Author Topic: Broken Tap Removal???  (Read 22706 times)

Offline powderhorn01

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Broken Tap Removal???
« on: October 19, 2013, 12:02:00 AM »
I have a broken 6/32 tap, about 1/2" deep in a thru hole, material is O1 tool steel. I understand that if it were a bronze, or similar, I could toss it in Alum and eat it out. Any ideas for getting it out, poormans homebrew edm, acid, or ??? It is a part for a model steam locomotive, Stevenson valve link. I would really like to save it, as I have a lot of time in it already.
  :bang:
Any thoughts, or help, would be appreciated.
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lordedmond

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Re: Broken Tap Removal???
« Reply #1 on: October 19, 2013, 06:56:05 AM »
 carbon steel or HSS tap

if HSS you are in deep do do ddm is possible

if its carbon steel tap heat the part to red heat and let it cool ( if you have a BBQ light it up and toss in the part leave it online till next day ( i.e. cool very slowly in the ashes ) and you may be lucky and it will have softened enough t drill out with a carbide drill


for lightly loaded threads try using less thread depth ( bigger drill by about 0.1 mm bigger

btw how big is a 6/32 tap anyway

Stuart

Offline John Rudd

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Re: Broken Tap Removal???
« Reply #2 on: October 19, 2013, 10:06:27 AM »
6/32 is around 1/4 inch in English money...
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Offline John Rudd

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Re: Broken Tap Removal???
« Reply #3 on: October 19, 2013, 10:08:06 AM »
6/32 is around  1/8 inch in English money...
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Offline angus

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Re: Broken Tap Removal???
« Reply #4 on: October 19, 2013, 10:09:33 AM »
i used to be able to borrow these sorts of things from work
http://www.waltontools.com/products/remvtap.htm

sometimes worked, sometimes ended up with the tool busted in there!!! :doh:


lordedmond

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Re: Broken Tap Removal???
« Reply #5 on: October 19, 2013, 10:51:08 AM »
John I am more confused now before I asked the question   :Doh:

Stuart

Offline awemawson

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Re: Broken Tap Removal???
« Reply #6 on: October 19, 2013, 11:01:24 AM »
I'm not conversant in American thread specs. Is that 6/32 32 threads per inch on a 6 guage ?

Andrew
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Offline SemiSkilled

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Re: Broken Tap Removal???
« Reply #7 on: October 19, 2013, 12:09:21 PM »
You're right, it does look easy when its finished.

Offline dsquire

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Re: Broken Tap Removal???
« Reply #8 on: October 19, 2013, 12:10:05 PM »
Gentlemen

 :doh: :doh: According to the Machinist Handbook, 11th edition, published 1942, page 1266.
 
6-32 is 0.1380 inches Major diameter and 0.0974 inches Minor diameter. The pitch diameter is 0.1177 inches

This was known as the United States Standard but since 1935 has been known as American Standard Screw - Course-thread Series.  :D :D

Cheers  :beer:

Don
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Offline awemawson

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Re: Broken Tap Removal???
« Reply #9 on: October 19, 2013, 12:31:32 PM »
I bet it's the coarse thread series unless it's perhaps a training course  :lol:
Andrew Mawson
East Sussex

Offline mklotz

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Re: Broken Tap Removal???
« Reply #10 on: October 19, 2013, 12:41:05 PM »
I bet it's the coarse thread series unless it's perhaps a training course  :lol:

Yeah, and "guage" is a small town in Kentucky.

Quote
I'm not conversant in American thread specs. Is that 6/32 32 threads per inch on a 6 guage ?

The numbered screw formula is:

MD = 0.060 + 0.013 * N

where:

MD = major diameter in inches
N = screw number (0,1,2,3,4,5,6,8,10 ... 12 and 14 found in some very antique equipment).
« Last Edit: October 19, 2013, 01:22:27 PM by mklotz »
Regards, Marv

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lordedmond

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Re: Broken Tap Removal???
« Reply #11 on: October 19, 2013, 12:50:00 PM »
Thank you gents the fog has lifted somewhat


anyway to the OP have you got that pesky tap out down the small hole

Stuart

Offline unc1esteve

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Re: Broken Tap Removal???
« Reply #12 on: October 19, 2013, 03:33:06 PM »
One of last year's winter projects was a small EDM (tap buster) for just this situation.
http://homebuiltedmmachines.com/index.php?page=home
Works well but I want to re-do the electrolyte pump.
Were you closer I would give you access to the machine.

Offline oldgoaly

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Re: Broken Tap Removal???
« Reply #13 on: October 19, 2013, 05:48:35 PM »
I have a Rocklinizer that deposits tungsten carbide to tool steel, at one time they made an attachment for a small EDM. The main unit is a power supply, the depositor is a vibrating handle, figure you change the electrode and reverse polarity? But before I try that would like to know more info! there is one on ebay way to high price! http://www.ebay.com/itm/Rocklinizer-500-Electric-Charge-Generator-with-EDM-Router-Model-9750A-/330660662115?pt=US_Heavy_Equipment&hash=item4cfce94b63
My Rocklinizer is a 600 a larger unit.  A long time ago HSM or PIM did a series on a diy EDM (looks like I'm type alphabet soup!) About what year was that??

Offline Jonny

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Re: Broken Tap Removal???
« Reply #14 on: October 19, 2013, 07:22:40 PM »
Just break whats left of the tap in the hole, works every time.

Offline unc1esteve

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Re: Broken Tap Removal???
« Reply #15 on: October 19, 2013, 08:09:11 PM »
Jonny,
Will you explain the break whats left of the tap (without damaging the part) procedure?  And the tools used?
Thank you.

oldgoaly,
I have had severe asthma all my adult life.  The price of the Rocklinizer put me into a acute attack.

Offline oldgoaly

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Re: Broken Tap Removal???
« Reply #16 on: October 19, 2013, 08:50:46 PM »
Unc,
that price is 500+ bucks off the original asking price!  :bugeye:

I broke a tap off and have join the hunt for a tap zapper or making one of these work.
Rocklin the EDM looks like part of a portable drill press for the stand, the working mechanism is like a tattoo machine.
I also have a 314 I'll attach a couple of pics so you can break it down electronically. I replaced one cap on it metalized
polyester type. 

Offline vtsteam

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Re: Broken Tap Removal???
« Reply #17 on: October 19, 2013, 09:21:03 PM »
Last broken tap I had, I lucked out. hit it a few times with a punch and then rotated a super magnet over it -- that unscrewed a few bits, and it was then clear. It was in an aluminum casting however, and the broken tap was close to the surface.

I saw a broken stud removed in a HSM article by laying a nut over the hole and welding through the nut hole a plug weld to the stud. Then the nut became the bolt head and the stud was unscrewed -- the heat and cooling from the weld supposedly also helped loosen the stud.

6-32 is way too small for that method, I guess.
I love it when a Plan B comes together!
Steve
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Offline sparky961

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Re: Broken Tap Removal???
« Reply #18 on: October 20, 2013, 12:36:30 AM »
It may be a bit small for the job, but I have to second the idea of smashing it to bits in the hole. I have had luck with a cold chisel and another tap ground to a point. Take your time and smash little bits at a time off. You may find if through hole that at some point you can force it through. It may damage the hole a bit but it can usually be chased later and still hold a fastener.

Offline Fergus OMore

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Re: Broken Tap Removal???
« Reply #19 on: October 20, 2013, 05:33:56 AM »
Isn't it great to enjoy a laugh? Seriously, there several ways to try( being the operative word) to do it.

One is to make a little dam with Plasticene or similar and put in nitric acid and stir the chemically changed bits out. It's long and tedious and-- you may not have a tiny drop of the stuff needed. Again, you can wedge a three fluted tool to fit the broken flutes- and chance your luck by twisting it loose. Again, you can use an arc welder or mig/mag and carefully weld an extension and go from there. Again, you can use a tiny carbon arc and destroy the core of the tap. Sheer bloody brute force is an added skill.

Again, you can throw the thing at the neighbours cat and make another one.  Of course, you could regrind the next worn tap- which quixotically be blunter than the one which broke in the first place.

Regards

Norman

Offline PeterE

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Re: Broken Tap Removal???
« Reply #20 on: October 20, 2013, 05:47:36 AM »
Since it is a through hole I would try to clrear the tap flutes from the un-threaded side using a har steel pin or wire and a small hammer. Fiddly work yes, but if the flutes are cleared it may even be possible to use a couple of steel wires to un-screw the tap afterwards.

BR

/Peter
Always at the edge of my abilities, too often beyond ;-)

Offline DMIOM

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Re: Broken Tap Removal???
« Reply #21 on: October 20, 2013, 06:24:24 AM »
Since it is a through hole I would try to clrear the tap flutes from the un-threaded side using a har steel pin or wire and a small hammer. Fiddly work yes, but if the flutes are cleared it may even be possible to use a couple of steel wires to un-screw the tap afterwards.

BR

/Peter

That's effectively how a Walton tap remover works, but with the addition of supports (both internal and external) to minimise the chance of the pins shearing. Photos are of a 3-pin 5mm tap remover, hope you can see enough detail .....





With these, you :
  • Clear the debris, then inject lube
  • Slide the pins down into each flute
  • Slide the central core pin down until it touches the core of the broken tap to keep the pins at the right radius
  • Slide the body down until its on the workpiece to minimise the free length of the pins
  • Jiggle to & fro with a tap wrench ...
Dave

Offline unc1esteve

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Re: Broken Tap Removal???
« Reply #22 on: October 20, 2013, 12:44:06 PM »
The recommended tap drill size for a 6-32 thread is a #36.  This is equal to 0.1065" or 2.71 mm.  Small indeed for the welding, heating,  bashing or wiggle, jiggle methods.

Can the hole location be moved?  Can it be changed to a larger size?  I have tried everything my limited brain power could come up with to solve similar situations.  The two solutions that I have found that will work are EDM or making a new part.

The dull tap test is very effective, the dull one is the tap that just broke.  Whenever I have tried the bashing method I have always had the same results.  Both the 'basher' and the 'bashee' were damaged beyond use and a new part was needed.  Perhaps flyingtractors has the proper cold chisel in his collection.  Would that require a larger or smaller hammer?  (OT, what is a flyingtractor?)  The wiggle, jiggle tools belong in the same category as neck ties and high heel shoes.  The hole size prevents the use of the left handed, self removing drills.  A little online research will find some one time use EDM set ups that may help, such as the one that uses a door bell solenoid.  Use this only when unwanted guests are expected.  I have had no luck with chemicals as the errant tap is always of the wrong metal broken in the wrong metal.  CH3CH2OH, in certain quantities, will help all of the mentioned processes.

I live in a rural area.  There is a very rude black cat that travels my yard in the dark on occasion.  He is not impressed with me even when threatened with extreme termination by use of explosive projectiles.  The next time I break a tap I shall seek his assistance first.

Offline DMIOM

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Re: Broken Tap Removal???
« Reply #23 on: October 20, 2013, 02:04:39 PM »
The recommended tap drill size for a 6-32 thread is a #36.  This is equal to 0.1065" or 2.71 mm.  Small indeed for the welding, heating,  bashing or wiggle, jiggle methods......

If by "wiggle, jiggle" you're referring to the proper Walton extractors, I must admit that I don't understand your "The wiggle, jiggle tools belong in the same category as neck ties and high heel shoes.". I've got a set as insurance when I've got a job I'm finishing against pressure - and they just work. I haven't had to use them often, but you just drop the tool in, loosen the tap by rotating a little in either direction & then just back the broken tap out; and in terms of sizes they go down to a US #4

Dave

Offline Jonny

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Re: Broken Tap Removal???
« Reply #24 on: October 20, 2013, 03:10:13 PM »
Chances are that if the taps broke off in the hole its going to need as much if not more torque to unscrew. This rules out screwing them out.

Done loads over the years from 9BA to M16 usually HSS taps.
Bare in mind most of these busted taps were from a workmate in an irreplaceable part measured in 5 figures if had to replace.

Need something hard, now swings and roundabouts whether use softer than the HSS tap or not. Sods law if use something hard that breaks up without marking the busted tap. Use something soft it will bend up and deform, sharpen it up to a needle. Try and shear away one flute then another. Tap may break up in multiple layers in depth.
Just keep plugging away giving it some by whacking the tap with something.

It may damage the thread but what other alternative have you got, touch wood never scrapped a part yet even in softer aluminiums, various steels and titaniums.
Worst was a blind deep threaded hole ie 9BA 1/4" deep to the bottom, it can be done. 7BAx5/8" deep with 1.5mm meat surrounding to normal through tapped holes of a decent size. 3/16" and above its far easier and can see what your doing.
Might pay to keep changing direction if through hole and if can break one flute off it may unscrew from either direction.