Another Broken Tap

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4GSR

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Well Buba broke off another tap in a thru hole in my shop today. Almost had it tapped all the way thru, too. The tap size is 5-44. It is in a old boring bar that I'm trying to salvage for use. I have one or two carbide drills and end mills small enough that may get the broken tap out. But before I tear up my carbide tooling, I like to see what recommendations are suggested on removing the tap. EDM is totally out of the question. This is a junk baring bar before I started this and will junk it before sending it out to burn out a tap.

Like to hear from others on how they removed small broken taps.

Ken
 
In the past I've used a 1/8" punch and just hammered it out, then drill and tap to a larger size. Try sticking nails or pins in the flutes, then using a vise grip to twist on the pins.
 
If I didn't care about the heat treat on the bar, I'd anneal the tap with a torch and just drill it out. I have taken the butt end of a carbide drill about the size of the minor diameter and ground a 3 or 4 sided pyramid with a sharp point. On something that small, a machine ground point would work better. The tap must be pretty flat where you need to make the hole with this method. Run the spindle speed as high as possible, and a air blast to keep the tiny chips clear. Pecking is in order. This method leaves just the flutes engaged with the internal thread and they can be picked out. I've only done it a few times on taps that small, but it will work.

Chemically, there is a product called Tap Out, kind of hard to find, which is a blend of acids. Seems to prefer high carbon steels like taps. Best for use on nonferrous parent materials, but if you keep an eye on it, you can use it on a carbon or alloy steel.
 
Can you TIG weld something to it so you can turn it out? Maybe just stick the TIG tungsten to it.
 
You can buy a 1/8 inch diamond drill. They have those diamond coated hollow core ones I've seen on my favorite auction channel. Heating and annealing sounds like an idea. I have never tried that. Mainly I end up making the part over. Last time I busted a drill, I drilled out from the other side and knocked the broken drill out with a punch. Then I bored a large hole and plugged the piece if that can be an option for you.
 
Cut your losses, toss it in the scrap bin. You'll have more time in it than what it's worth, and it still won't be 100%. Besides that, you need something for your Christmas list.;)
 
Tony Wells said:
If I didn't care about the heat treat on the bar, I'd anneal the tap with a torch and just drill it out. I have taken the butt end of a carbide drill about the size of the minor diameter and ground a 3 or 4 sided pyramid with a sharp point. On something that small, a machine ground point would work better. The tap must be pretty flat where you need to make the hole with this method. Run the spindle speed as high as possible, and a air blast to keep the tiny chips clear. Pecking is in order. This method leaves just the flutes engaged with the internal thread and they can be picked out. I've only done it a few times on taps that small, but it will work.
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We used this method many many times to get broken taps out of parts when I was a moldmaker. It does work but will take some time to do. Somewhere on the internet there were plans for a home made EDM for burning taps out. If I can find it again I will post it.
 
I built a simple edm powered by my old welding transformer. Heaps of plans online, mine is a WH&S nightmare so I wont post it.
Burnt out taps from aluminium and steel with no problems. Well worth building so it handy for the future.
The simple versions really are simple and still work.
Can also use carbon electrodes and burn fancy shapes such as square, triangular etc not this I have yet.
 
Hey guys, thanks for the thoughts you have given.

I think I will try the carbide drills and diamond burrs first. If no luck, I'll try heat to anneal the tap. Not too worried about the HT in the bar material. Not like this bar will ever do production work ever again.

A BIG plus on a tap burner, EDM machine. Dad had one that was pulled out of a junk pile at a machinery dealer many years ago. We managed to rebuild it a bit and get it to work ok. I did burn out lots of taps with it over the years. Wish I still had it.
 
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