1.5" 6tpi thread for Harisson chuck

hi there i need to cut a short (12mm length) internal thread for a ER32 collet chuck i have made. i do have a tap of the correct size but not enough depth to run it down.

so am i best grinding a tool up or is there an insert i can buy?

thanks

chris

I think you might have made things I the wrong order! First screw cut the internal thread in the blank, then mount the blank by the thread on the spindle nose to turn the interval taper and the closing nut thread. I don't think you would have a chance of tapping a thread of this size true, or even screw cutting it. The thread is probably 55 degrees and you can buy inserts.

HI Chris, I agree with John H as far as getting the cart before the horse !! however it still may be possible with careful setting in a 4 -jaw, difficult to advise fully without seeing the job.

As for the tool since its a one off job would grind one from HSS and use it in a substantial boring bar, assuming there is a shoulder inside the work I would arrange to start inside with an undercut and screw-cut outwards L -R just make sure you are cutting a RH thread !

Because of the size I would also arrange things so as the thread gets deeper you can feed in say 2 thou on the cross slide and 1 thou on the top slide thus reducing the cutting load on the tool.

Might be wise to make a male gauge first to test the work.

John

Good advice above and you may be able to correct the ER taper afterwards if necessary.