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Old 07/23/2003, 10:40 AM   #69
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Join Date: Jun 2003
Posts: 4,228
Originally posted by Zephrant
I've not tried #42 yet, but have been considering it. I have heard that it is pretty thick, moose-snot comes to mind as the term used. I don't know if you could force it in the gap without using large pins, then you would have a lot of ooze when you pulled them.

Anyone try it before?

It is fairly thick and should not (IMO) be used with the "pins" method. One thing you really don't want to do is compress Weld-on 40/42, what you end up doing is squeezing it all out ending up with a dry/weak joint. Weldon 40/42 does not act in the same way as "normal" solvents as it is not a solvent at all but an acrylic resin that attacks the acrylic to be glued, albeit not nearly as much as regular solvent. Think of 40/42 as a "glue" whereas solvent creates a direct bond between two pieces.
If you use 40/42, you need to leave a slightly angled gap to fill - maybe .060-.090" Overfill this and allow for shrinkage, it will shrink about 20% +/-. Then flush cut, sand, and finish. many people leave a small piece of acrylic in the joint to create this gap - kinduva spacer of sorts, this piece is later cut off during finishing.
Another thing about 40/42 is you don't want to leave to too large a gap as it creates alot of heat in it's reaction - it can put off enough heat to smoke and *possibly* (I've heard stories) self combust. With 40 you can compensate for this somewhat by adjusting your mix ratios but cure time takes much longer, with 42 this is not allowed for at all as it is pre-portioned.
As Naga pointed out - it is expensive at $180 for the gun, $28 per cartridge, and about $1.50 per tip for the straight tips up to $14 per tip for the flexible ones which are disposed of after each use. If you are in the business and do this sort of thing often, it's a marvelous time saver (time is money) but probably doesn't make a whole lotta sense for most DIYers/hobbyists IMHO.


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