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!|
TurboProp | Home