Removing broken taps?

[Arnak]

Hi Folks,

Can I have some suggestions on removing broken taps please?

I saw on another post that annealing was one way to go about it, could you expand on that method please?

Arnak

[lancelot]

Hi Arnak,
the ''annealing'' approach really depends on the material that the tap is broken in also the hardness or quality of the tap, consider a hypothetical situation...the last lap of a set of tapped holes in a fully machined loco cylinder... cast iron...the ''ALUM'' system wont work as it only works on ''non ferrus'' if you attempt to heat the cylinder to ''anneal'' the tap the possibility of distortion of the cylinder exists, so I would suggest if the tap is big enough to use a ''TAP EXTRACTOR KIT'' then go that way, if of the smaller sizes as 2ba or smaller, I would try drilling with ''COBALT...or...DIAMOND'' drills...If the tap is broken in ''NON FERRUS'' ie... Brass or Gun metal, I would suggest the ''ALUM'' method of chemical removal as described in the forum archives, it may be slow, but it certainly works.
All the best for now,
John.

[Arnak]

Hi Lancelot,

Thanks for the reply.

My usual problem is of course the smaller BA sizes, usually in steel.

I read somewhere in a older post regarding making a spark erosion machine but I can't find the thread. 8-((

I'll look up the Alum method and see what that entails.

Thanks,

Arnak

[districtgrandmaste]

Provided the tap is in Brass or Gunmetal I can recommend 'The Alum Method' described in another thread.

I had this problem and Alum was brilliant and effortless!

[ron]

This has limited potential, I've managed to drill out a hardened tap using a solid carbide slot drill in the milling machine, the slot drill was toast when I finished and I had to tap the hole larger than originally specified but it did solve the problem.
Ron

[Prowe]

Or alternatively you can be lazy like me and employ your local friendly(?) small engineering shop to spark erode it for you. Was quite pricey around £35, but saved hours of work machining a new casting as I could see no other way around the problem.
However if I had been a member or even known of this forum at the time, I'm sure that I would have tried the alum method.

Hindsight is a wonderful thing.

Regards,

Phil

[stevep]

I have successfully removed broken taps from non-ferrous materials by leaving the job in the acid bolier pickle. After a while, the crests of the threads on the tap are eroded, and the tap can be knocked out.

Steve