OT- small diameter turning

I just asked our manual lathe guy if he could turn a piece of 1/2 hard brass .012" dia x .13 long. He said "yep, no problem, done them before" !!

Anyone else doing turning that small?

Mike1974 said:

I just asked our manual lathe guy if he could turn a piece of 1/2 hard brass .012" dia x .13 long. He said "yep, no problem, done them before" !!

Anyone else doing turning that small?

Click to expand...

With no tolerance on straightness, roundness, or diameter, sure I can make it.

TeachMePlease said:

With no tolerance on straightness, roundness, or diameter, sure I can make it.

Click to expand...

With a belt sander..??

Mike1974 said:

I just asked our manual lathe guy if he could turn a piece of 1/2 hard brass .012" dia x .13 long. He said "yep, no problem, done them before" !!

Anyone else doing turning that small?

Click to expand...

0.012" ?
Ha, that qualifies as a bar stock

This was about 14 micrometers or 0.00055 inches in diameter:


Any smaller than that and you need damn electron microscope to set the tool center height

rest of the thread if someone is interested: Digital microscope for lathe work

Any watch repair person, the kind that can make balance staffs, not just replace batteries, can turn and polish hardened steel to around .005 inch diameter. Smaller diameters would seldom be needed, but I never did a ladies' wrist watch staff, so I don't know their dimensions.

The trick is to have a good lathe that turns at high speed. A Hardinge lathe with a 5C spindle and 3500-4000 RPM can do surprisingly small work. Hardinge makes 5C collets with stock size order holes as small as 0.016", 1/64" or 0.5 mm. But watch lathes are much smaller and faster and watch lathe collets are made with order holes as small as 0.1 mm.

Turning brass to .012" x .13" is a trivial job for a watch lathe with a slide rest. I will explain that most watchmakers never use a slide rest because most watch work can be done with hand-held tools faster and maybe even better.

Larry

I calculated the RPM needed to run that part at 1000 sfm.

314,000...!!

I routinely do balance staffs for very small high end watches, length around 2.2mm is common (.087"), sometimes as short as 1.6mm (.063"), pivots on those are typically .065mm or .0026". 2 pivots, one at each end, largest diameter on the part would be 1.5mm typically with about 4 other diameters and a critical taper.

That's in steel, would be tricky to do in brass but .012" in brass a piece of cake.

And that is why smaller lathes, with higher spindle speeds, are generally used for such work. In my shop I would use my Unimat instead of my SB.

But then, I consider such calculations as guidelines, not rigid dictates.

ChipSplitter said:

I calculated the RPM needed to run that part at 1000 sfm.

314,000...!!

Click to expand...

Heck I can do that job with my harding 5/9 lathe. Key is to start with 1/4 inch stock and take it all off with one whack.
Dead sharp tool, too.

OK I cheated a bit, I used the antique lathe for this, also I screwed up and made it
too long. Have to get a heavy duty set of cutters to short it to 0.130 inch long.