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

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

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

Not necessarily. See 3M Scotch-Weld.


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

In very general terms, yes.


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.

Of the consumer-grade polyamine-cure epoxies (most of the stuff you're
likely to encounter), expect a 48-hour time at room temperature
for full cure, and about a week to get really hard.


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.

You need at least 0.005" for a high-strength bond, metal-to-metal. A little
more is better.


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.

That's how many aircraft wing skins are assembled. The epoxy provides sheer
strength, and rivets resist peel failure. It's called rivet-bonding.


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.

Ordinary amine-cure epoxies lose strength in the mid-200s F. Some of the
industrial products are good up to 350 F or more.


Iny thoughts?

Using epoxy for assembling metal parts is not a trivial thing, if you want
decent performance. It's time to get on the phone with Devcon, or 3M, etc.,
engineers.

--
Ed Huntress

On Aug 6, 3:48*pm, "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?
--
EA

The heat effects seem to vary a lot from one mfg. to another. All the
ones I examined give the maximum heat they will stand up to. I was
looking for an epoxy to use in assembling fiberglass pallets to carry
circuit boards through the solder reflow oven. The pallets are made
from circuit board strips salvaged from panels of curcuit boards. I
needed an epoxy to withstand 250-260 degree C. The only one available
at reasonable prices is JB weld.

It does turn dark over time - many months. A few times it has
eventually lost it's ability to hold onto the fiberglass board
material. The pallets have been through the oven perhaps a thousand
timed and still are ok. I recently had to rebuild some pallets because
the circuit board epoxy was delaminating the layers of FR4 material.
But the JB Weld was still holding and had to be cut away and sanded
down to the bare board material.

JB Weld takes up to 12 hours to cure. I speed it up with a heat gun.
Then about 1/2 hour.

Hope that helps some.

Paul

"Existential Angst" wrote in message
...
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.

"ATP" wrote in message
...

"Existential Angst" wrote in message
...
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.

"ATP" wrote in message
...

"Existential Angst" wrote in message
...
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.

I was thinking that. I think of the common Loctite formulations green is
sleeve and bushing locker. That's what I used on the transmissions input
shaft bushing where it goes into the primary case on my wife's old Fatboy
anyway. Never looked at the heat rating. That shaft is constantly splashed
with primary oil so it doesn't get to hot, but its also what I used for a
press in sleeve for the cooling system on a truck engine. Never had a
problem with either one.

We found that the 5 Minute 2 part, and under the 5 too, are not well
suited to water even after full set. The boats sank. The more
conventional times were fine.

Brian Lawson,
Bothwell, Ontario

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...

"Existential Angst" wrote in message
...
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?

I did some side-by-side trials of epoxies and for steel-to-steel I like JB
Weld best of the commonly available ones.

I have changed some of my joints so that there is mechanical advantage
making the epoxy joints stronger (e.g. recessing a cylinder into a flat
plane even slightly makes the joint much stronger than just gluing the flat
of the cylinder to the said plane). I think it is worth looking at what
forces will be present and how to minimize them in any particular design.

I made a few stone statues for the garden. The epoxy joints were strong
indoors but all fell apart in the hot sun outside. Not all of them were
exposed to UV light so I assume heat was the primary factor.

--
Michael Koblic,
Campbell River, BC

In addition to Ed's excellent response, I would like to add that the old technique of casting mounts and bearings in place is
alive and well. This was done for years using lead alloys. The lead alloys have been taken over by epoxies. However, as bearings
require service, it is usually the bearing boss that gets epoxied. An excellent example of this usage is the positioning of engine
supports in large ships. These engines are very often built into the ships during construction. The engine mounts are optically
aligned with laser and cast in place with a product called "Chalk Orange". The advantage of using this epoxy is that when it
cures, there is no shrinkage. I actually used this myself when I positioned my oil bearinged propeller shaft/tube in my sailboat
several years ago, as welding would have disturbed the shaft bearing alignment.
Steve

"Ed Huntress" wrote in message ...

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

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

Not necessarily. See 3M Scotch-Weld.


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

In very general terms, yes.


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.

Of the consumer-grade polyamine-cure epoxies (most of the stuff you're likely to encounter), expect a 48-hour time at room
temperature
for full cure, and about a week to get really hard.


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.

You need at least 0.005" for a high-strength bond, metal-to-metal. A little more is better.


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.

That's how many aircraft wing skins are assembled. The epoxy provides sheer strength, and rivets resist peel failure. It's
called rivet-bonding.


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.

Ordinary amine-cure epoxies lose strength in the mid-200s F. Some of the industrial products are good up to 350 F or more.


Iny thoughts?

Using epoxy for assembling metal parts is not a trivial thing, if you want decent performance. It's time to get on the phone
with Devcon, or 3M, etc., engineers.

--
Ed Huntress

On Aug 6, 11:02*pm, "Steve Lusardi" wrote:
In addition to Ed's excellent response, I would like to add that the old technique of casting mounts and bearings in place is
alive and well. This was done for years using lead alloys. The lead alloys have been taken over by epoxies. However, as bearings
require service, it is usually the bearing boss that gets epoxied. An excellent example of this usage is the positioning of engine
supports in large ships. These engines are very often built into the ships during construction. The engine mounts are optically
aligned with laser and cast in place with a product called "Chalk Orange".. The advantage of using this epoxy is that when it
cures, there is no shrinkage. I actually used this myself when I positioned my oil bearinged propeller shaft/tube in my sailboat
several years ago, as welding would have disturbed the shaft bearing alignment.
Steve

"Ed Huntress" wrote in ...

"Existential Angst" wrote in ...
Awl --

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

Not necessarily. See 3M Scotch-Weld.

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

In very general terms, yes.

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.

Of the consumer-grade polyamine-cure epoxies (most of the stuff you're likely to encounter), expect a 48-hour time at room
temperature
for full cure, and about a week to get really hard.

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.

You need at least 0.005" for a high-strength bond, metal-to-metal. A little more is better.

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.

That's how many aircraft wing skins are assembled. The epoxy provides sheer strength, and rivets resist peel failure. It's
called rivet-bonding.

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.

Ordinary amine-cure epoxies lose strength in the mid-200s F. Some of the industrial products are good up to 350 F or more.

Iny thoughts?

Using epoxy for assembling metal parts is not a trivial thing, if you want decent performance. It's time to get on the phone
with Devcon, or 3M, etc., engineers.

--
Ed Huntress

Learned something new.
Thanks
Karl

On Aug 6, 11:02*pm, "Ed Huntress" wrote:
"Existential Angst" wrote in message

...

Awl --

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

Not necessarily. See 3M Scotch-Weld.



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

In very general terms, yes.



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.

Of the consumer-grade polyamine-cure epoxies (most of the stuff you're
likely to encounter), expect a 48-hour time at room temperature
for full cure, and about a week to get really hard.

This is good advice, as is the contrapositive: In really cold weather
these epoxies can go for weeks without ever getting hard. Don't expect
a repair made in an unheated garage in upstate New York in December,
to be ready in March :-).

Tim.

As a further contribution to this thread, there are many applications coming on line in the shipbuilding,automotive and aircraft
industry in the metal to metal bonding area. These epoxies are not available to the general public. An example is the chassis of
the Lotus Elise. It is fully bonded aluminum without welds. In the ship building industry, the major detractor to adhesive use is
not structural. It is insurance and IMO regulation issues relating to heat vulnerabilities during fires.
Steve

"Existential Angst" wrote in message ...
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

"Steve Lusardi" wrote in message
...
As a further contribution to this thread, there are many applications
coming on line in the shipbuilding,automotive and aircraft industry in the
metal to metal bonding area. These epoxies are not available to the
general public. An example is the chassis of the Lotus Elise. It is fully
bonded aluminum without welds. In the ship building industry, the major
detractor to adhesive use is not structural. It is insurance and IMO
regulation issues relating to heat vulnerabilities during fires.

Dental epoxies are impressive as well. They have one now that cures under
UV. It's very hard upon curing, enough to stand up to some pretty brutal
teeth cleaning/gum surgery.

--
EA


Steve

"Existential Angst" wrote in message
...
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

On 8/7/2010 5:02 AM, Steve Lusardi wrote:
The
engine mounts are optically aligned with laser and cast in place with a
product called "Chalk Orange".

"Chockfast Orange"?

http://www.chockfast.com/itwproducts.html

Kevin Gallimore

axolotl wrote:
On 8/7/2010 5:02 AM, Steve Lusardi wrote:
The
engine mounts are optically aligned with laser and cast in place with a
product called "Chalk Orange".

"Chockfast Orange"?

http://www.chockfast.com/itwproducts.html

Kevin Gallimore



Handy stuff.
Thank you.

--

Richard Lamb