< Connecting Rods >
The jig for the coupling rods is useful again because the bush spacing is equal. To cut the tapered profile of the connecting rod, the rod is tilted on the jig. The picture shows how to do it - the pin OD in the jig is left smaller than the big-end ID.
The flute is also tapered but the taper angle is smaller than the outer profile. Therefore I put a thin bush between OD and ID when cutting the flute.
A mild steel blank is drilled and reamed in the lathe.
Cutting out with drill.
Note two pairs of big holes at both ends. They are for radius of "neck" at both ends.
Finishing the big-end on the rotary table.
I changed the big-end's profile from round to square.
Cutting the side.
After that, the bottom edge is cut out by metal saw (same as the coupling rods).
Finishing the upper and the lower surface.
The job is tilted as previous picture.
Reducing the thickness of the small-end to the side-cut thickness.
To erase the step completely, I controlled 0.01mm depth with DTI and finally ground with the oil stone.
Cutting the flute.
First, the rod is tilted in one direction and cut to final depth. After that, without moving the stage, the rod is tilted in opposite direction and cut again. It means that the cutter traces "V" shape on the rod.
Finally oil cup and cotter pin are attached to the big-end for detailing, and phosphoric bronze bushes are press-fitted.