Existential Angst wrote:
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?

As someone mentioned, there are single-part epoxies, like scotchweld
2214 which cures at 350f, I think. Very hard when cured, very temp
resistant. also expensive and hard to get in small qtys.

Loctite etc. cure in the absence of air, which is why they don't
set until hidden away in a gap. anaerobic, is it? words fail me
at the moment.

I've been looking for a sub for above 2214 to bond piezo wafers to my
ultrasonic cleaning tank. Some idiot ran it dry and two of the wafers
shattered.

Amazingly, the hardest stuff I've found so far is used for attaching
golf club heads. Not sure if it will hack the temperatures. Only
one way to find out, I guess. Sigh...