Monday, February 25, 2008

Epoxy As A Repair Agent For Aluminum

Epoxy As A Repair Agent For Aluminum

I mentioned several days ago
a stupid accident that snapped a couple of pieces of aluminum out of the CI-700 mount. I have not found any solution that I am completely happy with for fixing this. Welding the two broken parts back in place would require complete disassembly of the mount.

There is a soldering product called Alumaloy--which appears to be largely zinc. You heat the aluminum parts up with a blowtorch, and that's hot enough to melt the zinc. Zinc is not as strong (or as flexible) as aluminum, but it isn't orders of magnitude worse than aluminum. A number of comments that I found indicate that Alumaloy works, but it isn't as easy as the demonstrations of it suggest. And I would still have to the take the mount entirely apart to do this.

However, epoxy might make sense. Epoxy seems to have a yield strength in the 12,000-15,000 psi range, while aluminum is in the 15,000-20,000 psi strength range. This isn't going to be anywhere as strong, but it's worth a try. I've got some five minute epoxy that I used to repair the counterweight lock knob which broke, and while I will never want to treat it roughly, it doesn't seem to be preparing to fall apart. Once I have everything in position, I'll use the blow dryer to accelerate the curing process. It's a confined space, so this should work well.

UPDATE: For some reason, the 5 minute epoxy would not set--and being as the broken parts were upside down, getting them to stay in position was hopeless. I'm told that J.B. Weld epoxy, which is made specifically for metals, works better.

Fortunately I was able to disassemble the mount head, and ended up with a single small part with nothing electrical on it that I could feel comfortable taking to a welding shop.


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