I'm finally getting back around to fixing up my little die filer. Its
chuck is pretty munged after years of having files jammed into it, and
it doesn't work right anymore (i.e. doesn't hold the file parallel with
the shaft). I figure I'll mill away the "fixed jaw" and make a hardened
shim and glue it on. There will be little stress on the glue joint as
it will be held in compression, but there will be some. I'll be gluing
a ground surface to a milled one. Would cyanoacrylate (superglue) be
the right stuff to use?
If you want compression strength, a good grade of epoxy (not hardware-store
stuff) will give you around 4,000 psi or, if it's 100% solids, a little
more. Cyanoacrylate is a fraction of that, and its adhesion isn't nearly as
good as properly applied epoxy. One-part polyurethane (Gorilla Glue) is
somewhere in between.
I don't think you need a lot of compression strength for that job.
Personally, I'd soft-solder it and screw the paint (around 5,000 - 7,000 psi
compression, and good adhesion). But my second choice would be an
aluminum-filled epoxy. I think that's what JB Weld is, but I've never used
the stuff. The tensile strength of al-filled epoxy is questionable but its
adhesion strength is good, if you know how to apply adhesive to metals (a
long story, for another day). But its compression strength may be somewhat
higher than unfilled epoxy. Anyway, industrial-grade aluminum-filled epoxies
can run up to 6,000 psi or so compression.
My choice for ease and (probably) perfectly acceptable performance would be
polyurethane. It covers a lot of sins, partly because it's flexible and
partly because it has excellent adhesive strength.
Another good choice, but only a LITTLE DAB in the center if you don't
want it to foam out. Make sure it's clamped!
The important part is thorough degreasing with acetone, lacquer thinner
or even nail polish remover.
I worked on a project once which used a mind-boggling epoxy from
Armstrong to hold things together where we could not use bolts
(electrical conductivity would have been bad). It was a two part epoxy
which could be made more or less flexible by varying the ratio of parts
A and B, and required a long time (days) to cure at room temperature, or
a much shorter time at elevated temperatures. A12 sounds like it might
be the stuff:
Maybe. Industrial epoxies are a complicated story. Most RTC
(room-temperature-cure) systems use a polyamine hardener, and A12 sounds
like it might be one of those. They often benefit from a cure at slightly
elevated temperatures, but they're usually cured at *one* temperature for a
given amount of time. Polyamine hardeners are versatile and can give good
performance. They're a common type of hardener in hardware-store epoxies,
and, typically, they're mixed at a 1:1 ratio with the epoxy itself, at least
in consumer versions.
When you hear someone say "A/B," however -- especially when they're talking
about high-performance, industrial-grade epoxies, they're often talking
about "A/B cures," rather than about mixing parts "A" and "B." An A/B cure
is a two-stage cure, used with different hardeners, and it produces higher
strength, toughness, and heat tolerance than typical RTC epoxy systems. A/B
cure epoxies are used for laminating commercial and military aircraft parts,
Formula 1 race-car parts, and so on. They're also used for bonding metals in
A typical A/B cure would be, say, 6 hours at 200 deg. F and 10 hours at 250
deg. F. That's not representative, just one possible example.
Don't try it with Elmer's Two-Part Epoxy Adhesive. <g>
CA is very brittle so it likely won't last a long time unless you just
don't change your files. Epoxy is much better, more flexible. JB Weld
would probably last forever, at least if you degrease the joint first.
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