Thread Milling

[richardandtracyParticipant @richardandtracy]

John,

I'll see if I can do it sometime week beginning the 16th. Can't do it before then due to some deadlines I can't miss.

Regards

Richard

[John HaineParticipant @johnhaine32865]

No hurry for me Richard, I have done the thread I needed for the moment. But having discovered that thread milling can be so straightforward I think I will be doing a lot more.

[richardandtracyParticipant @richardandtracy]

Fortunately I commented the old code out, rather than deleting it. Just need to put in a 'switch' statement, a radio button group and apply some of the other updates to the old code to bring it up to the same spec as the current bit, so shouldn't take too long once I can get to it.

Regards,

Richard.

[John HaineParticipant @johnhaine32865]

I just thought I'd post an update on my experiences with thread milling, now that AT LAST I've managed to cut a thread correctly in the ER16 collet chuck blank I'm making for my new (to me) Unimat. Needed to make an M14 x 1 socket with 5x14mm register. Richard kindly helped by supplying a version of his code (now I think the standard on his website) that can either climb or conventional mill a thread – climb milling not being likely to work with a modified tap cutter.

However at the recent London exhibition I bought a nice small bore internal inserted-tip threading tool from the excellent JB Cutting Tools, so that if all else failed I could make the thread in the lathe. It turned out that the tool tip was exactly on the lateral centre line of the bar, with an effective diameter to the tip of 10mm, so it ought to be usable as a thread mill, and being single-point able to climb mill as well. And as a general purpose 60 degree tool able to cut any pitch as long as the diameter is more than about 11 mm. Alas, the tool doesn't seem to be listed on their website.

So I had another go, the tool cut fine but the thread was far too big – turned out I'd typed the wrong diameter into Richard's program, 9mm instead of 10mm, so not surprising. Finally made a new blank yesterday, milled it this evening, nice smooth fit onto the Unimat spindle nose, job done. The thread looks very clean, and cut with no drama.

So thread milling works really well, and now I have the technique I think it is much easier than doing internal threads on the lathe, largely because setting the tool to the centre line and controlling depth of cut is very easy. Looking at a couple of other insert-tip boring bars I have, the edge on the centre line looks like a standard feature, so at least as long as you can get a small enough bar to fit your hole they should be usable as thread mills. For smaller threads you can always modify a tap, or buy a purpose-made thread mill.

Many thanks again to Richard for modifying his code (though in the end I didn't use the "screw down" feature), and I can recommend his application for anyone wanting to give this a try.

[Author]

Posts