Taper roller bearings in my 7x14 lathe have significantly improved performance and finish, but I notice the rpm's still fluctuate while parting or taking heavier cuts, especially with 304 stainless steel which is my favorite material. I figured this was natural because of the lathe's size but decided to investigate possible solutions to increase torque at slow speeds. I first thought of trying a more powerful motor but didn't want to risk the lathe buckling from stress that it wasn't built to handle. Another possibility was to tweak the speed/torque pots on the circuit board but didn't want an "electrical" solution over a mechanical one. The jack shaft motor speed reducer mod seemed like overkill. I ultimately came accross this simple belt and pulley kit on eBay which lowers the gear ratio and decided to give it a try.
I made a key for the new motor pulley from 35 cent 1/8" key stock and spent a couple hours installing the kit, painstakingly adjusting belt tension and took my time leveling the motor in its mount. Max speed in low gear is now down to 660 rpm and 1550 rpm in high gear which I never use. The torque increase has done several good things, most of which I didn't expect - parting stainless produces smooth chips and the motor speed no longer dips or stalls, I get an excellent finish when taking heavy cuts, the lathe no longer labors to spin up the 5" 5C collet chuck, tapping and threading with my tap and die holders is much easier, no chatter when chamfering, the dartboard/pie chart ghost pattern when facing is gone, the metal headstock gears run a little quieter, I can now run the spindle as low as 20 rpm, and I like replacing plastic parts with metal ones.
Taper roller bearings have been the best upgrade and this increased torque mod is the cherry on top.
I made a key for the new motor pulley from 35 cent 1/8" key stock and spent a couple hours installing the kit, painstakingly adjusting belt tension and took my time leveling the motor in its mount. Max speed in low gear is now down to 660 rpm and 1550 rpm in high gear which I never use. The torque increase has done several good things, most of which I didn't expect - parting stainless produces smooth chips and the motor speed no longer dips or stalls, I get an excellent finish when taking heavy cuts, the lathe no longer labors to spin up the 5" 5C collet chuck, tapping and threading with my tap and die holders is much easier, no chatter when chamfering, the dartboard/pie chart ghost pattern when facing is gone, the metal headstock gears run a little quieter, I can now run the spindle as low as 20 rpm, and I like replacing plastic parts with metal ones.
Taper roller bearings have been the best upgrade and this increased torque mod is the cherry on top.
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