broken tap

Well, Google so far has NOT been my friend. With a HSS 2-56 tap broken off in a lump of bronze I did my search - found reference to "jewellers' screw remover, a white paste". Looked all over the place in jewellers' webpages and couldn't find a thing. There was recent reference here to the use of alum (septic pencil), but I believe that was for use for a tap snapped off in aluminum. I could move the hole over and retap, but it would throw off the symmetry of the piece - however if the worst comes to the worst. Help! Mike in BC

Reply to
Michael Gray
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I seem to recall from the book "machine shop trade secrets" a procedure for broken tap removal that looked promising. His suggestion was to use a round peice of carbide (in your case, probably 1/16") and grind a spade shape in the end of it. From there, mount it in a mill and VERY slowly feed it into the tap. It will (supposedly) cut right through.

That said, I've never tried this procedure, and 1/16" tool won't be very rigid.

Do you have access to a wire-fed EDM machine?


Reply to
Nick Leone

I used James' Harvey's technique with a 4-flute solid carbide ball endmill, pecking 0.005-0.010 at a time against the quill stop. It made short work of my 1/4"-20 tap, but I wouldn't try it with a tool any smaller. The forces involved in the process far exceed those encountered in ordinary drilling...

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Looking around, there are several hacked-together EDM based tap removal techniques on the web. Here are two that I found interesting:

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Do you think this is applicable in your situation? Ultimatly, it may be less hastle to move over and re-drill.


Reply to
Nick Leone

The jewelers stuff is just alum. Every generation seems to forget the trick and someone capitalizes on this by putting a bunch of alum in little bottles.

They sell a bunch and disappear before the old timers can stop laughing.

Alum works fine on bronze.

Use a saturated solution. You have to keep it hot and the tap immersed. If you can't do either, you are just gonna waste your time.

You used be able to get alum at drug stores, but it is getting harder to find. It seems drug stores don't want to sell anything that doesn't come in a blister pack.

It is also used by textile dyers. Check for places that cater to craft dyers.

And they're called "Styptic pencils"

Paul K. Dickman

Reply to
Paul K. Dickman

it should help immensely by flushing out the crud. You know it is working when a lot of black crud develops - that's atomized metal. You need a method to move the electrode up and down in incredibly small movements. I actually leaned on the head of my Bridgeport as the fine feed, and used CNC feed at .01 IPM or so as the coarse feed. When you get it working right, the electrode makes a sizzling sound, but it is very hard to keep the gap just where that happens.

I have burned out a couple 4-40 taps this way, but it is very slow going. An electronic pulser for this is on my "to do" list, but I don't know when I'll get to it.


Reply to
Jon Elson

Howdja know I did just that with a buddy named Ed about 45 years ago?

We packed the alum in cardboard tubes with metal ends and slide off lids.

The name we sold it under was "Bust Out" and the label featured a photo of Jane Mansfield wannabe with her nice rack protruding from a low cut dress.

Didn't sell enough of it to keep up the project more than a few months, but IIRC we didn't lose any money doing it.

Ed and I moved on to develop and patent a machine for keeping the counter help in pool halls from robbing the owner blind by pocketing cash being charged for pool table rental.

Quite simply, I built a console which had a bunch of switches to control the lights over each pool table individually, and when a light was turned on to let people play a Veeder Root counter (one per table) clicked up the rental charge for the time they played, and that's what they paid when done. A master counter totalized the "clicks" from all the individual meters, and if the cash taken in didn't match what it read for that day the owner knew something smelled.

Thanks for the mammaries,


Reply to
Jeff Wisnia


Recently I was in the same situation having broken a 6-32 tap in mild steel.

In the end I had to drill it out using 3 small diamond drills.

Not a situation I care to repeat...

Michael Koblic, Campbell River, BC

Reply to
Michael Koblic

Reply to

Alum, or Aluminum Potassium Sulphate, when added to water is Sulfuric Acid. Available in flooded cell auto batteries, and in the drain cleaner section of some hardware stores.

Nasty stuff on skin or eyes. I have no idea if it reacts with Bronze, but it does dissolve steel, heat speeds up the reaction.


Reply to
Mechanical Magic

A wire feed EDM isn't gonna do a lot here...the chances of being able to get a wire through, on location, aren't good. AND that's assuming that OP even has a through hole.

Reply to
The Davenport's

"Michael Gray" wrote: (clip) I could move the hole over and retap, but it would throw off the symmetry

^^^^^^^^^^^^^^^^^^^^^ Or you could drill out or core out an oversize hole, and then press in a piece of bronze rod. Thisw would allow you to retap without losing the symmetry.

Or how about heating the piece enough to anneal the broken tap, and then drill it out?

Reply to
Leo Lichtman

What wondrous place is this you live, that commonly has such yesteryear supplies? The local Publix would get cross-eyed if you asked for pickling or brewing ingredients.

Reply to
Richard J Kinch

It firms up your pickle. Karl

Reply to

Alum is used to acidify soil. Check the farm or garden store.

Reply to
Jim Wilkins

On Wed, 9 Apr 2008 03:48:06 -0700 (PDT), with neither quill nor qualm, "" quickly quoth:

Ayieeeeeeeeeeeeee! Touch that to your pickle and it'll retract so far up in your body you'll look like a woman.

-- Save the whales! Trade them for valuable prizes.

Reply to
Larry Jaques

Brewers stuff is mostly in specialty stores in my part of the world. [but there are probably 5-6 within 20 miles]

Walmart carries a complete batch of canning/pickling supplies- and most large grocers do pretty well in season.

I'm near Albany, NY. Publix looks like a southeast US chain-- and no canning supplies? [are you in a city or in the suburbs?]


Reply to
Jim Elbrecht

He said is was a HSS tap.

Carbon tap you could anneal in Bronze. Next time break a carbon one.

Reply to

Taps are steel and are easily dissolved in muriatic acid. Bronze will lose a little tin at the surface (or zinc if it's really brass), but will not be etched away by muriatic. Wear gloves and goggles. Carefully add muriatic acid to the hole. Bubbles of hydrogen gas will form as the tap dissolves. You needn't dissolve it completely - just enough to allow you to screw it back out using needlenose or some such tool. Bruce NJ

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I don't know where you took chemistry but I bet it isnt acredited. ...lew...

Reply to
Lew Hartswick

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