I got the Permatex version of Loctite 660 yesterday (Permatex 20297). Before
I used it in anger I thought I would run a trial.

First of all I opened the 6 ml tube and found it empty! There was about 0.25
ml of the compound in it, enough to use it in the trial - just.

I drilled and reamed three identical blind holes in scrap mild steel: 0.25"
diameter, 0.382" deep. The ideal surface area of contact is 0.35 in2.
I cut three identical pieces of 0.25" uncoated mild steel rod (the actual
diameter 0.247"). I bent them at right angles at the same spot to give me
"twisting handles" for later. I cleaned the rods and the holes with acetone.
I applied the 20297 generously to one of the rods and to the walls of the
hole as far as possible and inserted the rod fully. I did the same with the
second rod using Loctite 262 threadlocker and JB Weld in the third hole.

After 22 hours, these were the results:

1) The 20297 could be easily popped and twisted by hand.
2) Neither of the remaining rods could be twisted by hand.
3) Using a 26" iron pipe with a 0.25" opening in one end as a lever I was
able to move both remaining rods.
4) The JB Weld popped suddenly. After this pop the rod could be moved by
hand.
5) The 262 rod could be moved with some effort. However, there was no
"popping" (catastrophic failure) and even after the rod was rotated for some
distance using the pipe it still could not be moved by hand.

Comments:

1) I do not know what conclusions can be reached from this test about the
20297. Who knows what was in that tube and how it deteriorated over time.
2) In some applications the mode of failure of the 262 may actually be
preferable to the JB Weld which is commonly used in the automotive community
as a retaining compound.
3) Given the small area of contact the strength of the 262 seems quite good.
My totally unscientific impression is that it required somewhat more
strength to rotate the rod held by it than to cause the failure of the JB
Weld. This is consistent with the figures each company publishes for their
respective products.

Conclusion:

There is no desperate hurry to replace the 262 in my applications for the
time being.

--
Michael Koblic,
Campbell River, BC