possible to regrind tip of broken tap??

[crueby]

Just broke a small tap (4-40) off near the tip, with quite a bit of the full-thread portion remaining. Was wondering - is it possible/advisable to regrind the taper portion of the tap an keep using it? Or will it be more trouble than its worth? Dont break one that often, but if they are salvagable that could save a few bucks.
Someone out there must have tried this - any experience good/bad/horror-story to share? I assume it would have to be done with lots of cooling to avoid messing up the hardness.

 

[Tin Falcon]

is it possible/advisable to regrind the taper portion of the tap an keep using it? Or will it be more trouble than its worth? Dont break one that often, but if they are salvageable that could save a few bucks

first of all there are many styles of tap. sounds like you are referring to a four flute tapered or plug hand tap.

my suggestion is grind the end square and use it as a bottoming tap. I worked in a shop where the purchaser only bought plug taps so if we needed a bottoming tap find a broken one and off to the grinder.

I much prefer spiral point or spiral flute taps as they are stronger and can be used under power and are less likely to break.
Tin

 

[portlandron]

Second the grinding the tip flat and using it as a bottom tap.
If you were to try and grind a tapered start on the end and did not have each flute ground the same it would be very hard to keep the tap straight
(90 degrees to the surface of the material being taped).

 

[napoleonb]

Seconding the bottom tap grind.
I don't know why the tap broke in the first place but i used to "backgrind" the shaft on some of my taps. When the tap breaks it breaks at the weakest point (the grinded shaft) and would be easy to extract from the workpiece.

This trick isn't necessary for all taps but only if you're working on a rahter expensive product with dodgy setups or extended taps.

 

[gus]

I support regrinding as per Tin Falcon's and others. Broke a 1/4'" BSF tap during my Trade School days. Quietly reground and send back to tool store. Seen my uncles doing it in 1960.Mate of mine drew out same tap and found it to be sharper than all other taps he used for project work.

 

[don-tucker]

I have always done it ,grind it square then put a bit of rake on the sides,not as good as the original but works.
Don

 

[rklopp]

I'm going to be a contrarian and say forget it, it's not worth the time or future ruined part due to a busted tap. Save the piece of tool steel for a small boring bar or something, and buy a new tap.

 

[crueby]

Thanks for all the advice - I like the idea of using it as a bottom tap.

 

[Gedeon Spilett]

I do have many bottoming tap, even if one is enough !