Glueing query

I need to glue a stack of 40+ brass and steel pieces. They will be pulled together with three tie bars. They are a bit finicky to get
lined up so I need a reasonably long wet time. I also need a "thin" adhesive as I do not want a tolerance build up. At the moment I am considering an anerobic like Loctite 290 (which I have plenty of) but even that goes off relatively quickly once the stack comes together. The adhesive is just "braces" hopefully the tie bars will be the "belt".
Any ideas?
Richard
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Richard Edwards wrote:

glue up small batches and then once they have gone off glue the 'clumps' together?
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Araldite, preferably the 24 hour setting type. Spread very thinly and squeeze together hard. Alternatively, if you feel Araldite would be too thick, what about varnish?
David
--
David Littlewood

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writes

There are many epoxies that are thinner than Araldite. Try your nearest model/hobby shop.
Henry
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Dragon wrote:

Yes.
The usual Araldite you buy in shops is rubbish, mostly because it's old and has been lying around in the shop for years, but also because the domestic variety just plain isn't very good (though Araldite do make some good industrial glues).
A solution may be to thin an available epoxy, preferably not shop Araldite, with isopropanol (aka IPA, Iso-Propyl Alcohol, propan-2-ol, etc).
This tends to slow down the setting time of epoxies quite a lot, especially if more than about 4% isopropanol is used as thinner. Test first though.
For the DHP (the manufacturer) epoxy I normally use for gluing, 10% or more IPA will slow the 30-minute version down to about 12-24 hours, depending on temperature.
If polyester glue is suitable, thinning it with styrene will probably give a better result than a thinned epoxy in constrained conditions, as the styrene thinner will chemically combine with the glue, whereas IPA in epoxy will have to evaporate eventually somehow.
It depends on how big and thick the pieces are though, and the required gap.
-- Peter Fairbrother
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I have some Araldite (24hr) that must be over 10 years old, and it still works fine. Maybe takes a little longer to go fully hard. Most of the Araldite I have binned (about two lots over 30 years) is because I couldn't get the caps off.

This is a most useful tip, thanks.

Not that easy to get hold of styrene (and as I recall, it stinks).
David
--
David Littlewood

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David Littlewood wrote:

I can only suggest you try a good fresh epoxy and see the difference. As I said, I mostly use NHP 30 minute which is about a tenner for 8 ounces, but there are other similar types.
It's like chalk and cheese, really it is, and you will most likely start using epoxy for things you previously thought epoxy couldn't do.
It depends on the precise formulation, and it's different for epoxies where the catalyst is in a much smaller bottle, but in general a good epoxy will begin to lose a noticeable amount of adhesion after about 6 months, and will start taking noticeably longer to harden after about a year.
There is a trade-off the manufacturers make about life and properties - some of the very best high-tech epoxies have a shelf life of only a month, and three months is common.
For the epoxies I mentioned, the shelf life is in between - a very short shelf life is too restricting. NHP and West Systems epoxies will still be okay after couple of years (West catalyst goes off after about a year, but the resin itself lasts longer) - though both are still best when fresh.
It's not essential, but if you keep epoxy in the bottom of a fridge it will last longer. Don't freeze it though, and warm to room temperature before use.

It's straightforward to get hold of styrene. Most of the people who supply boatbuilding (as opposed to boat repair) polyester resins also supply it, and you can simply buy it on ebay. Eg:
http://www.cfsnet.co.uk/cgi-local/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2ecfsnet%2eco%2euk%2facatalog%2fCFS_Catalogue__POLYESTER_RESINS_1%2ehtml&WD=styrene&PN S_Catalogue__Styrene_279%2ehtml%23aCSTSTY_2d001#aCSTSTY_2d001 http://thefibreglassshop.co.uk/shop/article_35/Styrene---1L..html?shop_param=cid%3D135%26aid%3D35%26 http://cgi.ebay.co.uk/1-Litre-Styrene-Additive-Thinning-Resin-GRP-Work_W0QQitemZ220499732908QQcmdZViewItemQQptZUK_Crafts_Other_Crafts_EH?hash=item3356cee9ac
It's slightly nasty stuff, be careful when using it - most important is to avoid breathing it.
And yes, it stinks.
-- Peter Fairbrother
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wrote:

I think it depends on the application but you could try good old shelac and paint each one inturn then clam up and gently heat, the shelac will melt and fuse giving a thin joint. If you go for araldite 24 hour, raise the tempreature and it will thin and set quickly as well as giving a thin joint, but not as thin as shelac. Peter
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On Tue, 16 Feb 2010 17:18:37 +0000, Richard Edwards

Gentlemen,
Very many thanks for your prompt and interesting suggestions.
I am looking for a maximum glue thickness of .03mm or thereabouts so "thin" is of the essence.
Based on the suggestions I think I will pursue the IPA thinned epoxy option and the Shellac option. I feel that I should have some shellac flakes on the shelf anyway. I see some experimenting coming on <G>
Peter, you mention DHP, I have searched and searched but probably cannot see the wood for the trees <G> Can you give me a better pointer to the product or manufacturer?
Richard
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Richard Edwards wrote:

My bad - should be NHP. Sorry about that.
Should be readily available, and much favoured by rocketeers. 14,400 worldwide and 538 UK-only google links today.
I'm not recommending them - well actually I am a bit - just saying that that's what I use for gluing and similar jobs.
For composite layup I use West Systems epoxies. Composite layup epoxies are usually thinner than gluing epoxies, which may be of interest to you, though a small-but-useful pack of NHP at around a tenner is about 1/3 the price of a small-but-useful pack of West Systems at about 30.
NHP adheres better than West for gluing purposes.
If you possibly can, buy fresh epoxies from someone with a large turnover. After a few months in stock they begin to stop working as well as fresh ones, the difference is quite noticeable.
There are better-performing epoxies than these available, but all the ones I have tried were ouch! expensive.
YMMV, but probably not by that much.
For another perhaps unexpected but possibly quite apt suggestion see: http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item20186922795&ssPageName=STRK:MEWAX:IT
for 1 mil (?=0.025 mm?) FEP film. Just be be careful not to overheat it too much, if it gets really hot it can give of dangerous fumes above about 300 C. Melts at 260 C, in theory.
But you can safely put it in eg a hot domestic electric oven. I'd recommend at say 230-250 C when compressed, if your oven goes that high and if SWMBO will let you...
Again, do a trial run first if at all possible. Using sheet glue is a different technique, and things have to be very clean,
-- Peter
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