Part seven by Jason Ballamy

The most economic way to make the con rod was to use some 1.5" round 2014 stock rather than square or rectangular.

Two bits were squared up for the rod and cap and then drilled and tapped. As the rod has to be assembled with the crank in situ the bolts need to have their heads towards the little end so a couple of rough recesses were cut so the bolts could be put in position.

With the two parts now now screwed together the big end hole was drilled out and then using the boring head opened up to finished size.

Following which the little end was drilled and reamed for the wrist pin.

Using a milling cutter that had the corners rounded over the two cuts were made to taper the rod.

Using a fly cutter the big end was reduced down to the finished thickness

Then with the little end mounted on an arbor held in a chuck on the rotary table it was rounded over first with a 10mm roughing mill

Then cleaned up with a long series 4mm dia cutter to remove the ribs left by the rougher and also to get a smaller internal radius where the end meets the rod sides.

No pics of the next bit which was to hold the arbor in the lathe and turn tapers on each end of the now round little end but you can see it in the next shot where I am using a 4mm ball nose cutter to shape the big end.

The sides of the rod were then tapered blending the cut into the two end cuts.

To reduce the weight of the rod still further tapered rounded flutes were cut with a 7/16" ball nose cutter.

The last milling was to remove the remaining unwanted metal around the bolts.

A final bit of blending with needle files followed by some emery cloth and the con rod can be ticked off the list.

See Part one here  part two  part three  part foupart five  part six  part seven  part eighpart nine