[keen]

Wow - never knew you could dissolve a tap!

I either remove by making a small tool - or use my EDM. The small tool is a little key you make of tap drill diameter, with a cross slot sawed, or filed, or ground to suit the broken tap flute gaps, made out of tough steel eg allen key steel, tapped down over the broken tap, and unscrewed. Usually works and is quicker than EDM.

keen

[BAMCNC.COM]

Keen, any vids on the EDM?

[popspipes]

I mixed about 2 cups of water with 4 ounces of the alum granules, put the mixture in a crockpot with the part, I used the lid to keep the water from evaporating off so fast, the process worked, took about 6.5 hours on the high setting, when checking the part I thought there were remnants of the tap still in the hole, turned out it was the curled chips that were on the flutes of the tap still in their respective positions! It did turn the part grey, but with a bit of effort with a scotch brite pad the color was restored.

I am going to put the mix in a plastic bottle and save for another time, hopefully I wont forget where I put it ha!

The bubbles got more profuse as time went on, I think due to the oil on the tap insulating it at the start.

[Beezle]

That is an excellent idea. Container plus heat and a lid.

[carlowens]

I just tried the alum trick a few weeks ago on this part:



This was a 10-32 tap buried about .6" into the hole, broke flush.

The process did in fact dissolve the tap, but slowly. By the time the tap was nearly gone, the surface of the aluminum had enough damage that I scrapped the part. And I mean physical damage, not discoloration. This process took overnight.

yeah that's why this process is usually the last one chosen when all else fails if tap extractors, picks and the welding rod methods fail and the part would be scrap anyway with the tap still in there. one other option is to use a counterbore with a pilot hole big enough for the tap to go into and bore around it then plug that hole and retap or use helicoil.

[keen]

Keen, any vids on the EDM?

Yeah good idea - next time I get a suitable big non confidential job I should make a vid. Cheers.