On a mini-lathe and I'd imagine on plenty of
other, less-expensive lathes , the reduction from the spindle
to the lead screw is too coarse for really fine feeds. Not only that,
it
depends on what change gears are installed. Not good.
To tackle that, one needs to drive the screw through a separate,
dedicated, low RPM, high-torque motor. When driven like that,
the screw is disengaged from the change gears.
here's the original idea: http://www.varmintal.com/alath.htm
Ever since I saw it, I thought that adding variable RPM and being
able to reverse the direction of the feed would be nice to have.
So a few days ago I ordered this:
http://www.surpluscenter.com/item.asp?UID=2006060720144702&item=5-1257&catname=electric
It came in today and I wasted no time mounting it onto my lathe.
About 1 hr later it is all done and works GREAT. I followed Al's
way of mounting it, more or less. If there's interest I will post a pic
of what
it looks like.
Being DC, it is easy to reverse (DPDS switch does the trick)
and having a variable voltage DC supply allows you to go from
0 RPM all the way to 35, with a whole lotta torque. I was able to
reduce OD of a .500 12L14 round by 3/16", in one pass, no hesitation,
motor stays cool. If one wants to simplify, pay $1 at a flea market for
something like 12V/500ma supply and you will have around 15RPM
at the lead screw, which is plenty fine.
other, less-expensive lathes , the reduction from the spindle
to the lead screw is too coarse for really fine feeds. Not only that,
it
depends on what change gears are installed. Not good.
To tackle that, one needs to drive the screw through a separate,
dedicated, low RPM, high-torque motor. When driven like that,
the screw is disengaged from the change gears.
here's the original idea: http://www.varmintal.com/alath.htm
Ever since I saw it, I thought that adding variable RPM and being
able to reverse the direction of the feed would be nice to have.
So a few days ago I ordered this:
http://www.surpluscenter.com/item.asp?UID=2006060720144702&item=5-1257&catname=electric
It came in today and I wasted no time mounting it onto my lathe.
About 1 hr later it is all done and works GREAT. I followed Al's
way of mounting it, more or less. If there's interest I will post a pic
of what
it looks like.
Being DC, it is easy to reverse (DPDS switch does the trick)
and having a variable voltage DC supply allows you to go from
0 RPM all the way to 35, with a whole lotta torque. I was able to
reduce OD of a .500 12L14 round by 3/16", in one pass, no hesitation,
motor stays cool. If one wants to simplify, pay $1 at a flea market for
something like 12V/500ma supply and you will have around 15RPM
at the lead screw, which is plenty fine.
