The primary gear train on my 1941 South Bend lathe makes a lot of noise. I believe the biggest culprit is the sliding gear, but the spindle gear is also very worn. I can’t find an exact replacement, but found something that is the correct tooth count, diametral pitch, pressure angle and diameter. But, it’s not as thick (1/2″ vs 11/16″) and has a smaller bore at .750″ and I need 1.437″. So I decide to modify the new gear to see if it helps with the noise.