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South Bend 9" Back gear repair kit--For Sale


Something for the South Bend Forum world to Ponder.

This is for the individuals who have a 9” South Bend lathe with a backgear that needs a small gear repair. Many gears have been repaired using different approaches. Brazing, drilling holes for screws, milling a slot for a piece of metal and brazing that in place and then filing a tooth form. All time consuming and in some cases extremely frustrating. Having a gear for replacement is an option that can be performed on the SB 9 and can be done in less than an hour. That includes removal and reinstalling the backgear! No brazing, no arbor press needed, no heating, no filing a tooth form. Just remove the old gear from the backgear and install the new 24 tooth 16DP 14.5PA 5/8” face width gear. And all you need is your SB 9 to do the machine work. A SB 9 does not need a backgear installed to work. Remove the guards and backgear then replace the guards. Place the large end of the backgear in the chuck and support the small end with the tailstock. Since the backgear bore is 3/4” you will need an appropriate center for the tailstock. Most MT 2 live centers will work. If you don’t have one you can machine a plug that will fill the bore and provide a center for a MT 2 dead center. No need to make arbors. Keep it simple. This won’t take long.

I have seen many backgears that the small gear is 5/8” face width. Some of the newer SB9s have a small gear up to 3/4” face width. I have never seen a SB 9 with a bull gear wider than 5/8”. They must have attempted to strengthen the small gears through width??

The average backgear shaft is about 1.320” in diameter. As stated above its bore is 3/4”. It is very robust. To install a new gear, the gear along with some additional material must be removed. The gears that I have for this repair have a 1.125 bore. They are steel. If you can hit a measurement of 1.1235 on the backgear shaft your home free. I use a slip fit for the gear installation. I use Loctite 680 retaining compound to secure the gear to the shaft. After 10 minutes the gear won’t move. After a 24 hour cure time it is permanent. No timing of the gears is necessary. After testing a few gears on shafts with different shaft clearances Loctite 680 holds remarkably well. Something else will break before that gear spins from the Loctite failing!

Now, someone will question the material removed from the end of the shaft to the gear that was not replaced with the gear. Here you can play all you want. Make a ring with a 1.125 bore and Loctite 680 it to the shaft. Face it off with the end. It is purely cosmetic. You can use brass, steel, aluminum or whatever you want. You can leave it alone if you want.

Why pay anyone to do this when you own a machine that can make itself. This repair is simple, cost effective and permanent. The gears run smooth and quiet. For the basement guy or weekend machinist this will give you the warm fuzzy feeling of accomplishing a gear repair without hassle.

And for the guys with extra backgears with broken teeth taking up space on the shelf, here is an easy fix to turn them into cash on fleabay.

Review the pics posted showing how the repair was done. I have gears for sale with the Loctite 680 needed for the repair. The “kit” will be $45.00 shipped. Paypal, check or money order is OK. You choose. Any questions PM me. No I do not want to repair yours.

A few forum members may have a different approach and have a complete machine shop at their disposal. This repair dosen't require any machinery other than the lathe the backgear came off. I have repaired more than a dozen backgears using this method and have not had any failures. You can buy 16DP gears from various vendors but finding ones that have a 5/8” face width with the 1.125 bore is the problem. The ones I have are ready for installation.



I put it in today and gave it size on size fit with the loctite. Thanks for developing this tommy, it's slicker than!

Now I have a oem back gear shaft that's a spare if someone needs it. Or mayhaps I'll flog it off on ebay.

rusty old tools

New member
This is a very smart repair, I did similar with a bevel gear in the gear box of an unmentionable “A” machine, I used that particular machine to effect that repair as well. I will keep this in mind should I manage to blow up my back gear.


New member
Just received the repair kit. The replacement gear is very nicely fabricated. It will be a couple of weeks before I can get to the repair. Here is a pic of the new gear next to my 9A backgear with the broken tooth.

Backgear repair kit.jpg

Many thanks to Tommy for the kit design, quick response and shipping!