View Full Version : cutting 30 threads per inch

10-28-2003, 08:24 PM
I need to cut 9/16-30 Whitworth threads with my 9 SB with a quick change gear box. There is no 30TPI so how do I do it?

10-28-2003, 09:10 PM
You will have to change the stud gear. You can calculate the number of teeth needed, or contact South Bend, and they may tell you. They will probably be very happy to sell you the necessary gear.

10-29-2003, 12:21 AM
FWIW...& not much help for u ,unless u have access , but the atlas /craftsmn quick change box has the 30 tpi available ,remembered from the win. model 12 thrds i have cut......ck w/ ur buddies

best wishes

10-29-2003, 02:11 AM

Docn, you have been spending too much time either text messaging or on ham radio http://bbs.homeshopmachinist.net//smile.gif

10-29-2003, 02:12 AM
Marvin Klotz' site has a program you can
unzip that you can plug in the gears you
have and TPI needed and calculate the closest match. Change.zip
www.geocities.com/mklotz.geo/ (http://www.geocities.com/mklotz.geo/)

Ragarsed Raglan
10-29-2003, 07:14 AM

Have you got a 10tpi, or a 15tpi shown on the gearbox? If you have, then if you reduce the input gearing by 3:1 you can use the 10tpi selector position or a 2:1 reduction will allow the 15tpi position to be selected.

Other tpi's will produce the same results with respective gearing.


[This message has been edited by Ragarsed Raglan (edited 10-29-2003).]

10-29-2003, 08:10 AM
For some reason, South Bend seems to have skipped the 15 thread combination. That is why a calculation is necessary. You need to know the leadscrew TPI, and the tooth count of the gear train to work it out. Klotz site may help. S/B can also.
Tony's lathe site or Yahoo groups probably have info. also.
BTW, Good to see you back docn8. Haven't tried making a chamber reamer yet, but at these prices, I'm not far from it.

[This message has been edited by JCHannum (edited 10-29-2003).]

10-29-2003, 01:07 PM
There is/was a standard South Bend gear available to do this, as it also allows you to cut 27tpi for 1/4-27 pipe thread. I don't recall offhand what the number of teeth on the gear is, but SB should indeed be able to help you out with this. I think the SB book "How to Run a Lathe" may even talk about this.

10-30-2003, 10:59 PM
Thank you for the help. All I really needed to do was look at my Enterprise lathe and find it has a 30 pitch setting.
Thanks again