Precision Engineering Details

This is a newly machined 47/37 transposing gear set which converts your 8 TPI lead screw to a 2.5 mm pitch. The thread’s crest-to-crest or lead error is only 0.02% (about 0.0025 inch for a one-foot long threaded rod). These compact transposing gears are under 3 inches in diameter, leaving plenty of room for closing your factory gear cover without interference. You can find lots of good information about the 47/37 transposing gears on the internet. I encourage you to google it.

I manufactured these specifically for the South Bend 9 Model A lathe featuring a quick-change gearbox. The transposing gear system will interface with other South Bend 9 models as well, but this exact kit layout is fine-tuned for the 9A. The gears have a diametrical pitch of 18, are meticulously sliced from rugged 6061 billet aluminum, and include the matching custom installation bolt and bushing.

With the included gears and the 56 tooth screw gear, and the 20 and 40 tooth gears that should already be on your South Bend 9A, you can cut all the ISO pitches along with other non-standard pitches by changing the stud gear and setting the quick-change gearbox to the correct setting.

Supported ISO Pitches

I will include a spreadsheet showing the settings for the stud gear and gearbox, which can also be found on the internet at bnordgren.org/files/metchart2.xls.

If you have questions email me at kane@monroelawncare.com and I'll answer them to the best of my ability. If you need a photo of the actual setup on the lathe I can furnish those also.