Shop Managed to get broken tap out

[Larry_C9]

Yesterday was not such a good day. I was just finishing up a small mild steel part for the Corliss engine I have been picking away at and only had two 5-40 holes to tap. They are blind holes no more than 3/16" deep. I got the starting tap down the first hole and was on my way back out when it got quit tight. Probably swarf stuck in the tap. I was working it back and forth to try and free it up when a small piece of the tap broke off in the threaded hole. I wasn't very pleased because I usually don't have much success getting pieces of broken tap out, even on larger taps than this. I had visions of having to make the part all over again, which would probably take few days at the speed I work. So made the right decision to just leave it for another day.
In the mean time I did some searching on-line and found a video from a fellow who was successful removing a small broken tap although he did quit a bit of damage to the threads. He used a very small pointed diamond coated burr in a Dremel tool.
So today I thought I would give it go because there was really nothing to loose. Luckily it was a 2 fluted tap so I was able to work back and forth across the center being very careful not to touch the treads. I managed to grind a slot down into it aways so I thought I would try a very small slotted screwdriver and see if it would catch the piece of tap. It seemed to be catching so a put a pair of pliers on the screwdriver to increase the torque I could apply. I was amazed when it started to turn and in a few turns it was out. I blew out the hole and ran a bottom tap down the clean it up. On inspection of the hole the threads appear to be undamaged. Today was a very good day.

 

[PeterT]

That is a good day. Often it doesn't end as well with broken taps.

 

[SparWeb]

Buy a lottery ticket today because that's good luck you had, there.

 

[Everett]

That is definitely good news, especially with a hole that small. I've had a couple bad days where a Dremel and small diamond burr eventually got me out of the fire.

 

[Susquatch]

Another handy tool to have is a Walton Tap Extractor. It has flattened spring steel pins that go down inside the tap flutes and a sliding holder to stop them from twisting.

They don't always work, but my success ratio is around 2 out of 3.

Yes, I break a lot of taps. It isn't always easy to get good alignment working on farm equipment.

Another trick I recently came up with when I know the risk is high, is to post drill a lower thread fit % for the first diameter of length and a longer thread engagement to compensate. The lower thread fit allows the tap to self align a bit better. I haven't broken a tap yet since I started doing this.

 

[Chip Maker]

When all else fails, I've drilled taps out using carbide.

 

[Susquatch]

When all else fails, I've drilled taps out using carbide.

I would not have thought to try this. Diamond yes, carbide no. I'll give it a whirl "next time".

 

[Chip Maker]

I would not have thought to try this. Diamond yes, carbide no. I'll give it a whirl "next time".

Believe it or not, but we used cement drills (Greenlee) sharpened on a diamond wheel.

 

[Larry_C9]

I rarely break a tap because I use a home made pointed center in the tail stock when on the lathe or in the chuck above the tap on the mill . This keeps the tap perfectly inline and also absorbs any side thrust from the rotation of the tap holder. This one caught me because the hole was tapped and I was on the way back out.

 

[CWret]

is to post drill a lower thread fit % for the first diameter of length and a longer thread engagement to compensate.

Please expand upon this explanation/description of your new tapping procedure.
Tks
CW

 

[combustable herbage]

If you wouldn't mind I would like to see a picture of your setup, breaking taps can be a challenge for me.

 

[historicalarms]

Please expand upon this explanation/description of your new tapping procedure.
Tks
CW

Basicaly you drill a short distance of "pilot hole" for the tap to start ot bite into and line itself up for the rest of the hole.

 

[Bandit]

I have never had a problem breaking tapes, just putting them back together! They only break on important pieces or in difficult areas to get at, and at the last hole of many done, just when you start to think you did it great.
Yes, drilling a larger start to the hole helps, as does useing a centering/holding devise. A piece of thick metal with a clearance size hole for tape size can help to line up and keep the tap starting straight. checking depth of hole verses length of tap threads, put a piece of tape on the tap to mark depth of hole minus the taper of the drill nose.
And remember, one good turn doesn't always deserve another,,,, snap!

 

[Susquatch]

Please expand upon this explanation/description of your new tapping procedure.
Tks
CW

What @historicalarms said.

But to be clear, I only do this when I'm tapping and drilling freehand. If I'm using my drill press, my mill, or my lathe, it isn't necessary. I confess I've broken the odd tap when I'm using these machines, but it's a rare occurrence and usually caused by cheap taps. On the other hand, getting a square hole and starting a tap squarely in that hole can be next to impossible with a hand drill. Starting a tap on an angle to the hole is a recipe for broken taps.

But doing a shallow oversize hole in an existing hole is pretty easy. Unlike a tap, a slightly oversize drill wants to follow the previous hole if you let it. So I do. This then leaves a guide hole that is nice and aligned with the deeper hole which the tap then wants to follow too.

It is cheating, but it works.

I've also done what @Bandit describes with guide bars but not with much success. I usually can't get them any squarer than the tap!

 

[thestelster]

When I have to tap a hole. I go to my drill/tap app: Tap and Drill Chart Calculator, and depending on the material and thickness I will be tapping, the app suggests what thread percent is required and suggests the appropriate drill bit to use to acheive that thread engagement. The attached files are numbers for 1/4"-20.

Always use a small center into the back of the tap, or tap handle whenever possible. Or power tap.

Choose the appropriate tap, not necessarily tolerance, but style: taper, plug, or bottoming. As well as hand tap, spiral pointed, spiral fluted.

Chamfer the hole before you tap, or even countersink slightly below the surface with the screw/bolt size.

Plenty of cutting oil, half a turn in, full turn out. If its a fairly deep hole, go half way in, completely remove, blow out all swarf, more cutting oil, and continue.

 

[Susquatch]

drill/tap app: Tap and Drill Chart Calculator,

I see you liked the app I bragged about a while back! I love it! Not sure why it didn't get more traction on here. It is a really awesome app that everyone on here should have and use. Unless they have an Apple..... (Insert evil giggle here).

@CWret FWIW - this is the app I use to identify the lead drill with a low % I use to start.

Stell is talking about tapping on a machine and I was describing what I do on farm equipment too big to bring to a machine.