Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.
whateg0 wrote: ↑Mon Jan 06, 2020 5:53 pm
Aside from some special high temp variants, most seem to have a working temperature of up to about 180F. I still don't see much about failure mode above that, but it doesn't really matter much, I suppose. I see specs for shear strength, but don't see much on tensile strength and temperature's effect on it. Again, doesn't matter much now. Based on what I ran into and the shear strength numbers, I can see I had PLENTY of adhesion for the job at hand. OTOH, better to have too much than too little and have the part go flying.
Dave
"Working temperature" just means that they don't guarantee full strength above that, though. If it still has half of full strength at 350F it isn't coming off.
I wonder if someone makes or could be convinced to make a special fixturing version with a specified release temperature?
armscor 1 wrote: ↑Mon Jan 06, 2020 4:59 pm
A workmate was using eyedrops to battle an eye infection, went to the refrigerator in the middle of the night and inadvertently put drops of Loctite super glue in his eyes, spent a week in hospital!
Have no idea what they used to dissolve the glue?
A hard lesson learned that work materials should never be kept in refrigerators that hold food and medicines.
Hope he fared well with that experience.
John Hasler wrote: ↑Mon Jan 06, 2020 6:16 pm
I wonder if someone makes or could be convinced to make a special fixturing version with a specified release temperature?
This is a great idea I'd never heard of before; another useful morsel of info from Home machinist.
I wonder if heat melt glue would be strong enough? Its low melt temperature would make it easy to remove, especially for delicate parts / materials.
Two things I can think of being a problem with hot melt glue are the fact that it doesn't adhere well to some surfaces, and maybe more importantly, it flexes.
I soaked the part in acetone yesterday evening when we went out to eat. Now I just need to finish assembling the item. I'm going to put the part in the oven a 400F and then drop it onto a room temperature pin for a (hopefully) nice tight fit. My math says it should go from 0.0015" of interference to about 0.002" of clearance on a 0.9" hole.
With hot melt glue you will need to have a thick layer under the part. This layer won't uniform so the part won't lay flat. As Dave noted, it also isn't rigid and isn't very strong.
Cyanolacrylate forms a very thin, uniform layer between surfaces.
It gets thin and sticks better when the parts are heated above the glue melt temperature; which isn't very high. I used it on a ceramic sculpture and it worked well that way. When everything was hot I could squeeze the parts together and find the exact position.
Of course, that material is porous and it didn't have to be strong.
