Broken Tap Removal???

[flutedchamber]

If a standard tap extractor won't work, I've always had luck with Kroil, then jewelers pliers and patience. 

There are needle nosed ring making jewelers pliers that will grip a 4-40 tap broke below the surface and let you turn it out.  The pliers aren't cheap (being boxed jaw design and made from good grade of steel) but the last for years and ARE actually worth the cost.

Look online under "jewelery repair tools" and other such headings.

[philf]

Have you got a Dremel or high speed micro air grinder? A very small abrasive point or diamond burr might do the trick - even if only to weaken the tap enough to break it.

Phil.

[unc1esteve]

Dmiom,
I was responding mostly to Mr. Omore's post based solely upon my own experience.


Jonny,
Thanks.  It seems I have not tried the correct needle point tool.

[picclock]

I found myself in a similar situation and was able to make a crude spark erosion machine with very little effort. It lacks anything sophisticated, just being a rewound mains solenoid (if you have a 12v one use as is) and a car battery charger. I have only broken two taps, normally by using them when they are past the end of their life.

http://s917.photobucket.com/user/picclock/library/Spark%20erosion%20machine?sort=3&page=1

One end of the solenoid is connected to the battery charger, the other end of the charger to the work, the other end of the solenoid to the erosion tip. I used silver steel cos I had some lying around and paraffin for the liquid. See pictures. The reason it works and is simple is because the height of the electrode is self adjusting. As the electrode makes contact with the work a current flows in the winding which causes the solenoid to pull in. when the contact is broken the magnetic energy stored in the coil collapses, and that causes an arc to occur between the electrode and the work. After the field collapses gravity causes the electrode to fall and make contact repeating the cycle.

Its not very quick but you can leave it unattended - took about 2-3 hours. I chose an electrode size that would erode the core of the tap which it did without affecting the cut threads. Despite the 'design' it appeared to produce mimimal RF interferance, possibly because the spark is shielded by the work.

Hope this helps

best regards

picclock

[mosey]

I once broke a 2-56 tap in an aluminum head. Tried all of the usual extraction methods to no avail., including that dissolve it with alum, extractors, etc. Went down the street to the professional machinist and he put it in the Bridgeport and milled it out slightly oversize with a carbide mill. Then I put in an aluminum plug and drilled and threaded a new thread. Can barely see the plug. Problem solved low tech.
Mosey

[vtsteam]

I found myself in a similar situation and was able to make a crude spark erosion machine with very little effort. It lacks anything sophisticated, just being a rewound mains solenoid (if you have a 12v one use as is) and a car battery charger.

That's pretty interesting! 

[awemawson]

Years back I had a commercial 'tap disintegrater'  that was simple in the extreme. The electrode was carried in the end of the armature of a solenoid. When the weight of the armature brought the electrode into contact with the work, it completed the circuit and the solenoid pulled it back up. So it buzzed away merrily arcing away the tap. There was a little plastic tank with a tap to control the flow (just a steady dripping worked best) of tap water that washed away the debris and kept things cool. I used tungsten TIG electrodes.

[Joules]

Years back I had a commercial 'tap disintegrater'  that was simple in the extreme. The electrode was carried in the end of the armature of a solenoid. When the weight of the armature brought the electrode into contact with the work, it completed the circuit and the solenoid pulled it back up. So it buzzed away merrily arcing away the tap. There was a little plastic tank with a tap to control the flow (just a steady dripping worked best) of tap water that washed away the debris and kept things cool. I used tungsten TIG electrodes.

aw, thats sounds really useful are they still available, that would be a cool project to build.

              Joules

Sorry picclock, not had enough coffee and missed your post...   

[awemawson]

Not seen them for sale other than second hand, but it would be a trivial exercise building one.

[vtsteam]

Andrew, how many volts was that system supply? Was it battery powered or mains? Seems like for very occasional use, a battery powered version would be ideal, if possible.

Tempted to build one. I don't have a broken tap (uh, right now), but it just sounds like a fun project. And it would be nice to have it already made up when I need it rather than being an emergency project, or a wished for one.

[drmico60]

Vsteam, I went down a similar road to Andrew and built a similar spark eroder to remove broken taps. I took the development a little bit further. The apparatus is descibed in detail here:
http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html
and here:
http://mikesworkshop.weebly.com/a-spark-erosion-apparatus-mk-3.html
Mike

[awemawson]

It was 24v AC - just a simple transformer off the mains. It's working just like an ordinary bell, except instead of the contacts you have the work & electrode. But good enough to break up the bits of a tap - oh yes I've broken taps 

Obviously pretty crude, and not a patch on a proper edm that controls the discharge and immerses everything in a dialectric fluid designed to hold off the discharge until the last microsecond. In a proper edm the dialectric expands and collapses explosively hundreds of thousands of times a second producing ultrasonic cavitation.

[unc1esteve]

Powderhorn, Jonny,

Video of EDM tap removal using hardened punches.