Somebody told me that inside each piece of rusty cast iron there is a part waiting to get out so I took the top off of this bit but could not see a steam engine cylinder inside but thought I would carry on anyway.
After cleaning up all the surfaces a bit oversize I popped it in the 4-jaw and drilled then bored it out to the required 1.75"
Then back to the mill and using a nice sharp cutter with a small overlap and shallow depth of cut took the port face down to the required size, the pattern is just visual, I can't feel any steps on the surface so should have a good surface for the slide valve to run on though it will get a final rub on fine wet & dry.
The majority of the waste where the ports go was removed by drilling.
Then milled out to final shape.
Finally, the stud holes for the steam chest were drilled and tapped. Following that the exhaust passage was drilled in to meet the central slot and the two tapped holes for the pipe flange done. One thing that these pumps all seem to feature is an exhaust connection on either side of the cylinder with the one not in use being fitted with a blanking plate, so both sides were treated the same.
A big bit of the waste was rough milled off the two corners, cylinder cover stud holes tapped and then the cylinder set at an angle to have six 1/8" holes drilled down to connect the inlet port to the cylinder end. I started the holes with a ball nosed cutter to save the drill from skidding about on the sloping surface.
I then milled across to join the holes as far as the milling cutter would reach.
Setting the cylinder to run true on the rotary table the top and bottom flange were rounded to shape at 2.75" dia.
The R/T was then set up in the vertical position with the tailstock bearing on a quickly knocked up plug in the cylinder end. Using a hand ground radius corner cutter the area between the flanges was cut away to form a space for cylinder lagging material. As this surface will never be seen I just cut at 4degree intervals (one turn of the handle) which did not give a bad finish. Also cut conventional one way and climb cut the other to save having to wind the hand wheel quite so much.
The vice was then mounted on top of the rotary table and the two exhaust flanges milled to their profile.
Looks like it is true as I did find a steam engine cylinder in that block of iron and only one goof.
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