Snapped 4BA Tap

[Peter BellParticipant @peterbell11509]

 

I have been clumsy enough  to snap a 4ba tap in a bit of 10mm x 25mm steel.

The remains are well rooted and almost flush with the bar. 

 

I know this is an ancient problem but does anyone have a good method of getting it out without resorting to a spark eroder etc (which I dont have!) ? I could plug the bar and redrill and retap 4ba if necessary afterwards.

 

 

Thanks  Peter

[Peter BellParticipant @peterbell11509]

[JasonBModerator @jasonb]

A couple of small metal pins down the flutes of the tap and a tommy bar between and you hay be able to wind it out, just like a tap extractor. Can take several attempts and a bit of picking with an old scriber.

 

Jason

[Peter BellParticipant @peterbell11509]

Thanks Jason. Just tried that but not a enough room to get pins of any size in,  it is snapped on the taper part and is really tight.

 

Peter

[KWILParticipant @kwil]

You say plug the bar?  Are you able to drill in from the other side, directly opposite the original hole?  If so you may be able to punch out the offending tap and then as you ask, plug and retap from the starting side. What is the component?

[Michael Cox 1Participant @michaelcox1]

Is it a carbon steel tap or an HSS tap? If it is carbon steel the just heat the part to red heat and allow it to cool slowly. The tap will then be soft and it can be drilled out using a normal HSS twist drill. Then the hole can be plugged and retapped.

Mike

[John OlsenParticipant @johnolsen79199]

Do you have an air die grinder or a Dremel tool? With a tiny diamond burr you can grind away enough of the tap to get the remains out, usually not wrecking the hole too badly either. It does tend to use up the burr, but they are not too pricy.

 

regards

John

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Just make a hollow drill out of silver steel and drill around the outside – this procedure works down to microscopic sizes and leaves a clean hole for the repair plug .

[Richard ParsonsParticipant @richardparsons61721]

 

One of the many reasons why taps break is due to them getting jammed up with swarf. I was taught 1/3 turn forward and 2/3 turn back to cleat it. It looks as if this is what you have got. Have a look at the broken bit of the tap. Does it show a twisted fracture?  Try a little ferric chloride solution this may well eat away the harder tap and the fine swaf. It takes a few days but it works. There was l long discussion about this in an earlier thread including how to do it.

  Good luck!

[MikeParticipant @mike89748]

Not sure I remember this correctly, but I seem to recall a toolroom engineer once telling me that in his shop they caused snapped-off taps to shatter by using an ultrasonic probe. Is this right – does anyone have any details?

[Peter BellParticipant @peterbell11509]

 

I thought it must have been covered a few times but could not find anything. Unfortunatly it is the taper part of the tap that is broken in and I knocked it when returning rather than snapping it while tapping. It is also in the full depth of the plate but broken flush.

 

Tried a dremel but only succeeded in ruining the diamond burrs so I think it is HSS.

 

Unfortunatly I do not have any ferric chloride but I like the idea of making a “hollow” drill to take the lot out and plug it.

 

Anyone recommend a tooth shape fort he hollow drill?

 

Thanks  for all the suggestions

 

Peter

[mickParticipant @mick65121]

not that its a lot of good if you don’t have any, but three square stellite run at speed will take out HSS taps.   

[Richard ParsonsParticipant @richardparsons61721]

You can get Ferric Chloride from any one who sells electronic bits.  It is used for etching PCbs. Have a squint at Farnells or RS – usual disclaimer.

[Michael Cox 1Participant @michaelcox1]

Ferric chloride will attack the steel as well as the tap.

Mike

[TomkParticipant @tomk39956]

Mick

           Don’t know if you have used 3 side stellite drills but they are not for faint hearted.

I have some from my days in working in a toolroom where we used them to modifiy tooling that had been case hardend. The process is what I would say brutal, I have used them up to1/2″ dia. You have to run the drill at high speed 1000 rpm plus and have the job bolted down, then apply a great deal of pressure and  keep it there until the work and the drill starts to glow red hot then the drill starst to cut through the steel like  it is as soft butter. It is a local anealing process. I have used them to drill holes in HSS hacksaw blades. Also tried them on broken taps but not had much suscess.

[Steve WithnellParticipant @stevewithnell34426]

Unless there is a lot  of work in the “piece of steel”  toss it and start again.  You can mess about for ever trying to get broken taps out.  A tap in steel is particularly hard to resolve.

 

Unless of course you want to become expert at removing broken taps

 

 

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

The traditional method of removing broken taps in a toolroom is to turn a rod 
from soft material such as aluminium to core size of tap , make a little well of
plasticene around  tap position , fill it with coarse grinding paste then set up the rod

in a drilling machine and use it and the grinding paste to grind through the tap .

 

Works in minutes if you do it right and and hole is usually undamaged .

Spark erosion is the cleanest and fastest method by far but the equipment is
not readily available even in industry .

 

On the ultrasound question I have heard of this but what actually happens is

a combination of two things – the tap gets heated and if carbon steel it may be

enough to soften the metal and the multiple impacts would tend to loosen the tap in the hole . This is one of those many quirky things read about once somewhere and then quickly forgotten because its useless in practice .

[Author]

Posts