Loctite - Can I warm it up, move the joint and let it cool again?

I've made a crankshaft from a composite of 3mm steel rod and brass for a Stirling engine. The plans said to solder the pieces together, but I've used Loctite 403 instead. Works perfectly fine.

However, the alignment of the parts isn't quite correct and I need to adjust it a bit. If I gently warm the loctite until it moves, will it 'loctite' again when it cools?

Steve

Interesting question Steve but I have always assumed that once heated to break the bond that was it and you would need to clean up and start again.

Norman

Loctite sets chemically not by cooling. This implies it is not a thermo setting plastic so once the bond is broken it cannot be remade.

Martin

I think 403 is thread lock so should move without heat, just a bit of pressure. I think heat destroys the bond, not melts it so clean off and make a fresh joint. Will the Stirling crankshaft get hot enough to destroy the bond when in normal use in which case silver solder might be a better bet.

Hi David, 403 is an instant adhesive, see **LINK**.

Steve, it will bond together when it cools as far as you may be able to move it with your hands, but its structural strength will be compromised and will probably fail under a real load. As has been said, you will have to dismantle it, clean all to old adhesive off and use fresh.

Regards Nick.

Steve,

With due respect to earlier respondents: you may possibly get away with it.

The classic anaerobic Loctite grades cure into something resembling Perspex [which is thermoplastic] and, although too much heat will burn it, just the right ammount will soften it.

Success or falure will depend upon a multitude of factors

• Size and fit of Parts
• Grade of Loctite
• Control of temperature
• Distance to be shifted
• < etc. >|

but it is fairly common practice amongst amateur Clockmakers; having been 'promoted' by John Wilding.

If the impact of failure is not too high ... I would give it a go.

MichaelG.

To get the Loctite join to break down do that you can move things it has to be heated so much ( Circa 270 C) that the function of the Loctite is no longer valid. Heed the advice and dismantle and clean thoroughly and re-do the joints.

Clive

Interesting responses! There is very little load on the constituent parts compared to what 403 will normally deal with and I just need to tweak the alignment a fraction (it looks like the holes that take the journal pin are slightly out). The fit is sound, so it looks like a case of go gently and see what happens.

I shall be back shortly...

Steve

Steve,

My apologies ... I missed the fact that you were using 403

This is NOT a 'classic anaerobic' so please ignore my advice.

MichaelG.

Tweaking didn't work, the crank assembly just binds somewhere else now and tweaking again caused the loctite to fail, so I'm going to remake the crankshaft assembly and do a proper job, some of the (factory drilled!!) holes must be out of alignment in the original assembly.

Steve

Edited By Steve Withnell on 31/12/2015 14:35:35

My smallest hot air engine has a 3 mm crankshaft with ball bearing big ends on it, so it's glued together with a high strength retainer(not Loctite), it has not fallen apart yet. Sorry you can't quite see the crankshaft, only the big ends.

Ian S C

Hello Steve

Loctite are Anerobic Resins . This means that they cure in the Absence of Oxygen or Air. The curing process is that they change from a liquid to a solid/ plastic in the absence of air. When they are in the bottle , the Air in the bottle keeps them as a liquid. When you use Loctite to join say a wheel on to an axle , the absence of air in the small/ tiny gap between the wheel and the axle causes the Loctite to cure and it becomes a plastic. Loctite products are prone to failure due to Shock . So this means you must use a Keyway/ Key to transmit the force. Basically the different Loctite products have different strengths.

About twenty years ago I made the same mistake as your correspondent in that I Loctited a reversing lever on to a shaft in the wrong place. I tried to heat it up with no success so had to drill out the shaft and make a new shaft.

regards

Brian Lee B.SC, M.Sc.

I used blue Locktite to hold a flywheel on a chain saw. Took it in for a tune up and they did not tighten it up sufficiently and it wallowed out the bore. It was still retained by a bolt on the end, and the keyway was still there it just wobbled. Made it run true and let it set up. Only lasted 20 some years till the rest of the saw wore out.

.

Brian,

If only that was still true !!

In comparatively recent years, "Loctite" has become a Henkel brand-name for a wide range of materials ... only SOME of which are anaerobics resins. ... Steve's "403" being one that is not.

[ please see my earlier posts ]

MichaelG.

Steve,

Make a simple test with scrap materials with the same clearances etc as your crankshaft and try it. If it works please let us all know.