2 secs to break 2 hours to remove

just broke a 7ba tap in a 3/16'' piece of stainless steel tried knocking it round nope dried knocking it thru nope in the end i heated it to bright cheery red and broke it out with a carbide scriber then drilled the rest out, result nackerd tap nackerd scriber but saved work piece,

so my question is would the heating of it to such a heat

a) changed the structure of the tap and made it more brittle as before the heat it wouldnt break up.

b) i was just really paitant and as the scriber was harder then most things that would fit in to the hole it finally gave in

don't laugh to much my pride is failing me

Edited By michael burton 1 on 20/02/2012 01:55:47

Edited By michael burton 1 on 20/02/2012 01:57:44

Edited By michael burton 1 on 20/02/2012 01:57:53

Hi michael

Was it your Tich you were working on. tapping 7BA in stainless can be tricky, use lots of cutting oil, a starter or first taper tap, slowly turn in a tap, about 1/8th of a turn then reverse this helps clear swarf, in stainless you should hear a slight click, continue doing same untill through. If you just try and turn tap all the way through without doing this will lead to dissaster. then use next tap. Heating will help expand the work but will alter the structure of the metal and will need to be retempered. you do not say what the component is, how complicated or if it could be just scrapped and start again.

Bob

hi to you both yeah it was the tich just a rod, i was going back and forth hardly any movement but it grabbed on the wind out. and if i was to scrap it (i was seriously considering it) i would of had to remake a few parts and fourtunly then it was a carbon steel tap im glad i got it out so is the wife because im very inpatient normally but last night must off been a good day

many thanks to you both for your replys

Hi Michael, I was taught that carbon taps and dies were only for cleaning or clearing threads, buy good quality hss taps and dies use the correct cutting compound and always clear the thread, half a turn forward and one complete turn back. I personally think carbon taps and dies are a waste of money.

Good luck Alan

hi alan il bear that in mind and when i get the money as i have to buy a new one i will buy hss

'fraid I must disagree - a good quality carbon tap will give you a better cut in most any material than what a HHS one will. HHS are called 'heavy handed' taps in my workshop.

hmm carbon hss cheap dear i dont know il see what my pocket can afford when i come to buying a new one

I have hade this problem on two occasions. 304 s/s part with a M4 HSS tap broken in a blind hole.

No problem. All you need is time. The broken tap is dissolve with phosphoric acid, the rust treatment

products work fine. A small amount in the hole and change it each day for about a week.

regards Kevin

I'll second that Tel a respectable carbon tap usually cut better tha good HSS taps.

One thing that i always feared was tapping 6 to 9BA in a hard metals at least 6 times the depth. Always used HSS though and lock up within 1/32 of a rev, took ages. I used to constantly swap second, starter and bottoming taps, it made it a little easier.

Using cutting oil or similar may be beneficial, other times its not, suck it and see.

The last two years i have replaced my taps with the machine spiral taps with red, blue, yellow bands, they cut great in everything but expensive.

I normally had to break up the tap in the hole.

Hi there, just to add to the debate, I have read that in gunsmithing circles (hi value workpieces and small taps) they use carbon taps so that WHEN you break one it is so brittle it can be hit with a punch and shattered and the pieces picked out. They also have a keener edge than HSS but not as durable.

Regards, Dave

Mmmmm, hand taps or machine taps? Either way I would always recommend HSS. I would also recommend drilling 0.1mm bigger than recommended in any stainless steel that is austenitic (316, 303, 304 etc...) as it allows more clearance and less material to cut - just need to go careful if a gauged size is required.

for example an M3 tapped hole in 316 stainless steel - I will ALWAYS drill 2.6 diameter hole and use quality cutting oil/compound and HSS tap.

And, yes the material would have changed by heating it up. Only really matters in critical parts though.

Edited By Andrew Sherman on 22/02/2012 12:30:15

David you can do that with HSS. No idea who wrote the book may be some back street bodger.