View Full Version : Repairing bull gear
07-04-2001, 10:53 AM
My Logan 824 lathe has chipped teeth on the bull gear. Due to the price of factory rplacements I am considering brazing the chipped areas with oxweld m25 brass rod and machining new teeth. The procedure is shown in the Linde Oxy-Acetylene Hand Book. I have used used brass rod to build up worn machine slides and it was very effective in service and easily machined. We used two men one preheating the castings with a rosebud and the other doing the brazing.My employer would give a chit redeemable at the canteen for two cartons of milk. This was supposed to counteract any toxic effects of the fumes!Not sure if it worked but it hit the spot after that hot job. Comments on this plan are appreciated. DE
07-05-2001, 05:52 AM
Yes it will work, but. Are any teeth gone? How well does it run now, I have a couple of teeth off my Logan, runs quiet enough I am not going to touch unless I have to. I also have a bigger machine I use for big stuff, I don't use back gear too often.
You might check with Meridian equipment, he has used stuff for logans.
If you do build up, make sure you recut teeth the same as the other, worn and all. If you recut to specs and not match old you will loose that tooth, experience talking here, I've made that mistake.
Story time, I have this old relic New Haven, about 1880 vintage, it has a couple of teeth that have been repaired by inserting in teeth, they are tapered and dovetailed in so that the drive pulley keeps them from coming out. Really neat old repair job.
A friend and I fixed a couple of teeth on his Logan bull gear a few years ago. From somewhere or other he got another broken bull gear and sawed out a block containing two or three (whatever it was) gear teeth. Then he made a notch in the gear he was trying to fix, and we brazed in the block. Years later, it's still working fine.
Having done that...I think if you can build up the broken teeth by brazing and then machine/file new teeth, you'll do just as well if not better. Just take your time and try for fit, meshing the gears by hand, until they run smoothly.
Another approach would be to cut slots, braze in slivers of cast iron, and machine/file those to shape. I recently fixed a gear on a tower clock that way. (It was brass, but same technique.)
07-08-2001, 12:11 AM
Thank you both for your input. I was hoping to get the seat of the pants kind info that you both have provided. I can't learn it all out of books! I am thinking of making a fly cutter for my verticle mill to machine the repair. I have a 5/8 boring bar that came with the lathe. It may need a larger slot for a tool to cut the gear teeth. I have time to plan as the current honey-do is a total kitchen remodel. I did'nt make it easy on myself as I chose to make my own cabinets with inset as opposed to over lapping drawers. Life is full of choices but I just like to go the hard route.
Thanks for your help DE
08-11-2001, 07:29 AM
I just ran into a #4 brown and sharp gear cutter yesterday for $300. Think I will get it. Could you be a first customer? Would you have a blank?