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Extracting A Broken Tap


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Have a little bit of a problem here. Snapped a #4 tap inside a blind pocket that is over 2" deep (the pocket, not the tapped hole wink.gif ). The tapped hole is only about .100 away from the wall of the blind pocket so there is no way to mill it out. Tried the Walton Brand extractor, but just can't get it. The part is way too big to stick in the EDM... I have heard of an adaptor for a Bridgeport type machine that works similar to an EDM (without the fluid headscratch.gif ) to burn out the broken tap. Anyone familiar with something like that? Will it arc and fry my A$$?

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I've seen the attachment for a bridgeport, but it's been a real long time. I remember there being fluid flooded onto the burn area though. I'm sure it's a little messy, but it will get the trick done.


What is the material? If it happens to be aluminum, I think there is a chemical that will actually eat the tap without hurting the aluminum. Again, I am remembering this from a long time ago.


I just did a search, and here is a little info...


"I use nitric acid frequently to remove broken taps & drills from stainless steels & titanium. Use 1/3 distilled water and 2/3 nitric acid. I build a dam around the tap with modeling clay and use an eyedropper to fill the pocket with acid. High alloy taps will take much longer than M2 HSS taps to dissolve. When you add the acid, the reaction starts. After a while the reaction stops. Remove the old acid with the eyedropper and add new acid. Scratching the surface of the tap with a scribe will often get the reaction going. Nitric acid passivates stainless steel, so there is no damage to the stainless. In titanium, adding some hydrochloric acid (HCL) will help. Hydrochloric acid will attack stainless steel. There is a commercial product called "Tap Out" that works on taps broken off in aluminum also, but with minor damage to the aluminum. I do not know who makes "Tap Out". We got ours from a tool supplier. Using nitric acid on plain steel will just eat up the steel faster than the tap. One note of caution. Nitric acid gives off strong fumes. Do not breathe them. These fumes will also cause surface flash rusting on any nearby steel parts, so do this outside. The cheapest grade of Nitric acid is "Technical Grade". The last time I bought nitric acid, a gallon of "Technical Grade" was $60.00 and a quart of "Reagent Grade" was $60.00. "Reagent Grade" is used by chemists and is of extreme purity which is not necessary for this application."


Maybe that will help you out.


Good luck man. I hope everything works out for you. There's not much worse than losing a part because of a tap, but I've done it, and it hurts.


I've also had a micro-welder weld a stud onto a broken tap, but it sounds like you have a pretty hard area to reach.


Paul McGarr

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Rob send it here it the part is not to big. I had our guy ge ta 2mm tap out the other day out stainless using our Sinker EDM. It was a roll form tap and I thought for usre he was going to kill the part but no problem. All kidding aside find a local Sinker shop and let them get it our for you think most places chager between $25/$55 a part unless you got 20 borken taps then they might want ot charge a little more.


Good luck

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Rob send it here it the part is not to big.

Thanks for the help Ron, but the part is about 60"x40"x4" Not very cost effective wink.gif . The shop that normaly bails us out of these problems can't fit the part on their machine.



Rob, have you considered milling around all sides of the tap untill it falls out of the material?

Can't get an end mill that far down and so close to the wall. To top it off there is an o-ring at the top to seal off the water.

Right now the Tap Out is looking good..

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Under rev a solid carbide slot drill thru the center - you might snap a few of them off but if burning is not an option then this method should work.

That's my standard practice Jack, except I use a carbide ball end mill.



If there is room, can you get a small dremel cutting blade, and grind a straight through it, to maybe get it with a screw driver?

Too much risk involved. Can't have scratches.


Good thing we're a couple of weeks early on the job. Gives me some time to play with it.

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