Unimat SL Turns at a Taper

[BigTup]

I just got a Unimat and tried turning a 3/8" brass rod. With a micrometer the turned bar is .003 off in only 1". Bigger at the end, and not the chuck side. There is the indexing pin in place, and the drawing in the manual shows a locking screw but mine does not have that. How to dial this head in?

 

[Ulma Doctor]

Unfortunately taper turning is what unimats do.
You can try to install a snugly fitting carbide blank into the spindle through hole extending beyond spindle as far as you wish ( longer is better ) and indicate the length . Adjust the headstock retention screw ( you will need one if there is not one present ) after correcting 1/2 the error.
rinse and repeat until you are satisfied .

Something to consider, make sure sharp turning tools are on center to get the best results .

poorly adjusted spindle bearings can create deflection which may add to the taper

 

[markba633csi]

You need the locking screw underneath that locks the head to the bed- without that all bets are off

 

[BigTup]

Thanks for the input. I don’t have a locking screw. The drawing in the manual shows one, but the view is from the tailstock end, so I can't tell exactly where to install one. If someone could send a photo that would be helpful. I suppose I could disassemble the head and determine where it should be.

 

[BigTup]

I found the locking screw, and with trial and error I got the turned bar within .0005 in 3" of length. Close enough.

 

[Ulma Doctor]

I’m happy that you got’er dialed in