< Main Cylinder 1 >
Next I tackled with the cylinder covers. The photo shows castings of them. Front cover casting has spigot to chuck in three-jaw. Back cover casting is unified with another component 'tail rod box', which will be cut off from the casting. All covers have eccentric bosses to catch cylinder safety valves.
I started with the front covers. Chucked with a spigot, side and inside faces are cut and finished. The center recess is a clearance for piston secure nut.
After that the spigots and eccentric bosses are turned off. Note two of them (for outer cylinders) have center projections as bolting faces for the tail rod boxes. Prototype's piston rod is designed to go through front cover and held by a tail rod box. I have no intention to reproduce it but I will make dummy tail rod boxes.
Next is the tail rod box. Chucking the back cover part, foot side of the tail rod box is machined.
Side windows of the tail rod box are opened by end mill. Later, they will be finished triangular by thin round file.
After some additional cuts for detailing, the tail rod box part is sawn off.
Here I prepared drilling jig for the tail rod box. The inner one is it and the outer one is drilling jig for the cylinder covers. Both of them are made from steel round bars.
The tail rod box is drilled through the jig, then the front cover is drilled through the box.
The tail rod box is bolted onto the front cover. Chucking the front cover part, opposite end of the box is machined.
A small bush for tail rod case is bolted on front face of the box. The bush is turned from a brass round bar. Other small screws are added for detailing.
The tail rod case is made from a steel bar. The full size tail rod (front end of the piston rod) itself can be seen through a window in the box. In the model, the tail rod case goes through the box and its back end is turned down to the tail rod's diameter to imitate it. The tail rod case with dummy tail rod is secured with a set screw in the box from underneath.
Finally the cylinder back cover is machined. Inside face is cut in the same manner as the front cover, but the center hole for piston rod is drilled and reamed.
The slide bar bolting face should be finished truly parallel to the center hole and in desired height from the center. I prepared a jig with angle plate and round bar. After roughing cuts, the end mill is adjusted to a final height. Then all of three back covers are finished in the same height.
Again back cover is chucked in the lathe. Cavity for gland is opened with a boring tool. I intend to use O-ring for sealing.