Sieg SC3 7x16 Mini Lathe Question...

[Mobile Wizard]

The lands are 30.01mm, the LMS part number is 5579. Is 0.01mm going to make that much difference. Another noob question I have is how do you set the preload on these lathes.

 

[GrifterGuru]

The lands are 30.01mm, the LMS part number is 5579. Is 0.01mm going to make that much difference. Another noob question I have is how do you set the preload on these lathes.

0.01mm can be the difference between a tight sliding fit and a press fit. I actually spun my c3 spindle in the SC3 using some 600 grit on it to get the bearings to a tight slip fit. For the SC3, I did it by hand.

Do you have replacement bearings to hand? if so, spin the spindle beteen the chuck and a live tailstock centre (I used a 60mm pipe centre), run some 600 grit paper over the lands until you get a tight slip fit. Trust me, you will be thankful you did it as it will mean no more need to press the bearings on or use a puller to remove them.

Also, invest in a PAIR of C-spanners for the tail end lock nuts, makes pre-load adjustments so much easier when you have A/C or TRBs fitted.

As for pre-load, that depends on bearing type.

If using Angular contact (A/C) bearings or Taper Roller Bearings (TRB's) yes, you add preload, but only enough that you have .0005" (half a thou) or less movement when pushing/pulling along the length of it or pulling up/pushing down vertically.

Too much pre-load and you overheat the bearings.