On Fri, 28 Oct 2005 19:52:49 -0500, Jon Elson
wrote:

Eric R Snow wrote:
I know that most lathes have a powered X axis. But the gear ratio is
really high. On one lathe in my shop the X axis advances about .014"
on the diameter for each revolution of the grooved rod that supplies
power to both axes. This guy needs about .320" on the diameter. So if
I was to use the power feed the grooved rod would need to spin 23
times as fast as the spindle. With the gears in my lathe I can't do
this.
On the 10 and 12" Atlas lathes, the crossfeed was exactly equal to the
logitudinal feed. On my Sheldon R15 lathe, the crossfeed is 1/2 the
longitudinal feed. I've never seen a lathe where there was so much
reduction from the leadscrew to the crossfeed screw. That doesn't
make much sense, as it would require the leadscrew to turn pretty fast
when roughing a facing cut at higher spindle speeds. I can't recall
a lathe where the ratio was far outside the range I quote above of 1:1
to 2:1. Just curious, what lathe is that that has this high reduction?

Jon
This particular lathe is a Jet 1440. 14 inch swing, 40 inches between
centers. This lathe is a copy of a Clausing, I think. Like all the
larger lathes I've run, Sheldons, Clausings, Howas, etc. this one has
a lead screw for threading and a separate grooved shaft for power
feeds. One revolution of this shaft equals about .014 for the
crossfeed and about .019 for the longitudinal feed. This is normal.
And it does make sense. It lowers the torque on the gear train in the
headstock and the shaft that turns the gears in the carriage.
ERS