You can also remove broken taps and or steel screws and bolts from aluminum using nitric acid. It will dissolve the steel and leave the alum bright and shiny. Just use a glass tube over the hole to pour the acid down.
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On January 20, 2019 at 6:22 PM n4buq <email@example.com mailto:firstname.lastname@example.org > wrote:
I did not know alum would etch steel that way. Perhaps useful for more than just taps.
As for the larger taps etching faster, I'd guess it's due to the larger surface area.
Barry - N4BUQ
----- Original Message -----
> > From: "Ovidiu Popa [Business]" <email@example.com mailto:firstname.lastname@example.org >
To: TekScopes@groups.io mailto:TekScopes@groups.io
Sent: Sunday, January 20, 2019 4:20:22 PM
Subject: Re: [TekScopes] UNC Taps
In such cases I just etch away the broken tap in a supra-saturated hot
solution of alum. May have to "cook" the aluminum part overnight, but the
result is perfect. For large aluminum parts, I just use a double turkey
aluminum pan, dip the part in the alum solution (broken tap side down),
place it on the barbecue, when it's close to boiling add more alum until
saturating the solution, and leave it overnight (make sure the temperature
is high, but below the boiling point).
I've etched taps from 2-56 to 3/8-24. Interesting enough, small taps take
longer time to etch away.
Won't work for broken taps in steel, of course.
>Then one day I had a hardened set screw
>sieze and break in a nonreplaceable machined aluminum component (a
>heat block put together without anti-sieze). If it was a regular screw
>I could have drilled it out but trying to get that one out is like
>trying to drill through a rock in a lump of butter. After many bad
>words I pulled the disintegrator out and got it set up. It's a bit of
>a pain and it gets messy, but it took about 10 minutes to remove the
>screw and clean up the hole.