# Metric Transposing Gears For 9c



## Surprman (Jun 27, 2015)

I have a need to do some metric threading on a project I am working on.  I saw this link and figured it would be a nice way to do short some short length metric threading (the error is only 2 parts per thousand or ~2 threads per meter - good enough for threading things an inch or two long!): 

http://ixian.ca/gallery/metric/metric.htm

I bought an extra 56 tooth gear on EBay (the one I had was not flat)

Turning the bushing was fun and when I was done I made a test part with 1mm threads.  It came out great- now I can do metric threading if I need to!

Rick


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## brino (Jun 28, 2015)

Nice job,

So far I've only cut imperial threads on my Southbend, but I know I'll need metric ability in the future.
I have done no research into it, but I have book marked this thread for reference.

Thanks!
-brino


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## spongerich (Jul 4, 2015)

I found this someplace for the SB Model A and have used it a couple of times and the threads I cut were an excellent fit.... 
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Buy a 54 and an 80 tooth gear from the normal 9B/9C set.
If you remove the current 20 and 56 tooth gears from the end of the lathe,
and replace with 54 and 80 respectively, you will turn the gearbox at 1.89
times its normal speed. This will make your 8tpi leadscrew act like it is 4.233
tpi. This happens to be 6.00075 mm, which is 6mm with 0.0125% error.

Now, your gearbox can be used to cut 11 metric pitches.

mmpt gearbox
0.25 192
0.30 160
0.50 96
0.60 80
0.75 64
1.00 48
1.50 32
2.00 24
3.00 16
4.00 12
6.00 8


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