Re: ATM Adhesives

[Dennis Rech <dennisrech@home.com>]

>Jerry Dove writes,
>>      I jumped in and was swearing that Polyurethane glue was the best stuff I
>had ever used for gluing surfaces
>>together, especially for filling gaps.
>>
>>      Well, I've had some more experiences with this stuff since then and
>thought I'd pass on the information, maybe
>>save someone some grief.
>>
>>      This stuf does seem to glue very well, but I've found that it is also very
>brittle. I've used this stuff many
>>times and never had any trouble until the other day when I just happened to
>drop the pieces.  They separated as it they
>>had not been glued at all.  Apparently any sharp rap fractures the joint
>very easily.  So for a scope framework, this
>>could be disastrous if it were dropped or something.  
>
>I too have been using this glue, but have found from past experience that 
>it's best to complement the glue joints with deck screws, so fracture has
>not been a problem. The gap filling feature of polyurethane glue has been
>an excellent feature.
>
>Andy
>Andy Saulietis / ISS Alt-Az-Fp Drive Systems
Very interesting.
I just went out to the shop and gathered up some of my test samples and
glued up cut-offs and gave them a small "rap" test. With a 12 pound sledge.
In every case the wood broke instead of the glue joint. I also had some
steel hinges glued to 3/4 inch ply. I gave them a daity 12 lb sledge rap
and them several not so dainty follow up raps. The hinges are horribly
mangled but are still hanging on to scraps of wood. 
Are you glueing formica or something very smooth? 
I have gone through ten or so bottles of this stuff in the last two years
and have never had a failure as long as the surfaces were slightly rough
and failrly clean and dry. 
I usually leave nails or screws in the joints. The glue joints usually
still have a small amount of resilency after a couple of months. I have
never seen a brittle joint.
Could there be some reaction to humidity or lack thereof?
Keep us informed.

Dennis Rech
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