The Piston, #S331-F
The piston comes as a nice piece of round cast iron, looks like a piece of continuous cast Dura-Bar, who knows.

It mounts to the piston shaft with a ¼” per foot taper and a nut. I need to set the compound to cut the taper. I made a sine bar table to hold a 5” sine bar and stack just for the purpose of setting the taper on a lathe. The first pic shows the adjustable bar being set parallel to the Z-axis, no travel on the indicator as the saddle traverses the bed. The next pic is with the sine bar and stacks to set the taper. The compound is adjusted until the indicator indicates no travel while the compound is traversed. Since I’ll use the same lathe and setup for the piston shaft, this degree of precision is not really needed, but it makes the part interchangeable with any that are made to 1/4” per foot. The stack needed for 1/4” / ft is ~ 0.0521”.
S331-F-Piston-1.jpg, S331-F-Piston-2.jpg
Swapping a 5C mounted chuck for the collet, the CI lump is indicated in and roughly turned to size. It is drilled and then bored for the taper. The piston is remounted to turn and face to roughly size and bored for the nut clearance.
Once the piston shaft is made, I’ll mount the piston and finish the piston to size.
S331-F-Piston-3.jpg, S331-F-Piston-4.jpg
The Piston Rod, #S331-E
I cut off a 5” piece of 5/16” SS 303 stock and mount it in a collect. The print calls for 316, but what I have is 303.
The print shows 3/8” for the length of taper and remaining 3/8” is threaded. Nowhere does it indicate the thread size, but it seems a bit obvious 1/4” is a good choice. Once the threading is done, I cut the taper for the 3/8” length until the piston is fitted.
S331-E-PistonRod-1.jpg, S331-EF-Piston-n-Rod-1.jpg
With the nut tightened, the piston is finished to final size.
The piston rod was faced on the crosshead side, measured from the shoulder for the piston, and the drawing’s measurement subtracted from the actual length. Then a little dye-chem and the distanced marked from the crosshead’s end. In the lathe the mark was aligned with the facing bit with a 10x loupe and the DRO set to zero. After facing to spec, the piston rod is finished.