Hard (Turning)Times

I've finally gotten around to fitting the ball screws to my small simple test CNC mill conversion, the ball screws were bough here second hand but pretty much unused and were a "close but no cigar" match to my mill so yesterday I slung them in the lathe to adjust the end dimensions to fit.
The cuts on the X axis screw were within the annealed areas but for the Y axis screw I needed to go into the hard section and didn't fancy hitting it with a blow torch and wet rag, so, after trying a couple of styles of carbide insert I remembered I had a box of CBN hard turning inserts, I stuck one in a holder and all I can say is "Knife through Butter".

Attachment 24927

The shiny bit is the Hard Turning, the rest was already done when I got the screws.

Interesting result. Is the original bit of machining as rough as it looks? I know that photographs are often misleading when it comes to surface finish. And can you use the existing thread, or are CBN threading inserts available? I've never looked past carbide in the catalogues - prices go up as you turn the pages...

And for completeness, what lathe were you using? Possibly not using the kinds of speeds/feeds/DOC that a "hobby-class" machine could achieve?

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Originally Posted by Neale

Is the original bit of machining as rough as it looks?

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Almost ;-)

Quote:

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Originally Posted by Neale

And for completeness, what lathe were you using? Possibly not using the kinds of speeds/feeds/DOC that a "hobby-class" machine could achieve?

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Myford Super 7 Long Bed, 1hp, 3 phase, at 2000rpm and 0.2mm DOC, manual feed so the material comes off like angel's hair on fire :D
My head stock is a special with 30.5mm through capacity and a native ER40 nose taper but with a register and back plates with 3 & 4 jaw chucks but I still have the standard top slide with an RDG copy of the Dickson QCTP.