This calculator offers numerous options to suit several different lathes.

http://www.imagesalad.com/lathenovic...athegears.html

http://lathenovice.wordpress.com/

--
WB
..........

On Tue, 03 Apr 2012 14:29:35 -0400, Wild_Bill wrote:

This calculator offers numerous options to suit several different
lathes.

http://www.imagesalad.com/lathenovic...athegears.html

http://lathenovice.wordpress.com/

Interesting, but wouldn't work with my Smithy, which has a gearbox
between the change gears and the lead screw (said gearbox having a fast/
slow lever that changes the ratio by 2:1).

I've just got a chart of all possible combinations, with most of the
repeats winnowed out.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

"Tim Wescott" wrote in message
news
On Tue, 03 Apr 2012 14:29:35 -0400, Wild_Bill wrote:

This calculator offers numerous options to suit several different
lathes.

Interesting, but wouldn't work with my Smithy, which has a gearbox
between the change gears and the lead screw (said gearbox having a
fast/
slow lever that changes the ratio by 2:1).

The gearing isn't that difficult to figure out. If the spindle and
leadscrew turn at the same speed, the lathe will copy the leadscrew's
pitch. For other pitches the cut-thread-to-leadscrew ratio equals the
gear ratio.

jsw

I have a Smithy 1220XL, but it's been in a crate for the past couple of
years.

If one of the headstock case Hi/Low selector positions is 1:1, a gear
calculator should werk.. I can't say for sure.

Maybe you could send a copy of the chart to the metalworking dropbox:

http://www.metalworking.com/dropbox/

http://www.metalworking.com/dropbox.html


--
WB
..........


"Tim Wescott" wrote in message
news
On Tue, 03 Apr 2012 14:29:35 -0400, Wild_Bill wrote:

This calculator offers numerous options to suit several different
lathes.

http://www.imagesalad.com/lathenovic...athegears.html

http://lathenovice.wordpress.com/

Interesting, but wouldn't work with my Smithy, which has a gearbox
between the change gears and the lead screw (said gearbox having a fast/
slow lever that changes the ratio by 2:1).

I've just got a chart of all possible combinations, with most of the
repeats winnowed out.

"Wild_Bill" wrote in message
...
I have a Smithy 1220XL, but it's been in a crate for the past couple
of years.

If one of the headstock case Hi/Low selector positions is 1:1, a
gear calculator should werk.. I can't say for sure.

If not you figure out an equivalent leadscrew pitch that is 1:1 to the
spindle with equal-sized gears in the train.

Say the leadscrew pitch is 4 TPI and installing equal-sized change
gears on the banjo makes it turn half as fast as the spindle. You
would calculate threading gear ratios as though it were 8TPI.

On my lathe the quick-change gearbox input shaft turns at 3/7 of the
spindle speed.

jsw