The Steam chests and covers have been machined as matching pairs to depth, height and width. In front of them are three bits of bar destined to become crossheads
In theory the piston/crosshead is a forged casting but not with these engines
so I am taking the opportunity to make the piston rod out of stainless steel and to use those bits of EN1A as crossheads. If you have the casting then most of the piston rod and crosshead can be turned between centres
The rod part started as 12mmm diameter Stainless, turned to length, with a shoulder to go in the crosshead and a bit for the threaded section left on the end. The top slide was set up using the gash end of the stainless bar until I got the taper required. Then it is a case of turning the taper down until it blends correctly at the correct depth with the main rod and the bit that is going to be threaded.
Before anything moves the pistons tapers need to be machined and all of them fitted on the rods. So back to the three jaw and mount up the (still over diameter) piston ready for boring the taper.