26 replies to this topic

[SGropp]

Breaking a tap off in a piece of work can be a frustrating and potentially expensive mistake.

I see all kinds of little gadgets for sale made for removing broken taps, but have never tried them.

The best technique I've found for removing a broken off tap in a hole is to burn it out with a plasma torch. This works particularly well in blind holes.

With a center punch or pin punch break off any jagged ends of the tap that are sticking out of the hole.

Place the tip off the torch straight and centered over the hole and tap. When everything is lined up ,clear your mind of negative thoughts and hit the trigger of the torch for a momentary burst.

[ Do not even consider doing this without at least a pair of shade 5 or darker safety glasses and a pair of gloves ]

Blow out the hole with a blast of compressed air and repeat. Use a narrow pick probe to pull out any chips . Blow the hole clear again and give it another blast from the torch if needed.

When the hole feels clear, and things have cooled down, carefully run the tap drill down the center of the hole, blow it clear and finish tapping the hole with a good quality sharp tap and abundant tapping fluid. The existing threads should still be intact and undamaged.

I've never had this technique fail me on taps up to about 3/8".

The plasma machine should have sufficient power to do the job and the torch should be fitted with a drag tip in good condition.

[forgemaster]

To avoid wrecking a good centre punch digging the tap out, I will use a concrete nail, the sort that they fire into the concrete with an explosive charge (ramset is a name that springs to mind).

Phil

[Phil Krankowski]

Got advice for someone without plasma?

I really do hope I will never need this advise.

I cringe at the thought of a broken tap that I cannot grab one end or the other and twist out with vise grips. Yes, this will work IF there is enough projection, 2-3 threads on 1/4-20. Been there, done that. Don't grip too hard and break what is left. Consider filing the front of the jaw clean/square to get a closer grip if the jaw is worn

For taps that are large enough to get a wire into the chip groves, you can use a pin spanner after getting as much chip out of the way as possible. No I have never had the displeasure of trying this.

Phil

[HWooldridge]

Dry ice and acetone followed by a sharp rap with hammer and punch works reasonably well on small pieces or taps where you can dip the work in the solution (use suitable PPE to protect your body). Liquid nitrogen is better but you can get CO2 and acetone in most areas with grocery and hardware stores - cheaper, too. IIRC, this mixture yields about -100F or so and will chill a tap to the point where it can usually be broken.

The other thing I've done is to heat the tap to bright orange and quench in water (if the workpiece size and composition will allow it) - rap the tap and she usually busts up enough to remove.

[BIGGUNDOCTOR]

I use solid carbide spade drills to get mine out. Spot it with a large one than drill it with one that drills out just the web. Collapse the teeth, and it's done. This is the best way I have found when a mill, or lathe can be used. Amazing how well a carbide drill cuts through a quality HSS tap.

On cast iron parts (exhaust manifolds) I have blown them out with an O/A cutting torch.

Someday I would like to pick up a tap disintegrator. The portable units have a lot of uses besides tap removal.

[Bob S]

SGropp, on 10 March 2010 - 03:49 PM, said:

When everything is lined up ,clear your mind of negative thoughts and hit the trigger

Good advice for a variety of situations.

Most tap drill charts call for 75% full thread. Unless that much thread is really needed use the next larger size drill to minimize tap breakage which can ruin your day.

Don't forget to duck when you pull the trigger into a blind hole.

Bob

[Dragons lair]

Got a 1/4 20 tap tap broke off. A 1X.125 fb with a 1/4 hole Weld the FB to the bolt/tap Tap with a small hammer
Ken

[SGropp]

The wide variety of techniques offered indicates that this happens to the best of us.

The big advantage of the plasma torch solution is that it works on a large assembled pieces that cannot be brought to bear under a mill or drill press.

I'm not sure why the plasma arc vaporizes the material of the tap and leaves the threads in the parent metal intact, but that is what happens virtually every time in my experiance.

Sometimes there is the option of drilling and tapping another hole close by, but usually the hole has to be on the exact same layout.

[John B]

SGropp, on 11 March 2010 - 12:28 AM, said:

Sometimes there is the option of drilling and tapping another hole close by, but usually the hole has to be on the exact same layout.

If that is the case if all else fails, you ccould use a tank cutter, or hole cutter or even a gas cutter to remove the damaged hole, chamfer the new hole well, and weld in a solid plug, dress off, redrill and tap .

[Dave Hammer]

There are tools designed specifically to extract broken taps. This site has one example:

http://www.waltontoo...ts/extractr.htm

Seems to me... using the proper tool would be much safer.

[John B]

Dave Hammer, on 11 March 2010 - 04:27 PM, said:

There are tools designed specifically to extract broken taps. This site has one example:

http://www.waltontoo...ts/extractr.htm

Seems to me... using the proper tool would be much safer.

I agree, but they don't always work.

[Dragons lair]

Got 2 of them in the tool box. Both have bent or broken fingers.(yard sale find)
Ken

[Steeler]

Dave Hammer, on 11 March 2010 - 04:27 PM, said:

There are tools designed specifically to extract broken taps. This site has one example:

http://www.waltontoo...ts/extractr.htm

Seems to me... using the proper tool would be much safer.

Thanks Dave. I didn't know that such a thing existed. I've been able to remove them so far by fiddling, picking and proding for long periods of time. I think with careful use of a broken tap extractor, a lot of lost time and frustration can be avoided.
It's a good day when I learn something new. Steeler.

[BIGGUNDOCTOR]

I haven't had much luck with those extractors, and I sometimes use spiral flute taps which these will not work on. You also need a set of those to fit the various sizes. Most of the taps that I have broken recently have been while driving them with the mill, or lathe, so I just pop in a carbide drill and drill them out. A couple of different size drills will work on a wide variety of different size taps.

[Mainely,Bob]

BGD,Are you using spiral flute carbide drills or straight flute?
Have you ever tried a carbide 2 flute center cutting end mill?I have a couple but don`t want to risk them if they tend to break rather than work.

When working at the plant or the yard if a tap extractor didn`t work we generally just called the EDM guy.

[BIGGUNDOCTOR]

The drills I use are made in house. We use a lot of round carbide where I work, mostly for form drills. I have used a couple of different versions. One is ground to a taper kind of like a pointed cold chisel, and the other has a couple of short flutes. The short fluted one is a little better when getting to the end as it is bearing on more area which makes it less likely to catch.

It does spoil you when you have primo material, and primo equipment to work with. The carbide really makes short work of a tap, and the Ewag grinders that we have make beautiful tools out of it.

As for using an end mill. I would be somewhat hesitant to do so. I may try it next time since we have quite a few carbide endmills too, but most of ours are center cutting 4 flute. I will let you know what I find out. I am expecting it would chatter some, but I could be wrong.

[arftist]

I use center cutting four flute solid carbide endmills to remove taps. I buy them just for that purpose. They are expensive and don't last long, but work very well. I only use 1/4". It is all I ever need. I don't break many big taps, and there are other ways to get large taps out.

[Mainely,Bob]

So the four flute are less prone to breakage.
I`ll keep this in mind as I look thru tooling at the sales.
Thanks for the tip.

[Bentiron1946]

When I was in high school we didn't have plasma cutters, liquid nitrogen or dry ice and our shop teacher being a retire Marine Corps major was not one to make life easy on us had we by chance to break a tap in the process of cutting threads in a blind hole. He had us break up the the broken tap with a center punch, then re-drill the hole and tap to next larger size. Isn't life wonderful now!

[Dragons lair]

Bentiron, We could be bros, Vintage 45 ex marine. Naw it was yrs later finaly had access
to EDM. Last shop I worked for GAVE away a usable edm machine when they closed. Good friend used to make all the carbons for it. Nasty xxxx grinding the electrodes.
Best of luck on the upcoming slice and dice.
Ken.