Broken tap.

[bob hertrich]

While drilling my Davis lock, which I had a hard time drilling the tap hole in. Appeared to be some what hard steel. The 8-32 tap broke off in the bolster. The other one in the front of the lock went thru OK. I was using tap free on both holes. No way can I get a vise grip to grab the broken tap.What is a man supposed to do?

[L. Akers]

1.  Tap extractor

2.  Use a small punch and tap counter-clockwise on the sides of the broken flutes.

3.  Use a small, oxygen-rich oxy-acetelene flame and burn it out.

4.  Drive it out from the opposite side.

[Scota4570]

I use tiny diamond dental burrs to slice them up.  Your dentist may have some old ones, or ones he does not want.  You may have to buy some.  Anyway, go slow and work the length of the flutes.  This the cleanest way I have found. 

I have been told about heating the tap with an oxy aceteleyne torch then cutting off the gas.  Supposidly the tap will  boil and disintigrate.  Never tried it. 

You can patiently tap the plate with a little hammer.  With luck the tap will loosen or break up.   

I have never had any luck with tiny tap extractors.  It broke because it bound up.  The bind was tight enough to break the tap.  Three little fingers probably won't budge it. 

Know anyone with a flow jet?

If you make a mess of it you can silver solder a bushing in it and re-drill and tap. 

[Kingsburyarms]

I have done the following:

1) If it is a through hole, I have either slotted the tap and used a small screwdriver to "unscrew" if from the other side or drilled the tap and drove it through the material.
2) Used a diamond bit and cut away the tap little bits at a time (see above)
3) Tap Extractor after heating the surrounding metal
4) Made a mess of the lock plate while removing the broken tap, and used a Helicoil (8/32) to repair the threads. I have used Helicoils for many years on everything from engine blocks to Aluminum stripped threads.

http://www.stanleyengineeredfastening.com/brands/heli-coil/screw-thread-inserts

[conquerordie]

I just spent two days removing a broken tap from a tumbler from a TRS kit. No chance of getting another one, so I had to get it out. Extractors never work for me, I tried a carbide burr. Which was somewhat helpful. In the end I heated the tumbler and broken tap as hot as I could, let it cool slowly taking the temper out of the tap, and then drilling it out with a carbide drill bit. Now my hole in the tumbler is too big and I'll have to weld it up, but it'll work.
Greg

[Scota4570]

I was assuming a high speed tap.  The ability to soften carbon steel taps is a strong reason to use them.

[Howard]

What you probably did was you used a dull drill & work hardened the area you tapped. If you can't get it out see if there is a machine shop in your area that has a EDM machine & can burn it out. Good luck.  Or cut the area out & weld it up & start over again.

[Frank]

Never use high speed steel (HSS) taps. Always use carbon steel. They are much easier to remove if broken. Can just use a flat punch and drive out the broken tap. The teeth will just break off.

[davec2]

In the aerospace business I have had to deal with broken taps in almost every conceivable material.  I have tried every permutation and combination of broken tap removal methods.  I would venture to guess they worked less than 10% of the time.  The other 90% of the time, the part that I was trying to save was either severely compromised or completely worthless after the tap was out (IF the tap ever came out).  If your time is worth nothing to you, then you can try all the various ways suggested to get a broken tap out.  You might get lucky.....probably not though.  If, however, you want to not waste your time, remove the tap, and save the part with 100% certainty, do what Howard suggested and take it (or send it) to a shop that can do EDM and go work on something else while the tap is removed.

[pushboater]

I've had luck taking a small driver bit and grinding or shaping a couple of small prongs on the end Spaced to fit down into the spaces between the flutes and backing them out with a small wrench. Done several that way.

[Bill Raby]

   I agree that it was likely a dull drill bit that work hardened edge of the hole. I always replace drill bits at the start of every project for metal work. The small ones anyway. Dull drill biy\ts are nothing but trouble. For tapping use plenty of lube. Work it in 1/8 to 1/4 turn then back it out a half turn. If it is not going through nice and easy, remove the tap and anneal the metal. Harden again when done. Not much help getting it out now, but maybe prevent another broken tap in the future.

[FALout]

Take a small punch, try to push it out from opposite where you were going in with tap.  You could get lucky and it will break into pieces.  You will likely have to go up a size on your screw from 8-32 to 10-32 which is no big deal since they are available.

[thecapgunkid]

A very good, albeit scary post.  Tough and manly as I am ( Semper Fi, do or die, Ooh Rah, Oohrah)  I am sure I would cry like a woman i n labor, a man with a kidney stone or some such  if it happened to me with my limited skills.

Ssssooo, why not buy another lock plate?

Thanks, and,

Don't shoot yore eye out, kid

The Capgun Kid

[tiswell]

Bob Hertrich,
     If you get to the point where you are convinced that you can't get it out with out messing it up, send it to me with return postage and I will get it out and send it back to you. I will use a milling machine with small carbide endmill and take out the center of the tap and pick the flutes out. PM me for my address.

                                                                                                                                                                    Blessings, Bill

[flehto]

I have to ask the question....how are taps broken?. There's  possibly 4 answers....not backing the tap  out to break chips or not often enough, trying to straighten an angled tapped hole by tilting the tap, not enough lube or the right kind and lastly, hitting a hard spot in the steel....which can be caused by a flaw in the steel or w/ certain types of steel, hardening the steel  from the heat generated by a dull drill.  Of course this latter cause would require enough carbon in the  steel.

I'm still using 2 flute or spiral fluted HSS taps from when I was last in the toolroom 57 yrs ago and due to the "soft" steel of gun parts, they're still sharp and have never broken one off.

I do most of the tapping in the drill press by aligning the hole w/ the tap, turning the spindle on then shutting off and while the spindle is coasting, bring it down into the hole and partially tap the hole....the tap stops cutting after a few threads have been cut.  The tap is unchucked and the tapping is completed  w/ the workpiece clamped in a bench vise. This assures that the tapped hole is perpendicular.

If my drillpress had a " spindle reverse", that would be exactly what I used when  tapping holes under power in the toolroom ......Fred 

[L. Akers]

I have to ask the question....how are taps broken?.

I think you missed the most common way taps are broken, Fred.  Most are broken by inadvertent side pressure when tapping by hand.  It is next to impossible to hand-tap without exerting side pressure--and it don't take much.  Use lots of tapping fluid,  make sure the tap is SHARP and advance in small steps, backing out after each advance to cut off the chip.

[FlintFan]

Bob Hertrich,
     If you get to the point where you are convinced that you can't get it out with out messing it up, send it to me with return postage and I will get it out and send it back to you. I will use a milling machine with small carbide endmill and take out the center of the tap and pick the flutes out. PM me for my address.

                                                                                                                                                                    Blessings, Bill

+1 for this method.  I have removed dozens of broken taps this way, and feel it is by far the best way to do it even with having full access to wire and sinker EDM's. 

[TMerkley]

Another option that is used in tool and die shops is to weld a bead to the top of the tap or in some cases with engines the broken bolt.  after some spot welds and building up the surface, you can get a bite on it with another tool, vice grips or something else.  Options....

[ron w]

there are special tap handles that can be had tha have a spindle on the top of the body of the tap to be chucked in a drill press. with this type of handle, you start the tap with a little down pressure from the quill and once the threads are started, it's just a matter of working the tap forward and reverse by hand, advancing it just a bit each cycle. using the drill press's quill keeps the alignment and the return spring in the quill helps to avoid jammed taps on the reverse rotation, which is a very common source of breakage. as said side forces are the biggest reason taps break and it is that side force on the reverse, or clearing rotation that causes the most problems when a little side pressure jams the tap against a chip or two that has just broken off from cutting a thread.

[John Archer]

A spring loaded tap follower works great...it can be used in a drill press or a lathe and they're cheap.

John

[P.W.Berkuta]

While drilling my Davis lock, which I had a hard time drilling the tap hole in. Appeared to be some what hard steel. The 8-32 tap broke off in the bolster. The other one in the front of the lock went thru OK. I was using tap free on both holes. No way can I get a vise grip to grab the broken tap.What is a man supposed to do?

I am assuming that you drilled a through hole in the bolster then went and started to tap the hole and the tap broke. If this is correct then you should be able to get the broken tap out with a punch by breaking up the tap. Start by hitting the tap on the lead end (point-front) with a flat punch to start fracturing up the tap then go to the broken side of the tap and hit it some more with a small center punch. Do this until you get pieces of the tap that you can pick out with tweezers and awl.  It will come out. Next time - use sharp drill bits, don't run them too fast and use oil, drill the hole straight by using a drill press, start the tap straight by using the drill press - tapping with the drill press is also a good idea, use tapping fluid not just regular oil, back up the tap often to clear chips. Hope this helps 

[bob hertrich]

The broken tap is out. I tried a couple of the methods suggested with no luck. A friend who I had worked with brought it to his companys machine shop. Thanks for all the reply's. There is a lot of good info in them on how to not get myself in trouble again.

[Goo]

After the fact comment here. If you have access to a small kiln what would be so bad about annealing the entire part?  This would force you to heat treat later but... Maybe you won't lose the whole thing and the broken bit would be able to be removed more easily.     As a subtle message to the lock manufacturing industry I personally won't mind paying a couple of extra bucks for a lock that is evenly annealed or tempered I can work with no surprises and not snap off small taps which cost me time , aggravation  and lost tools .