony "bolster" | 0.016" strip of copper | main wood scale -- all on a PVC/vinyl liner. I usually used to glue them up with epoxy -- G-flex or a long-cure BSI, say, on a G-10 liner, which worked great.

On the advice of the guys down at TruGrit, I started trying their PVC/vinyl liner material and the extra-thick Maxi-Cure 10-25 sec setup CA glue (the pink bottle), partly just due to time-savings. I was a little nervous, but I've got 3 6mm pins in the wood and a 3mm pin in the ebony for belt-and-suspenders so I felt OK about it. (Also I scuff up all surfaces and clean everything really well with acetone then EtOH.)

BUT the dang copper strip does not like to stick to the wood, if there's any flex before I get the scale on the blade. This wasn't a problem with the G-10 and epoxy, partly because the G-10 barely flexes and the vinyl does, and partly because of epoxy vs. CA under that kind of force. The Cu will stay stuck to one side/wood or the other, and I usually just wait until just before putting the scale on the knife and final glue-up and then get another drop of CA in there, press it tight, and glue it all up - I'm sure it's not going to separate laterally later! - but it just bugs me that I'm not getting a good bond in the first place, first time around.

Any thoughts?
 
Copper doesn't glue well to anything.

Rough the copper.
Rough the surface of the wood.
Use a slow cure epoxy. G-flex is a good choice.

Put two 1/16" or 3/64" pins through the copper into the ebony, and drill holes in the wood for the pins to go in. Epoxy will fill the holes and lock the bolster/copper/wood together.
The pin holes can be a little oversize to make fit-up easier, as the epoxy will fill everything.
That will solve your problem.
 
Double check but the PVC might not work well with the epoxy. I think that is why the OP was using CA. I was just looking at that stuff the other day and passed because I wasn't sure how to glue it.
 
Storm W said:
Double check but the PVC might not work well with the epoxy. I think that is why the OP was using CA. I was just looking at that stuff the other day and passed because I wasn't sure how to glue it.
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Nah, actually the TruGrit website listing for the PVC/vinyl (where I bought it) specifically says that it doesn't work well with epoxy and to use CA - in fact I was on the phone with their guy (Jeff?) just after last year's Blade and he sold me on the PVC and this specific CA for it.

It's the copper that's the issue. When I was using epoxy it stuck fairly well to the copper. I just hate to have to do a glue-up with CA and epoxy - that'll be a serious p.i.t.a. to try to wrangle with a 10-25 second drying time on the CA and get my epoxy in there too... and kind of negates all the advantage of time that's why I went to PVC and CA in the first place -- I might as well just go back to G-flex and G-10 if that's the case, sigh.

Although I like Stacy's idea of just sticking a pin or two through the copper into the ebony to keep it from flexing, at least off the ebony. I mean, the copper's not going anywhere in that case, and even if it does flex off the wood as I described, putting another drop in at the final glue-up will keep everything together without a gap going forward.

Thanks.
 
I’ve only had it stay together with pins. As the oxides form on the copper, the glue is left being stuck to the oxides, not the copper. You need a mechanical fastener.
 
I use G/Flex with cleaned and roughed up copper (or brass as in photo below) and pins.

MsMzCjU.jpg
 
My limited experience is if your using brass/copper separators (which I love the look) and plan on drilling it for lengthwise pins drill the metal first before gluing and re-flatten, the back side of the metal gets pushed out from the pressure of the bit blowing thru. If glued before drilling when the bit hits the back side and punches thru the metal the pieces like to come apart :eek:from the dimple on the back side. If there's any solution to prevent that I'd be obliged. As others have said rough up the metal (with a dremel?), use epoxy pins and whatever else to help improve adhesion. Can't speak to the PVC/vinyl/CA glue angle though.

I also fashion a pin template that really helps getting the alignment right between all the pieces. If using metal spacers drilled first then that piece can also serve as the template. Just don't be like John Cahoon John Cahoon and put the pins too low or too deep into the front piece when you have a pronounced finger choil :(.

That said I've been using jb weld for any metal/wood or metal/metal pieces cause of the 400 degree temp tolerance, seems to help when final shaping on machines and I've never had a heat separation event. For final scale to tang epoxy my go to is K&G's A+B house brand, by then my scales are 95% shaped and it's generally all hand work.
 
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Willie71 said:
I’ve only had it stay together with pins. As the oxides form on the copper, the glue is left being stuck to the oxides, not the copper. You need a mechanical fastener.
Click to expand...
Can you explain how that can happen on freshly sanded and coated with epoxy copper ?
 
As Stacy mentioned, copper is notoriously difficult to keep glued, particularly when grinding. In my experience the best adhesive for this application has been Loctite 324, sandblasting the copper also helped tremendously. Not sure how it would work with the PVC liner, I purchased some of that liner material several years back and then proceeded to throw it in the trash. I found G10 to be superior for liner material.

Blessings,
Joshua
 
I second Joshua. After testing, I threw the PVC material away and only use G10 now.
Tim
 
I missed that it was PVC. I would not use PVC as a knife handle part. Use thin G-10, or other fiber liner material.
 
Is the "High Tech Plastic Spacer" material that Texas Knife Supply sells also PVC?
 
Natlek said:
Can you explain how that can happen on freshly sanded and coated with epoxy copper ?
Click to expand...

From what I understand, the molecules thick layer forms very quickly, like fractions of a second, if not nanoseconds. This is similar to aluminum, titanium, and stainless. They need inert environments to weld, which is why we use flux for brazing, and tig or mig for welding. I don't know why copper is so much worse than the other two, which are a pain as well, but I suspect its because its soft.
 
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