Broken Tap Removal

[Mosey]

I have a broken off a 2-56 tap in an aluminum head that I want to try removing with alum. If I immerse only the part of the head where the tap is in the alum solution, and keep the rest of the head (with the valve cages) above the surface, will this allow me to get only the tap to dissolve?

 

[rake60]

It should work, but if any other steel parts come in contact with the alum they will
be dissolved as well.

Rick

 

[Mosey]

Well, that would be the valve cages, which I am unhappy with anyway. I am thinking about remaking the cages from cast iron to replace the drill rod ones I now have in place. (I just don't love what I made previously)

 

[sub-xtx]

Hello,
you can try with EDM

 

[Mosey]

Sure, but I don't know where I can find someone with that capability.

 

[sub-xtx]

Ok, sorry.......
Italy too far........

 

[Mosey]

Italy is never too far!...just for EDM.

 

[Holt]

Come to Denmark, and i will do the EDM for free ;D

Holt

 

[Mosey]

Thanks.
My daughter-in-law is Danish. Her maiden name is actually "Dane"
Maybe I come!

 

[t_ottoboni]

Last time i removed a broken tap from aluminum I used nitric acid. Just put a drop in the hole, wait, clean and then another drop until you can remove the tap. In some places it can be hard to find, but since I had it here, it dissolved the tap in 10 minutes. Nitric acid doesn't attack aluminum, but literally boils steel!

 

[Mosey]

What is the proper concentration of alum powder in water for steel removal?

 

[Sshire]

Failure :'(
Seems like the season for broken 2-56 taps. Since I broke one about 6 months ago, I've been buying better taps (OSG etc) and haven't broken one.....until last week.
I saw this thread, got some McCormick Alum, mixed a saturated solution in warm water and put the part (6061) in a small Pyrex dish and placed it on an electric griddle at 200 F.
End of day 1 no change, couldn't pick even a chip out.
End of day 2. Same negative result.
Went away for a few days on biz. The piece was at room temp for 2+ days
No change. What kind of a magic tap do I have?
Remade the part.
Best
Stan

 

[shred]

What is the proper concentration of alum powder in water for steel removal?

I used as much as would dissolve and then some. Degrease the part and put it in the solution in a jar somewhere you pass by. Shake jar every time you pass it. After a few days I was able to pull out the broken bit.

 

[techonehundred]

I used a ceramic skillet and put it on the stove. keep it just under boiling. The alum and water mixture will create a stream of bubbles from the tap(iron). I dissolved an 8-32 tap in 3 hours.

 

[ninefinger]

try using pickling vinegar and alum - it worked much better for me than water and alum but it had to be boiled as well. Solved my broken 2-56 tap issue as well as my broken #40 drill

You may want to test the boiling vinegar & alum on a scrap piece of aluminum first - I had some minor dulling of the surface but nothing remarkable.

Mike

 

[Mosey]

After several days in the alum, nothing. So, now the head is in a simmering hot bath of alum and vinegar, with bubbles coming out of every orifice, bolt holes, intake ports, exhaust ports, valve guides, and, even the hole with the broken tap in it! Keep you posted. Bad odors, too.