Virtually every modern lathe above 7 inches swing has a quick change
gearbox. When trying to get a pitch not listed on the feed/threading
chart the options are limited compared a lathe equipped with a full
set of change gears. Since I have the CNC option odd thread leads are
easy to do. But there are many times that I have a setup in the CNC
that I don't want to disturb so a one off part then has to wait a
while. I am considering putting CNC on a manual lathe and just
switching between manual and CNC. But I'd also like to know what
others do when faced with the odd lead, QC gearbox problem.
Cheers,
Eric

wrote in message
...
snip
But I'd also like to know what
others do when faced with the odd lead, QC gearbox problem.
Cheers,
Eric

I have a random assortment of change gears (some home made) for my Logan.

I can swap these out in the gear train that feeds the QC gearbox and change
the gearbox's ratios.

I usually just swap the gear on the gearbox (usually 48) with the new gear.
If I put a 54 tooth gear there and set the levers for 24tpi (1/2 of 48) it
cuts a thread of 27tpi (1/2 of 54).

Paul K. Dickman

wrote:
Virtually every modern lathe above 7 inches swing has a quick change
gearbox. When trying to get a pitch not listed on the feed/threading
chart the options are limited compared a lathe equipped with a full
set of change gears. Since I have the CNC option odd thread leads are
easy to do. But there are many times that I have a setup in the CNC
that I don't want to disturb so a one off part then has to wait a
while. I am considering putting CNC on a manual lathe and just
switching between manual and CNC. But I'd also like to know what
others do when faced with the odd lead, QC gearbox problem.
Cheers,
Eric

You mean I can feel smug that my Smithy is a piece of crap?

I just made a chart with all possible combinations of the (manual)
change gears supplied with the thing. There's something like 80000
different combinations, many of which are redundant, many of which are
extremely oddball, but many of which are rational, commonly used threads
(like 40TPI, which was my immediate need, and 56TPI, ala 2-56).

I gotta find a way to sort the list now, to pick out the useful inch and
metric threads, the 'best choice' of the redundant ones, and to
depreciate the oddball ones.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Redundant ones are for broken tooth in 'that wheel' - use redundant ratio.

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


Tim Wescott wrote:
wrote:
Virtually every modern lathe above 7 inches swing has a quick change
gearbox. When trying to get a pitch not listed on the feed/threading
chart the options are limited compared a lathe equipped with a full
set of change gears. Since I have the CNC option odd thread leads are
easy to do. But there are many times that I have a setup in the CNC
that I don't want to disturb so a one off part then has to wait a
while. I am considering putting CNC on a manual lathe and just
switching between manual and CNC. But I'd also like to know what
others do when faced with the odd lead, QC gearbox problem.
Cheers,
Eric

You mean I can feel smug that my Smithy is a piece of crap?

I just made a chart with all possible combinations of the (manual)
change gears supplied with the thing. There's something like 80000
different combinations, many of which are redundant, many of which are
extremely oddball, but many of which are rational, commonly used threads
(like 40TPI, which was my immediate need, and 56TPI, ala 2-56).

I gotta find a way to sort the list now, to pick out the useful inch and
metric threads, the 'best choice' of the redundant ones, and to
depreciate the oddball ones.



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On Mon, 28 Jul 2008 13:19:37 -0700, Tim Wescott wrote:

wrote:
Virtually every modern lathe above 7 inches swing has a quick change
gearbox. When trying to get a pitch not listed on the feed/threading
chart the options are limited compared a lathe equipped with a full
set of change gears. Since I have the CNC option odd thread leads are
easy to do. But there are many times that I have a setup in the CNC
that I don't want to disturb so a one off part then has to wait a
while. I am considering putting CNC on a manual lathe and just
switching between manual and CNC. But I'd also like to know what
others do when faced with the odd lead, QC gearbox problem.
Cheers,
Eric

You mean I can feel smug that my Smithy is a piece of crap?

I just made a chart with all possible combinations of the (manual)
change gears supplied with the thing. There's something like 80000
different combinations, many of which are redundant, many of which are
extremely oddball, but many of which are rational, commonly used threads
(like 40TPI, which was my immediate need, and 56TPI, ala 2-56).

I gotta find a way to sort the list now, to pick out the useful inch and
metric threads, the 'best choice' of the redundant ones, and to
depreciate the oddball ones.



Download Marv Klotz's program change.exe and edit the config file for the
gears that you have:-

http://www.myvirtualnetwork.com/mklotz/files/change.zip


As to the OP. Manual lathes should have a banjo at the end even if they've got
a QC gearbox. Both of mine do and it has proved useful for threads that the
designers weren't aware of/bothered with.

Mark Rand
RTFM