Intermediate Shaft Spigot

This part is a steel stub which secures the inner race of the rear intermediate shaft bearing. The outer race of this bearing is inside a bored gear. The fit is essentially permanent and was designed as an interference fit. It is also held by a cap screw, in my case, 10-32.


  a 5/8" stub of 4140 steel was chucked, and the ball bearing portion carefully turned. There is a very small shoulder which rests against the inner race and thus prevents the rotating outer from rubbing against either the major spigot diameter or the gear case.
There are a lot of bearing-critical diameters to create in this project, either turning or boring. Each must be done with precision, or gear and/or bearing life will suffer, as well as create a noisy gear train.
With the bearing stub turned and polished, the spigot was drilled and tapped through 10-32. The setup here is typical for best results... in the tailstock is a spring-loaded center which creates pressure on the tap, as well as holding it truly straight.
With the spigot tapped, the rear portion of the spigot is turned for the press fit into the gear case. In my case, I turned mine to .2506 for a .0006" interference.
The spigot, ready to install after I clean off the swarf!

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