Wow! Lots of great responses. I'll summarize and respond, but first I
just recalled - with a Homer Simpson "doh!" forehead-slap - something from my past life that might be helpful - sorry that it's long.
In my latter waste-to-fuel venture company, I was designing a microreactor that required bonding high-temp inert tubing to high-temp ("pyrex"-type) glass - which is already a challenge, but guess what the tubing was?
Teflon. Everyone's heard of the ol'
"so how do they get Teflon to stick to the pan?". Basically, you don't. It isn't "stuck", it's "locked", mechanically. So we're sticking
Teflon to
glass - fun, huh? We were using a technique* from a team at Lehigh: the glass was etched with a diamond hole-saw, and the Teflon was
micro-'etched' with a funky fluoro- compound. That created a much larger, very ragged irregular surface area at the micro-level, "increasing bondability and co-efficient of friction" according to the FluoroEtch datasheet. We then used Duralco 4460 high-temp, low-viscosity, low-shrinkage epoxy from CoTronics. So, basically, the epoxy wasn't really so much "stuck" to the Teflon, as it was like having a too-small threaded bolt in a threaded hole, with a really sticky strong gap filler
locking them together. Key is obviously just surface roughness/surface area; also clean surface prep so there
was good bonding to the glass. Seems pretty analogous, now. So, that said, here're your thoughts & my responses.
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Glue Starvation. By far the most common suggestion.
Natlek, I liked your point about "just
try to squeeze all the glue out from 2 pieces of glass", although I
do think you can starve a joint somewhat (and
Chuck's from-the-horse's-mouth advice from West is useful, so might try measuring the thickness Δ for fun). Btw
Stacy, I'm using spring clamps from Home Depot ("Durabuilt") which are maybe stronger than HF's but don't seem to be getting a ton of squeezeout - I agree Jorgenson's or other screw clamps would be too much.
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Roughing/Properly Cleaning the G10. Yep,
Chip, Bill & Adam - I've done that, using a 60 grit and good pressure until I got a good scuffed surface. I think I'll try even more scuffing and try to expose a surface that's mostly fiberglass mat. I've seen suggestions elsewhere to drill some little holes through the G10 into the scales which seems helpful although I hope overkill 'cause that's lots of extra work (and risk of drill-through) and others don't seem to need to do it.... And yes I definitely do final cleanup with IPA, not acetone now - I know about the oily film**. Curious: does anyone have a strong opinion about "DN" vs. IPA? And by DN are we talking EtOH w/ a denaturant or MeOH (either meets the def'n at least in the lab). And if so do y'all use 70%, or Heet yellow (which is almost all MeOH btw), or what
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Choice of Epoxy Interesting.
Kevin, I could've sworn that BSI said their 15-min is the strongest (IIRC) and also most flexible, which seems like a good characteristic. Edit: just checked BSI site. 15-min is
most flexible, but 30-min is
strongest. It's also apparently better for metal/glass bonding; while 15-min is preferred for hardwood that's obviously less interesting. The 30-min has handle time of 8h and full-cure in 24h, vs 45m/2h for the 15m.
That said: I'm hearing a strong preference for West Systems G/Flex.
(Bill, thx for the pointer that it might be on sale - is that at the stores? I looked on the website, don't see a sale on it...?) It costs about 2x vs. BSI - but per-knife who cares about say 30¢...?
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Is it Really G10? Yep,
Jim, bought it from TruGrit, just double-checked my order for belt-and-suspenders, but good "are you sure it's plugged in?" thought.
My own add'l thoughts: I should re-make sure I'm really mixing it thoroughly, and in the right proportion. I
am using handle pins (plain, not Corby/Loveless), and this is for exotic-wood chefs' knives, not outdoor rough-use. I tend to believe that the pins make sure any shearing force can't get too strong, and it's hard to imagine any 'pulling' force on the scales let alone 'prying' action, so the epoxy ultimately shouldn't have much mechanical stress on it. As long as it's
fairly strong and stays adhered, and is waterproof -- and I tell my customers if they get their wood soaked, even though I do stabilize it, they're not only way out-of-warranty but also undeserving Visigoths -- and if it gets soaked enough to hurt epoxy they've got worse problems with the wood and the 80CrV2, anyhow.
That said, I think switching to G/Flex is good insurance. Sorta like the (very old) saying in the 'puter industry: nobody ever got fired for buying Microsoft.
Thanks again, all. BF is a wonderful community.
Andrew
*(here's a link; I have the full paper w/ pix and detail if anyone's interested)
**(from that past life I happen to have a patent in hydrocarbon chemistry so that's something I get well.)
