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Jon Elson[_2_]

wrote:
On Jul 24, 2:23 pm, RoyJ wrote:

I just had to jump in with a mildly off topic response: Yesterday I was
showing a student how the edge finder did the 'jump' when it contacted
the surface (and the usual discussion about the .0005" to .001"
difference from the 'real' edge) when the jump went the wrong direction.
!!@##@!!! I had been running it in reverse! cue to very red faced
instructor.

Was it a Bridgeport? - the ones at my college do that, when you go
from H to L range, on one of them you need to reverse the motor.....I
have to work it out each time.....why its done that way, no idea......
It's just the way the back gear train works. A lathe back gear inserts
two reversals, so the spindle ends up going the same way. The
Bridgeport uses a belt drive to turn the back gear, so engaging the gear
only inserts one gear train reversal, so the spindle ends up running the
other direction. You get used to it if you use it often.

Jon