Drilling out a broken thread tap

[tylernt]

Oxy-mapp has a much softer flame that would be unacceptable to burn out a tap. ... only oxy-acetylene will work.

I was under the impression that once the metal was red-hot, you depressed the oxygen lever and the oxygen did the cutting, not the fuel? But I'll admit I'm no expert.

The fuel regulator for acetylene can indeed be used for propane in most cases.

I've seen that mentioned, but I've also seen others say that 15PSI often isn't enough and most acetylene regs don't go higher (or at least, the gauge is in the unmarked "red zone" in the 15-30 range).

 

[Twiggss]

O/A torch is my go to. This week i used it to remove a tap in the crank shaft of a large gen set. Some dingle berry broke a 25mm(ish) tap off while chasing the threads. He didnt have a big enough tap handle so he used a 1/2in impact with a 12pt socket. When he bottomed the tap it broke about 1in shy of the surface. What a *****.

wow... just wow..

 

[rlitman]

I was under the impression that once the metal was red-hot, you depressed the oxygen lever and the oxygen did the cutting, not the fuel? But I'll admit I'm no expert.

You are correct. Cutting is done with the oxygen alone, and in most cases better results can be obtained with oxy-propane (and even oxy-gasoline) than with oxy-acetylene.

But this is an exception. The issue in burning out a tap (at least a smaller one), is that you must heat the tap above the pre-heat temperature without heating the surrounding metal to that temperature. This is much easier to achieve with a sharp flame, and only oxy-acetylene can do this to get you started.
Once you reach the pre-heat temperature, you can turn off the fuel, and just burn away with the oxygen.

 

[GRX]

Since Propane vs Acetylene was brought up, it is worthy to note that the respective flames have very different heat profiles. With Acetylene most of the heat is contained inside the inner cone. With propane there is far less difference between that and the outer flame. Also, Propane burns more cleanly than Acetylene, so use each accordingly.

 

[jjpp]

A carbide burr in a die grinder on low speed works fine for me. You can use a pencil grinder for smaller jobs.
If you are going to use this method just don't try to heat it first or it will be that much harder to grind.