Anaerobic adhesive question

Can someone recommend the right anaerobic adhesive for me?

I need a strong adhesive for the permanent assembly of a project that consists of several parts that need to be aligned. The parts are steel shafts in close fitting cast iron bores. I am using 'Superfit 231' from Arc but find that this cures so fast that I am unable to correctly position all the components. Is there a grade that gives high strength but takes a few minutes to cure to facilitate positioning of components? Or is there a way of just slowing down the speed of cure?

I would think there is a grade of Loctite for that. Look at the Loctite website for details of their products.

Martin C

The spec says it should take 5 to 10 mins to cure, is it going off quicker than that?

I used Bondloc B638, it too has a <10mins cure time and it did take about 10mins. It was quite cold then, about 15C. You could try putting the Superfit and parts in the fridge for a while. That might slow it down.

Adrian

Loctite 603 has an open time of 8mins. Shear strength 3770 in steel.

Loctite 638 open time 4mins Shear strength 4500 in steel.

Loctite 641 open time 25 mins Shear strength 1700 in steel.

**LINK**

regards Martin

Loctite 609 (unless they've renumbered it...)

What assembly time do you need, to correctly position the components ?

How does this compare: **LINK**

https://tdsna.henkel.com/americas/na/adhesives/hnauttds.nsf/web/1716575D28E43176882571870000D860/$File/648-EN.pdf

MichaelG.

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Edit: if that’s too fast ... try this:

https://tdsna.henkel.com/americas/na/adhesives/hnauttds.nsf/web/062262D5231164B0882571870000D85C/$File/640-EN.pdf

Edited By Michael Gilligan on 24/04/2020 08:38:33

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For many applications, such as the one being discuss, I prefer to use slow cure epoxy adhesive rather than anaerobic adhesive. This gives plenty of open time and it forms a very strong bond with steel (and most other metals).

Mike

The Superfit 231 cures to the point where it is no longer possible to reposition the compenents within 60 seconds. I've had to undo the bonds with heat several times now but, even with practice, I am just not fast enough with assembly for this to be viable. I need 5 minutes at least.

Thanks for links to Loctite website. I note that the datasheets for both Loctitie 603 and 638 suggests that bond strength is 0% until 5 to 10 minutes so that should be fine.

You don't say what your "close fit" is but that is one of the main factors that will affect cure time, have a look at the second graph here and see how a 0.15mm gap gives 30mins before it starts to go off yet 0.05mm starts in 10mins or less.

Does anyone have any information about the minimum clearance for epoxy? I have had a look on the web but most of the references I can find are vague and rather general.

No actual use in mind today, just a more general query especially regarding the suitability of epoxy in place of HS retainers such as 648.

BR
Simon

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Thanks that is very interesting and may be part of my problem. My parts are close sliding fits. To get the 25mm shafts in the bores they have to to be exactly aligned and, once in, there is no discernable play. The shaft slides back and forth in the bore very smoothly though. The shafts measure 25.00mm and the bores (measured with my simple telescopic bore gauges and digital calipers so not high accuracy) are around 25.02mm. That would give a gap of only 0.01mm for the adhesive to fill. Is that why the adhesive is curing so promptly?

Don't forget that you may be able to undercut the shaft along part of it's length by a few thou (or whatever) to give you any gap that you need while maintaining its fit where it's needed.

Further to the undercut suggested by Bandersnatch I recall seeing this as official or at least semi-official advice from an industrial oriented source that would be expected to be reliable.

As I recall matters the suggestion was, when using loctite or similar, for a couple of thou undercut for less than the full width of the component to be retained. The idea being that the adhesive would be retained in the undercut reducing mess whilst the narrow flanges of the component extending onto the full diameter of the shaft at both ends would keep things in line as the adhesive reached full cure strength.

I suspect the source was a comparative assessment of the different ways in which a component could be quickly retained on a simple shaft without keys, splines et al without risking misalignment by tilting. I'm pretty sure it also covered things like tolerance rings and conventional adhesives like epoxies.

Worth remembering that the cure process of aerobic adhesives is somewhat catalysed by the metal surfaces of the components. Which obviously works disproportionately faster with very thin layers.

Clive

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Yes, it’s one of several factors ... but also note that several of the Loctite products are specified as being suitable for use [at appropriate assembly speeds] with slip, press, or shrink, fits. ... including the slow curing 640 that I linked earlier.

A couple of hours spent comparing some of the Loctite Technical Data Sheets would be time well-spent, I think.

MichaelG.

I've always undercut the shaft when using epoxy. Without that, I don't think you could get sufficient bond-line at all, for any sensible shaft fit.