Threading tools

[Alan]

Hello Chaps

I about to take my first steps in to "threading on the lathe" It seems that the usual set up is a tool with 60 degree angle, set at 90 degree to the work but being set on the cross slide with an angle of 30 degrees !!

However I see that you can buy Glanz type tools for threading with replaceable inserts, does one therefore set these tools up the same way as a normal threading tool (as above) or are they set up like a normal turning tool ie without the 30 degree angle with the appropriate angles being manufactured into the inserts?

I am also going to try internal thread cutting but I don't know the set up rules with regards to this.

As always help and advice is welcome

Alan

[SteveW]

Alan,

I've always gone for the top slide at not-quite-half-the-tip-angle by almost a degree and zeroed the cross slide. This ensures the tool cuts on both edges (just) so maintains the thread groove at the tip angle.

The advantage I've found using the top slide to add cutting feed is you can use a full turn on the cross slide to whip the tool out promptly with one full turn. It's just a matter of re-zeroing before starting the next cut (AND REMEMBERING WHICH DIRECTION TO TURN).

A while back a new member reported problems when using some threading tips, the thread was too loose. You need to ensure the tip radius suits the core diameter you're expecting. If the tip is too rounded the valleys will be too wide having meet the correct core diameter

If the tip is too pointed you need to advance the tool towards the headstock a few thou at a time until the thread valley width is correct. This is easily done by backing out on the cross slide while driving in on the cross slide. If you do the math you can move the tool side ways without reducing the thread core any.

[ettingtonliam]

Alan
The tool tip is 60deg for US and Metric threads, but 55deg for Whitworth form which includes BSW, BSF, Brass, Gas, Cycle and ME series of threads. With whitworth thread form, the topslide angle is 27.5 deg (Half 55deg).
Regards
Richard

[Alan]

Thank-you both Gentlemen,

Advice much appreciated.

Alan

[maninshed]

When I screw cut I always have the compound slide parallel to the work piece, and use the cross slide to apply depth of cut. I then use the compound slide to apply a side cut of a thou or two, so the tool is not cutting in on both faces. If you a bit bereft of mathmatical knowledge it saves having to work out the angle to get the correct depth of cut on the compound slide.