Drill Removal

Rockytime

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I broke off a #57 drill in a model engine cylinder. I need to dissolve the drill. I do not like use muriatic acid as it is nasty to tools and things if it leaks vapors. Anyway I never use acids. Vinegar is slow. Anything else that works?
 
not knowing exactly how the drill is broken, and what material the bit is broken off into, limits my response to mere conjecture, but here it goes...
if you can open the top of the hole with a slightly larger drill or endmill- down to the depth of the broken bit, you may be able drill, invert the part, and tap on the backside.
the broken bit may fall out, or at least be more accessible for a pick or left hand drill to extract the broken section.
you could then possibly tap the hole to accept a piece of allthread and re-drill the hole back to the original spec size, or possibly simply retap the hole and use a larger fastener for that bore.
 
See if you can find some Tapout. It's made primarily for tap removal, but no reason it wouldn't work on drills. It's a mix of acetic, sulfuric, and nitric acids. It does work. I have saved many a part with it. Just follow all the cautions.
 
I'm guessing since we're discussing this there's no part of the drill bit above the surface. I'm not sure if you have a TIG welder, but I sharpen the tungsten, hit the foot pedal and stick it to the drill bit, then pull gently and turn. I know .043 is a small hole to operate in. If you don't want to use acid then EDM is my second suggestion.
 
Folks in the watch repair world use Alum to dissolve steel screws from non ferrous metals.

David

Thank you David,
Alum was what I was hoping to remember. I don't do watches, only clocks. I'm too old for watches as it is a different discipline. The drill is a #57 and too small for mechanical methods. I find I have alum on one of my benches and had forgotten all about it. Thank you kindly for the reminder. BTW the drill is in aluminum.
Les

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Hi Les,

I work on clocks as well, no watches. I have heard Alum mentioned many times in my other forum. User friendly, readily available and as I recall works better , ie quicker if heated .

Let us know how you make out, since I have never had to use it myself.

David
 
Just finished removing the small broken drills. Can't believe how fast alum works. Of course the drills were very small but I soaked the cylinder in an alum solution at 9:00 am this morning and by 5:00 pm the drills were reduced to mush and I poked out the residue with a small wire. Unbelievable. The cylinder is for Elmer Verburg's little geared engine.

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