View Full Version : Metric Transposing Gears

02-17-2005, 05:21 PM
Does aneyone have information as to what gears are needed and where, to allow metric thread cutting on my 10" gear box equipped South Bens Lathe?
If so, please advise.

Paul Alciatore
02-17-2005, 09:26 PM
The main gear you will need is a 127 tooth or a 127/100 compound or one of the approximation pairs like 47/37.

There are some places that sell them. Do a web search for "metric change gears" and "South Bend".

After the basic translation to metric, you may need additional gears to allow specific metric pitches, depending on the English pitches your gearbox provides. I have a spreadsheet that translates the gearbox threads to metric with a metric compound. It can be expanded to add additional threads with a second compound between the stud gear and the gearbox. If you can provide some more specifics, I will try to work out some combinations for your lathe. E-mail me.

Paul A.

02-17-2005, 10:50 PM

What model SBL do you heve?

I just got done with a spreadsheet for my 10K model A and would be happy to share.


02-17-2005, 11:11 PM
What is the pitch(how many threads per inch is your lead screw here is the chart for an eight pitch lead screw


If your lead screw is not 8tpi I have other pic's


02-20-2005, 07:18 AM
Thanks for the responses.

If seams that answers create additional questions.
From the chart, it looks like several stud gears are needed. Is that true with a QC gearbox?
After I install the 100/120 gears, what contribution does the gearbox make to different metric pitches?
My lathe model is: CL 187A. What is a 10K?
My current project is a 1.75MM thread. In the past and I am sure in the future other metric pitches will need to be cut.

02-20-2005, 06:51 PM
If your lathe has 2 stud gears A 40 T for the top line on the threading chart and a 20T for everything else and has a 1 1/2-8 spindle nose it is probably a 10K.

I worked out a method to reduce the number of stud gears. You NEED a 127/100 compound gear or something close to it and for 1.75 pitch you need to rearrange the gears you have.

For 1.75 pitch use a 20T stud gear, the 127/100 compound gear, and your 40t gear as the gearbox gear. Set the gearbox to cut 16TPI and you are set.

FORGET about using the thread dial if wou have one.

The 127/100 gear will be interesting to find. I plan an using the method described in PIM Dec 1998 by Terry Sexton titled " a claytons change wheel"

Hope this helps,


Paul Alciatore
02-24-2005, 02:26 AM

If it was you who e-mailed me, I have been having trouble answering. It comes back as undeliverable. It may be your spam blocker.

Try putting me on your OK list and e-mail me again. I believe I can help.

Paul A.

02-24-2005, 08:55 AM
hi JDC,
If you look at the chart, you have to shift the quick change's 2 levers to specific settings for example;

for 1.5m/m pitch the stud gear is changed to 48 tooth gear, then on the quick change, the range lever is set to "C", then the tumbler lever is set to hole #1
for 1.75m/m pitch the stud gear is changed to 28 tooth gear, then on the quick change, the range lever is set to "B", then the tumbler lever is set to hole #1
for 2.5m/m pitch the stud gear is changed to 40 tooth gear, then on the quick change, the range lever is set to "B", then the tumbler lever is set to hole #1

You are required to do some lever changes to your quick change box as well as also changing the stud gear.


02-25-2005, 09:01 AM
I have a new 127/100 metric gear set for South Bend 9 or 10K South Bend lathes on ebay now starting at $ 99.95 . # 8172147547