POTD- PROJECT OF THE DAY: What Did You Make In Your Shop Today?

Inferno said:
They are Alum crystals.
I was trying to use a hot Alum bath to remove a broken high speed drill bit. It was heated for over 36 hours. I guess the crystals form when it cools?
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More background is needed about just exactly what you were removing the broken HSS drill bit from??? :)
 
dkemppai said:
More background is needed about just exactly what you were removing the broken HSS drill bit from??? :)
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More importantly, did this work? I have a broken tap I need to remove, it just won't come out. HSS 6-32 tap in aluminum.
 
dkemppai said:
More background is needed about just exactly what you were removing the broken HSS drill bit from??? :)
Click to expand...
I had it in the other tread where I showed the small injury I sustained but I can repeat it.
I was drilling a 1/8" hole in 1" thick aluminum. The drill bit started to bind so I was clearing it out regularly and going slow. As it started to cut through the back it bound up and exploded. A shard hit my lip and ricocheted to my arm. Luckily my lip wasn't cut but my arm was.
Only a tiny shard of the bit was sticking out of the aluminum. I tried to grab it but the bit was totally stuck.

WobblyHand said:
More importantly, did this work? I have a broken tap I need to remove, it just won't come out. HSS 6-32 tap in aluminum.
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Yes, it worked, sort of.
I bought the Alum in the spice area of my grocery store. It wasn't a lot.
The general directions for removing/dissolving the broken bit says to have a super saturated solution. With the amount of Alum I had, it wasn't supersaturated.
But it worked, kind of. I saw the action of the bubbles showing it was working but they weren't as fast as they should have been.
People say that it should only take a couple hours but I had my solution going for over 3 hours and only managed to dissolve about 1/4" of the bit.
I haven't given up. I bought 2 pounds of Alum and it will be delivered today. It was only $12 so not that expensive.

The secret is heat. When the solution cooled down, the dissolving action ended.

I used my regular SS cooking pan and a measuring cup as a double boiler. Both were damaged when doing this. The pan because the glass measuring cup danced on the bottom of the pan, scuffing it with a fine scuff. This will affect cooking in the future, I think.
The measuring cup ended up with what appears to be an aluminum oxide finish where the solution was. It mostly came off with scrubbing with a green pad but it's not all coming off. I'll attack it later.

The aluminum piece came out with a nice fine oxide-looking finish. I am going to test it someday to just give a fine finish on parts. Safer than using battery acid.

I have no doubt the bit will dissolve completely with a more saturated solution.
 
@Inferno
Thanks for that explanation of the Alum process.
I had not heard of it before you mentioned it.
I have a candidate broken tap waiting for me at home. :grin:
 
First-order rate reactions are always limited by temperature if all reactants are available in excess. Whether degreasing, performing electrolytic derusting, or eating away an iron-based tool with alum, temperature will make the difference between a slow reaction and an aggressive reaction. Same goes for injuries from chemicals. Always consider temperature when using the chemical cookbook. The solubility of alum doubles in the interval between 50C and 80C, for example. That's why you ended up with gemstones when the solution cooled! Also consider that alum eats chromium the same way it eats iron, so this process will work with 300 series stainless, but not 400 series.
 
pontiac428 said:
First-order rate reactions are always limited by temperature if all reactants are available in excess. Whether degreasing, performing electrolytic derusting, or eating away an iron-based tool with alum, temperature will make the difference between a slow reaction and an aggressive reaction. Same goes for injuries from chemicals. Always consider temperature when using the chemical cookbook. The solubility of alum doubles in the interval between 50C and 80C, for example. That's why you ended up with gemstones when the solution cooled! Also consider that alum eats chromium the same way it eats iron, so this process will work with 300 series stainless, but not 400 series.
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“Chemical Cookbook?” Muuhahahahaha!


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