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Broken tap

Broken Tap help please

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Dave C05/12/2010 18:54:09
102 forum posts
37 photos
Help after spending a long time making a particular part I have managed to break a 1/8 x 40 tap in the thing, Apart from the lesson learned of doing the tapping as early on as possible before all the easy shaping etc I would also need some help to get the thing out again.
The tap is about 3/16" deep and is HSS (I think) into BMS
I really dont fancy making another full part so if there are any Ideas for me to try first it would be greatly appreciated ! !
Dave
GERALD EDWARDS05/12/2010 19:05:48
3 forum posts
DO WHAT WE DO AT WORK  GET CARBIDE CUTTER AND USE IT AS A DRILL FAST 1000RPM+ STEADY PRESSURE IT GOES THROUGH LIKE BUTTER IF YOU HAVE AIR LINE BLOW ON IT THEN PLUG THE HOLE AND REDRILL AND TAP IT
Dave C05/12/2010 19:28:48
102 forum posts
37 photos
Now for the next beginers question. You say carbide cutter but what profile etc should I use as I have never attempted this before.
Many thanks
Dave
JasonB05/12/2010 19:30:36
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25215 forum posts
3105 photos
1 articles
Carbide 2 flute slotdrill as these are endcutting.
 
Sometimes you can pick them out with teh end of a scriber or a couple of hard pins down the flutes and a small rod between to act as a tommy bar, does depend on how tight the tap is stuck
 
Jason

Edited By JasonB on 05/12/2010 19:31:04

Edited By JasonB on 05/12/2010 19:32:41

Ramon Wilson05/12/2010 19:54:42
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1655 forum posts
617 photos
There is a home produced alternative David, especially as the tap is not too deep.
 
You could make a hollow cutter from silver steel and providing you can position it accurately over the axis of the broken tap you can mill the metal from around the outside.
 
The OD of the cutter should be as small as you can get away with perhaps 5mm in this case. Cut the teeth with a triangular file and H&T. It is a slowish process but by it's nature quite controlled. As you are quite shallow you will probably not have to go far before the tap will loosen. The cutter does have to be continually withdrawn to clear the swarf and of course it does leave a larger hole. Don't debur this hole.  Loctite in a small slug and peen it over then machine off before re-drilling - possibly you still have plenty of depth of  the original hole left to take the strain.
 
I have used this method - it does work and has it's drawbacks as stated but you need nothing more than a bit of silver steel and the means to harden it.
 
Good luck which ever way you choose - it can be a very awkward set back but not unsolvable.
 
Hope this helps in some way,
 
Regards - Ramon
Stub Mandrel05/12/2010 19:57:47
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4318 forum posts
291 photos
1 articles
If you have some 3/16" to 1/4" silver steel, drill a bit out 1/8" and file some cutting teeth on the end. Harden and temper and use it to carefully drill out the material around the tap. You can then plug the hole and try again.
 
Neil
GERALD EDWARDS05/12/2010 19:57:49
3 forum posts
JUST A NORMALY CARBIDE 3 FLUTE SLOT DRILL WE USE MR CUTTERS I WOULD NOT GO UNDER 4 MM DIA 
GERALD EDWARDS05/12/2010 19:59:28
3 forum posts
MAKE SURE DEAD CENTRE OVER THE BROKEN TAP
Dave C06/12/2010 10:39:35
102 forum posts
37 photos
Thanks for all the help guys, Its very much appreciated !
Dave
Terryd06/12/2010 11:00:13
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1946 forum posts
179 photos
Thanks for that tip Ramon and Stub,
 
Doh!  After all these years of broken taps and scrapped work I never thought of the obvious easy and cheap solution, especially if the plug can be soft soldered in, I'm of the old school and just don't seem to be able to trust glue!  
 
Hi Gerald,
 
Just a word of advice, All capital messages are considered rude on the internet (and in emails) it is considered to be the equivalent of shouting at someone.  On some forums it would not be acceptable.
 
Best regards
 
Terry

Edited By Terryd on 06/12/2010 11:05:05

Ramon Wilson06/12/2010 15:15:18
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1655 forum posts
617 photos
Hi Terry
 
Yes so was I until I tried it buuuuuut.... 'you need the right type in the right application with the right clearances' for it to be at it's best
 
For most occasions that I use it in preference to solder, either soft or silver, it's because no heat is required but like so many other things 'yer pays yer money' etc. I can say though that where I have used it so far over several years it is, as yet, to let me down - I suppose it can't be said fairer than that.
 
(BTW Haven't forgot the pics - just doing something at the mo will send them when finished)
 
Regards - Ramon
Johan van Zanten06/12/2010 16:16:04
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52 forum posts
98 photos
Hi Dave,
 
I can spark erode the tap for you. Most of the time the work has no damage and you can just schrew a bolt in the hole. I will do it for free but you have to sent the pice to the Netherlands. Perhaps I hear from you.
 
Regards,  Johan.

Edited By Johan van Zanten on 06/12/2010 16:17:16

James fortin06/12/2010 17:06:29
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46 forum posts
12 photos
i once read that spark erosion was partly discovered in the russian ship yards as they used to weld an extra piece of bar to a broken tap or drill and unscrew it via the welded piece, but they noticed that when they welded it the spark eroded the metal and so EDM was born.
 
you could try zapping a rod to it with a welder? 
 
many thanks
 
james 
 
 
James Fair07/12/2010 09:16:18
3 forum posts
This comment may be too late now, but in the aircraft maintenance trade, we have what is called a 'tap remover'. There are four steel fingers attached to a T-handle, and a sliding collet which surrounds the fingers. In use, the fingers are inserted into the flutes of the tap, and the collet is slid down to capture the fingers as close to the tap as is possible. Then the fun begins; twisting and rocking on the T-handle and not over-torquing the thing will usually get the tap to back out. A bit of heat on the part, a bit of lube, a bit of patience. If the steel fingers twist off, you'll have to get them out and then try again. If the tap is a three-flute model, there are three-fingered removers to match. These can be shop-made as well.
All the best on that.
Jim Fair
Dave C07/12/2010 11:24:49
102 forum posts
37 photos
Re your extremely generous offer Johan. Many thanks indeed for your more than generous offer off help removing the tap. I have after a combination of efforts now finally removed the tap though not as cleanly as I would have liked. There was very little clearance around and below the tap to work with and so I may end up making a new part after all. I now wish I'd have logged on again sooner as I would have gladly accepted your offer of help.
I think this one will be put down to experience however I now know what to to in the future,
Many thanks to all for advice and assistance.
Dave

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