Sunday, July 24, 2016

Removing Broken Stem Bolt with Chemistry / Alum


The components of the experiment: stem with broken bolt, alum powder

I think I did one or two posts back when I broke off one of the face plate bolts on this stem while using a torque wrench, and then tried to get the broken part out with drills and extractors and whatnot, but I can't find those posts. Partly I blame the custom blog search widget, which seemed quite useful and effective back in the day, but that now seems close to useless at finding old posts. So this particular new post has a particularly literal title in hopes that I may be able to find it someday, again, if the need arises.

The one kind-of-related old post I did find was "Improper Installation May Yield The Fastener", which certainly captures the sense of what I was feeling I had when I broke off a bolt using a torque wrench. Anyway, no matter what I tried, that broken bolt refused to come out. So rather than totally destroy the stem trying to remove it, I chucked it into the "may fix someday" box, and went on with life.

Lo, behold, I recently came across this video by Youtube mechanical wizard AvE about using an alum solution to remove broken studs from aluminum heads, which seemed to have potential for my broken bolt stuck in an aluminum stem situation. There's another one where he compares alum vs nitric acid for doing the job (alum wins). AvE is a kind of genius mechanical hacker from Canada, and I thank him for this information, in addition to his awesome "BOLTR" (Bored Of Lame Tool Reviews) teardown videos. His language is salty, but his engineering and machining is inspiring.

Before picture, broken off face bolt on the right

My plan is to mix up a concentrated solution of alum with heated water, then let the stem with the broken bolt chooch in there for a few days to see what happens. "Chooch" is a word that AvE uses often, and I like it. It's so hot in Phoenix right now that if I just leave the stem and solution outside, the heat out there should help the reaction along. Will it chooch? Watch this space for future updates. I'm hopeful. It would almost undo the lasting shame of twisting off a bolt with a torque wrench. Almost.

 

2 comments:

  1. This is at least as good as when I tested Simple Green to see if it really WOULD dissolve aluminum. I look forward to your future updates!

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    Replies
    1. Well Steve, after a couple day stewing in the alum broth, she still ain't chooching. I'll leaver her in there a few more days to see what happens, but I suspect this stem bolt is some type of super-skookum stainless alloy of unobtainium and meteorite extract that's resistant to alum. We'll see.

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