Broken tap removal

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Airpirate

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I snapped a 6-32 tap off in annealed 4140 steel. I was threading a bottoming hole but stopping over a 1/4 inch from the bottom.
I cut a bit backed off cleaned etc but the tap broke off buried in about 1/2 and broken flush with the work.
I bought a Walton #6 broken tap removal tool but the blades won't fit in the flutes so I assume I ordered the wrong size (eBay, seller couldn't tell me anything regarding fit) .
Anyone have experience with the Walton broken tap extractors? Do they work? What size for a 6-32 screw?
Any other suggestions on removing the broken tap.
Thanks for any suggestions, I've been working on this project for over a year and would really like to salvage it.
 
If you really care about the part, I would take it to a local shop that does EDM work. They certainly can do that for you. I do not know what the cost is, but it should not be more than the value of your valuable part. They can take it out and save the threads at the same time.

After it is out, do some studying, here on this forum and elsewhere, and find out how to use small taps on tough steel effectively and without breaking them. The short answer is a NEW high quality spiral flute tap, excellent cutting fluid for the job, and using the tap with the proper technique. 6-32 is about the worst size for breaking taps, and annealed 4140 is one of the most difficult metals to tap without problems for a newbie (work hardening.)
 
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I agree with what Bob says. If you want to try, I've gotten taps out by very carefully working them back and forth with a small punch. I have also inserted small diameter pieces down in the flues (similar to the fingers of a tap extractor) and held the tops together and then put a screw driver between them and work the broken tap back and forth and gotten them out.

A lot depends on how lucky you are...

I've never had much luck with tap extractors.

Ted
 
The Walton tap removal tools are just marked with (only) a number on the sliding sleeve; sometimes there is the option for 2,3,&4 flute taps as to the number of fingers used and the shank and sliding sleeve; I don't have a catalog to be able to say what the options are, but they should be available online, and I don't have a #6 to look at. If a tap has simply broken off, these will usually work, first clear all chips from between the tap flutes, one of the fingers usually works to do this; if there is any tap still showing above the work surface, grind it off, then insert the fingers in as far as they will go, then slide the shank down as far as possible, then slide the sleeve down against the work, then attach the tap wrench and with a good tap lubricant applied, work the tool back and forth with comparitively light pressure until the tap is loosened, gradually turning further and further until it is possible to back the tap out. That being said, it works if the tap has simply broken off, if it is shattered in the hole chances are poor for removal by that method. EDM is about the only way under that circumstance.
 
Thanks all. I have ordered a spiral fluted 6-32 tap from Tranvers. I expect it will be better than the Home Depot and lowes variety. I have successfully tapped 6 of these holes so far but was thinking of slightly over boring the hole. Calls for a #36 but maybe I might try a 34 then I won't be binding the threads against the bottom of the cutter grooves and the screws are stainless into 4140 so I think the threads would be sufficient. Thoughts?
 
I would suspect that taps from Home Depot and other hardware type stores might very well be carbon steel taps. I would not use taps of this material for 4140 or even steel for that matter... I do have sets of them, but use them only for cleaning up threads that already exist; not for tapping new threads.

I suggest using a good quality HSS tap only. Stick with good brands made in the USA. This will help keep you from breaking them, especially the smaller sizes. Also, make sure you use a good tap handle and not a regular wrench to tap since the sideways pressure is sure to break taps.

Just my two cents,
Ted
 
The oversize drill will help a lot, just make sure you do not need ultimate strength from the bolt. I have never had a problem with using a mildly oversize tap in tough situations, and the slightly larger hole size will still give you better than 50% of the optimum strength of the 6-32 fastener. I think I would use a #35 drill, only .001" smaller than #34. Those few thousandths larger hole will make the tapping a lot easier.
 
I found an EDM company where I live, any idea what they might charge to burn out my tap?
I'm more concerned however that they might not have time for a little job like mine.
 
Most tap drill charts are for 70% thread depth, so it is unlikely that the tap so binding along the roots of the thread on the tap are quite unlikely, a few more thousandths larger tap drill size is not likely to make much difference.
 
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