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Broken tap removal

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Airpirate

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#1
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.
 

Bob Korves

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#2
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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Technical Ted

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#3
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
 

benmychree

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#4
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.
 

Airpirate

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#5
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?
 

PT Doc

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#6
sorry to hear about that.
 

Technical Ted

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#7
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
 

Bob Korves

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#8
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.
 

Airpirate

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#9
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.
 

benmychree

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#10
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.
 

Airpirate

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#11
Got it. I ordered an M35 cobalt spiral fluted 6-32 tap so I hope if I take it easy and keep it clean I should be ok the rest of the way.
 

gradient

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#12
Saw a note sometime back (possibly on this site) that freezing the tap with freeze spray then hitting it sharply with a pin punch will shatter the tap. You can then pick out the pieces. Freeze spray is available through any electronics outlet such as Digi-key. Broke a few 4-40 taps and this worked.
 

Airpirate

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#13
Interesting. A little liquid nitrogen perhaps.
 

Airpirate

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#14
Still wondering the price range to EDM this out. Anyone have an idea?
 

petertha

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#15
I went through similar pain with M3 tap in blind hole in aluminum (model radial engine crankcase). I had some hours into the part so went down the path boiling alum solution. It worked on Youtube so it must be true LOL.... alas but not on my tap. Happened to be a high quality chip ejecting tap & maybe the coating vs. plain HSS messed with the alum not working. Long story short the piece was wrecked in the process. You don't even have this option with steel.

Later on just for interest I peck drilled on it with an oversize carbide endmill. It was tough going but eventually removed the material. This would only be an option to then insert plug the hole & re-tap or maybe weld or something. Suspect EDM would be the best if it was cost effective.

BTW - this particular problem was my fault. Miscalculated the overhole too shallow vs tap depth. Even though it was chip ejecting, torque controlled tapping head, proper fluid.... shrapnel, especially sticky aluminum swarf, can tighten things up within a half turn & then its too late. Now for the critical holes in teeny sizes I use my own tap holders. Just made from O1 tool steel, slide in a collet at same drill position. A bit slower but they work perfect. You can feel torque & cutting pressures. Also get in the habit of blowing any chips out with compressed air & cleaning the tap before re-entering the hole on consecutive (tap cleaning) runs in the hole. Agree on quality taps & not skimping on used/dull taps. It wont solve all your problems but at least will eliminate some common ones.
 

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Glenn Goodlett

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#17
Funny, I couldn't get the alum thing to work either. Scrapped the part.

Life is better with quality taps.
 

rwm

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#18
One thing I have done to save a part is to TIG weld the area of the hole. If it is not too deep you can create a puddle that alloys the tap fragment in to the surrounding steel. Then you can easily drill and tap the same location. This technique only works in some situations. The fragment cannot be more that about 1/4" deep and you have to be able to accept the distortion caused by welding. You may need to enlarge the hole above the tap fragment. Then melt the tap fragment, then use filler to get a flat surface. It can be done with good cosmetic and reasonable metallurgic results. Oh yeah, and it's cheap!
Robert
 

Airpirate

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#19
Mine tap is too deep for this process I believe plus I don't have a TIG welder but I appreciate your input.
Thanks
 

tq60

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#20
Go to harbor freight and get the small pneumatic hand piece die grinder and a pack of the diamond burs.

Get a few packs.

Lots of lube and air blasts and you can get it out.

Think like a dentist.

We have done this a few times.

If drilling holes with drill press then tap as next action before moving part.

Loosen motor drive so you can turn Chuck by hand.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 

pontiac428

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#21
If you were using a straight-flute tap, the Walton extractors are the way to go...
 

stupoty

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#22
Often you can get thread taps in a set of three, taper tap / second tap / bottoming tap

I have found it helpful to use the taper tap first to aid with both alignment and the extra taper helps with a low cutting force to start with.

I use an old tooth brush to remove chips from the taps between holes also :)

Stu
 

Airpirate

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#23
If you were using a straight-flute tap, the Walton extractors are the way to go...
I have a number 6 Walton extractor but the blades won't fit between the flute and the hole threads.
 

Airpirate

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#24
Filed the Walton fingers until they fit, then broke them off while trying to extract. Going to try freeze spray and a punch and then EDM.
 

pontiac428

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#25
D'oh! HeliCoils will work nice, but first you gotta get that tap out. I had a similar problem a while back (extractor broke deep down) and drilled it out with a diamond bit. In the end, it was okay...
 

Jimsehr

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#26
Look on you tube for Jerry’s tap extraction . It will show you the way it’s done. And he has people send him parts from all over the country to repair. He is in Santa Ana Ca. And he will be able to tell you the cost.
 

Airpirate

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#27
Thanks! I'll check it out
 

BaronJ

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#28
Hi Airpirate,

I've never broken a tap myself, but know a few people who have ! I rescued one job by using a diamond core drill and removing the broken tap and a plug of the parent metal. I turned a plug a thou over size and hydraulically pressed it into the hole. This was then re-drilled and tapped.
I did a similar repair on a broken cylinder head stud, but using a diamond core drill not quite the same size as the stud. That one left the threads in the hole which were removed with an easy out after blasting some heat at it.

So using a diamond drill might be your answer.
 

Airpirate

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#29
Thanks for the tip. The oversized plug action is also a good suggestion.
 

ThinWoodsman

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#30
Broke a 6-40 tap off when tapping DRO mounts on a Taig mill. Tried a few of the usual methods, then ended up using a carbide grinding burr to get a hole started, then using an Omega drill to get all the way through the tap do I could pull it out in pieces. This was freehand using a hand drill on the horizontal plane, so it took ages - but it did finally succeed. Those 6-40 and 4-48 holes don't leave you a lot of room to work in.

Learned my lesson from that and bought the full 3-piece tap set instead of trying to use a taper for everything.
 
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