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

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.

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