The progress on the engine continues. In this episode I’ll be making the cylinder sleeves and pistons.
The cylinder sleeves are turned from cast iron bar stock. The first side is turned to finish size on the outside and inside diameters. This ensures concentricity.
After parting off, the sleeves are finished on the second side. The small shoulder will create a groove in the cylinder block for an O-ring.
Finish turned sleeves:
…and that’s how they look installed in the cylinder block:
The surface finish in the bore turned out very nice and was cylindrical within less than 0.01 mm. I contemplated to just leave it as is, just turned. But I decided to finish lap the bore. Since the surface finish was already really good, and the bore straight, the lapping took mere minutes to complete (note the cling film on the lathe bed, to protect it from any lapping compound drips).
The next parts are the pistons.
I started with turning a boss to hold the blank in a collet for the subsequent operations. The piston diameter is 32mm, too large to go directly into a 5C collet.
Chucked in a collet, the OD is turned to finish size and the grooves for the rings are cut:
Using a collet block, it is over to the mill to cut the recess for the connecting rod:
Without removing the piston blank from the collet block, the wrist pin bore is drilled and reamed. This ensures the hole is perfectly perpendicular to the milled recess.
The last operation is to face off the chucking boss. The piston is clamped very gently in the 3 jaw chuck with some paper to protect the surface from getting marked up.
The finished Pistons:
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