"ATP" wrote in message
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"Existential Angst" wrote in message
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Awl --

First, is "two-part epoxy" redundant? Does "epoxy" nec. imply two parts?

Next, does the strength of a two-part epoxy vary with its setting time?
Intuitively, I would think the longer the stronger.

The classic is "5-minute epoxy", but I believe I have seen 60 sec epoxy,
and I have 90 minute epoxy.
I find 15 minutes to allow for a few parts without rushing, and without
waiting forever to cure. Altho I have also found that the epoxy is not
really hard in that time.

The stuff I have now is Permatex (a 30 min epoxy), but DevCon and Loctite
are big players, with big-time industrial uses, such as epoxying
bearings, instead of press-fitting them into their housings. I believe
DevCon stated that epoxying bearings is in fact the preferred method,
being stronger than press fit.

The shear strengths are enormous, but require at least .010 on the radius
for good bonding. So a slip-fit for epoxy would be counterproductive.

In some of my proposed assembly methods, I could use set screws, pins,
epoxied pins, or just epoxy -- typically nominal 7/8 alum round in 16 ga
SS tubing, or some such.

I thought epoxying would be slam dunk, and indeed it saves machining, but
goddamm, you gotta pick yer poison, it seems. I could see arguments for
actually using a mechanical method AND epoxy, in some applications.

A feature of epoxy, which could be both good and bad, is its instability
to heat. I think boiling water, or at least not that much hotter, can
undo epoxied parts.

Iny thoughts?
--
EA
I'm not picturing exactly what you're doing, but Loctite makes some close
fit "annular space" compounds, I used one once to set a brass sleeve for a
diesel injector.

The Loctite line of retaining compounds for cylindrical parts are more
suited to bonding bearings than epoxy. They also withstand higher
temperatures. There are several types to choose from.

If you do use epoxy, you are correct that it needs a healthy gap. One way
to keep a cylindrical part centered in an oversize hole when bonding is to
use three small shims in the gap and let the cement fill the rest of the
gap.

BTW there are a lot of 1-part epoxies that cure with heat.