# Drill Removal



## Rockytime (Apr 9, 2017)

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?


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## francist (Apr 9, 2017)

Removed unreliable content.

-frank


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## Ulma Doctor (Apr 9, 2017)

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.


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## Tony Wells (Apr 9, 2017)

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.


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## David S (Apr 9, 2017)

Folks in the watch repair world use Alum to dissolve steel screws from non ferrous metals.

David


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## Rustrp (Apr 9, 2017)

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.


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## mikey (Apr 9, 2017)

Can you drill a hole on the bottom of the cylinder and tap out the drill, then weld the hole shut?


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## Rockytime (Apr 10, 2017)

David S said:


> 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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## David S (Apr 10, 2017)

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


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## Rockytime (Apr 10, 2017)

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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## francist (Apr 10, 2017)

That's great to hear, and thanks for letting us know of the success.   Did you heat the solution or just use it at room temperature?

-frank


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## Rockytime (Apr 10, 2017)

Just room temperature.


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## olstrat (Apr 15, 2017)

Where can one get alum?


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## David S (Apr 15, 2017)

You can get alum just about anywhere.  Walmart carries it.  It is used for preserving food.

David


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## olstrat (Apr 15, 2017)

Thanks David


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## Silverbullet (Apr 15, 2017)

You don't remember the three stoogies. They used it in a punch drink for a bridge party . It's a lip puckerer ,also used to be used by women as a female cleaner . YUPP I ain't saying.


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## Tozguy (Apr 15, 2017)

Barbers used to use an alum stick to stop razor nicks from bleeding. Didn't know it does taps too. Good to know, thanks.


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## MetalMuncher (Apr 16, 2017)

I'd like to learn more about this process, having just recently broken a 4-40 tap in a cast iron mini-mill base. Fortunately, the power feed safety stop switch I was mounting could be relocated. Why doesn't the Alum also dissolve the surrounding material holding the broken bit or tap? What kinds of metals will Alum dissolve or not dissolve? I've never seen what happened to that tap happen before. It was a spiral flute tap (it's all I use once I discovered them!) and it was going in fairly easily with lubricant, held straight with a tap guide block. After several turns I decided to back out and clean out the tap so I could proceed deeper. When I tried to turn it in reverse, it bound up, and while very gently twisting it back and forth to try to free it up it snapped off. First one I can remember breaking during removal. I'm thinking the casting may have had some impurities in that spot.


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## David S (Apr 16, 2017)

I believe the Alum trick only works if the item to be removed is ferrous and it is in non-ferrous material.

David


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## mcostello (Apr 16, 2017)

Tried it once and it did not work, figured tap might have been slightly different recipe. Simmered on wood stove for a week with a saturated solution.


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## Highsider (Apr 16, 2017)

I hate to admit that I had anything to do with this, but when I and my friends at the shop were all young and foolish, one of the guys broke off a 5/16  drill bit in a deep hole into the end of a roughly 4" Dia. shaft. 

   About a half inch was protruding from the shaft, so he tried to get it out with vise grips. He made about another half inch of progress in working the bit backwards out of the hole before the bit broke again, this time well below the surface.  It was a large industrial gearbox shaft and he had it all finished except for the grease channel  he was trying to drill.  Rather than scrap the expensive piece he decided to do something rather foolish to salvage the project.

We gathered the 2 broken pieces of drill bit that we had and added the lengths together then comparing that to a complete bit that size.  This showed us that the hole was deep enough in the shaft if he fudged a bit on the location of the cross drilled hole where the grease would eventually come out.   He went ahead and cross drilled the shaft in that location, threading the outer end of the hole for a short depth for a bolt thread temporary plug.  Then he drilled a fuse hole thru the center of the bolt.   You can see where this is going can't you?

The following morning,  he used a splinter of wood to pack the cross hole with black powder.  He carefully screwed the bolt finger tight into it's hole and pushed a piece of cannon fuse into it.   With the shaft laying across the pan of his lathe and with the offending end pointed toward the roll up door, he lit the fuse and we all ran for the doors.

It was noisy, but not as much as I had expected.    There was some funny smelling smoke in the shop for a little while 'til we aired it out and a broken drill bit driven almost all its length thru the roll up door (which was made to quickly disappear), but within a couple of minutes no one could tell anything untoward had happened.  

And yes the shaft was salvaged.     *I do not recommend this unsafe action to anyone!!!*


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## Rockytime (Apr 16, 2017)

Please recall the drills which I removed with alum were #57,  .o43 diameter. Very small. If I were to try removing a 1/4-20 tap I would do something different. Don't know what but surely different.


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