sligermachine

BROKEN TAP removal

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My favorite way to remove a broken tap .just tap it with a center punch back and forth just try to move it .002 each way back and forth blow lots of air between tapping it .Back it out put the punch at the highest angle you can possibly get it to go . Use 2 punches as a key to unscrew the tap bend the ends of the punches so you can push around the corner . Next time I brake a tap I will take more pictures  the taped hole in uses after I removed the rest of the tap 3/8-16 tpi.--- 5a8d13e21f26b_20180220_140931_Burst011.thumb.jpg.eeef63452dc380b2360d36431f71c771.jpg kyle 

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       Even if it brakes off below the surface I use the same method  with slightly bent punches so I can use them below the surface .

 

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Braking a tap is one of those things that just makes me cringe knowing what I’ll have to go through to get it out. I use the same technique as you both and sometimes use a small diameter dremel cutoff wheel and make a slot in the end of the broken tap for a screwdriver. Tap it a few times with the punch to free it up then try the screwdriver. I’ve had it save me a lot of time “sometimes” but not every time of course. The slotting technique works great on bolts that get sheared off.  

 

One of the best “tricks of the trade” ever shown me was I was a young man that I’ve never forgotten was how to remove an inside bearing race that you couldn’t get underneath to pry out. One day while at my job, I was trying to do just that, an old timer walked by and asked me if I wanted him to show me how to get it out. Of course I agreed so he told me to carry it over to the welder and run a nice bead right around the whole face of the race. My thought was he was going to have me weld on a piece of scrap to help pull it out. After I ran the bead, he asked me to give him the gear box cover (it was about 12”square) . He put on his glasses and while holding the cover in his two hands got a closer look at my bead and signed in approval, then rotated the cover in his hands and gave it a good shake. That damn race fell right out ringing on the floor as it hit the concrete. I’ve never forgotten that lesson and have used the technique hundreds of times now. Of course I understand how the weld shrinks the race but never thought to do it that way. A lesson well learned!

Edited by chistech
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Years ago a good friend broke a tap off in an expensive, very-hard-to-find exhaust manifold from his muscle car. He tried everything to get it out, to no avail. Then another buddy of  mine (Dave) heard about his problem, and offered to fix it for him. Dave took the manifold to the machine shop where he worked, and set it up in an "EDM machine," which stands for Electrical Discharge Machining. The way it works, as I understood it, is that the machinist cuts a carbon electrode to the shape he wants the hole to be, and then "burns" a hole of that shape into the work piece. For the removal of this stubborn tap, he used a carbon electrode in the shape of an Allen Key. He burned that hole, and then simply inserted the Allen wrench in the new hole, and spun the broken tap right out. He explained to me that the new hole in the middle of that broken tap (or a broken, rusted stud, etc) relieves the pressure on the threads on the outside of the tap (or stud, broken bolt, etc). Then Dave went ahead and removed the rest of the broken-off studs in that manifold, which the other guy had been trying to remove in the first place. I thought that was really cool, and SO much better than the crude methods I would have tried. 

 

If you don't have a friend like "Dave" at a machine shop, I'm sure the process would cost you a substantial fee (couple hundred bucks, maybe?) But if I had a rare and valuable part with a broken stud or tap in it like my buddy did, I would gladly pay it.

 

Full disclosure: I am OBVIOUSLY not skilled in machine work at all. I'm sure most of you already knew all about the EDM machine, and what it can do. But I did not, prior to that incident, and I found it fascinating. I thought a few other readers here might enjoy it too. Cheers! 

 

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The hex electrode is a bit extreme. Far simpler is to just use a tube shaped electrode. Cuts the core out of the tap and the pieces fall out. Less metal being cut makes it faster too. We had a "tap burning" machine at where I used to work. Just a crude EDM that used a tube as an electrode to burn out the tap core. I also saw a home made tap burner powered by a car battery. The tube electrode was held by the armature of a solenoid.  When the electrode touched the tap it completed the circuit and the solenoid pulled the tube and broke contact. Kind of a door bell effect. The arcing at the tube/tap burned the tap core away. Main problem with the EDM technique is it must be done under a liquid to flush away the particles...............Bob

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Bhig, 

 

Would the tube electrode also work on rusted, broken studs or bolts, with solid threads? Maybe that's why Dave used the hex electrode? I don't know myself. Just asking out of curiosity. 

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An EDM machine will cut any metal. Hardness matters little. The electrode can be most any shape and it will cut that shape. With the proper sized/shaped electrode the entire tap or stud, except the actual threads, could be eroded away. There are some limitations because generally the electrode also wears so a blind hole tends to be tapered towards the bottom. It's also not a fast operation although typically it's a set and do something else for awhile type of deal.

Also there's the problem of the part having to fit on the machine and not mind being submerged in de-ionized water...................Bob

 

 

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This piqued my curiosity so I googled around broken tap EDM. Seems there are any number of portable tap remover  machines available starting about $1500. Still need a water flush but can use tap water if need be................Bob

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I have used EDM on some of my projects.  On one I needed a square hole in a metal piece about 4 inches long and in production it would have been broached.  Used EDM and it came out perfect and also put a grease passage in the part.  It works very well and in the big picture is not that expensive. IMO

Edited by Larry Schramm (see edit history)
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Larry likely utilized a wire EDM. Instead of a shaped electrode that is plunged into the work piece a wire EDM uses a spooled wire to cut a shape or make a cut out. Again the piece's hardness matters little. Typically the shape or cutout desired is computer controlled and can be accurate in the extreme...............Bob

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On 2/23/2018 at 11:19 AM, Bhigdog said:

An EDM machine will cut any metal. Hardness matters little.

I have used the punch method  100 to 200   times a year most the time it takes 2 to 5 min to get out a tap. But like anything my punch drawer is full of bent punches from doing it this way . My EDM  is a punch sharp hit it hard blow lots of air the tap brakes off like glass in little bits . most of the time it does not hurt the original threads sharp punch hit sharpen punch hit every hit normally makes punch flat on end . only hit with a sharp punch right over edge of thread . I have never took pictures of the process never thought much of it with in  a stone throw of my shop door is 8 big diesel  repair shops do it for them all the time. 

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Thanks for posting this tip, Sligermachine. I'm sure it will be helpful for anyone who finds themselves in a pickle like this. I will certainly try it, whenever it happens to me again. But I am perhaps over-cautious whenever I am running a tap, cutting only a very short amount before backing it off and adding oil, etc. Then cautiously proceeding again. Still, breaking one off in a hole is inevitable, I suppose. So I will put your advice in my bag of tricks for future needs. 

 

Cheers! 

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On 2/23/2018 at 6:39 AM, chistech said:

“tricks of the trade” ever shown me was

Use it back words  put cup races in the freezer  use a heat gun on the hub of the car truck and they  would drop right in with a push of your fingers . I try not to hit a race in at all with a hammer  

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22 hours ago, lump said:

cutting only a very short amount before backing it off and adding oil, etc.

 

Good advice. Also don't use cheap taps and understand they do get dull. Testing it's cutting ability by seeing if it breaks or not is poor practice. The correct tapping oil or compound is also important. The best and least expensive lubricant for tapping steel that I've used is bacon grease. Don't laugh or scoff until you've tried it.................Bob

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15 hours ago, Bhigdog said:

correct tapping oil or compound is also important. The best and least expensive lubricant for tapping steel that I've used is bacon grease. Don't laugh or scoff until you've tried it...

    I don't push any one kind of tools but this cutting oil .If I run out of it I will not tap a single thing with out it . with it a tap lets say 3/8-16 TPI  can tap 250 holes 1.5 deep  and leave good threads  in 304 stainless steel . with out it 12 holes  and dig a broken tap out . But hay when I buy Taps I just buy the best USA stuff . now next time my wife makes some bacon .I will let you know how that goes to --kyle

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Edited by sligermachine (see edit history)

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Now I’ve got to tap some stuff for the hell of it. I love bacon and now I have an excuse to cook some up!

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