Machining the Small End

A Con Rod Sandwich

Completing The Small End

A Connecting Rod Sandwich

The most difficult bit when machining the small end of the con rod, is holding it without damaging it.

Hence the Con Rod Sandwich, made from some scrap wood.

Making the recess can be done by milling or a bit of work with a woodworking chisel.

The lower shape doesn't need to be particularly accurate, but the part that holds the shaft should be a reasonable fit, to grip the Con Rod.

Milling the Con Rod Small End

The finished small end slot is 6mm wide.

Rather than us a 6mm round end milling cutter, it might be found easier to use a 4mm cutter and gradually widen the slot each side, judging the spacing by eye.

In my case I roughed out the slots with a 4mm cutter leaving plenty of metal to file to the finished size.

Take small cuts with the mill running at a high speed.

Be wary of the swarf when using a round end end mill, it is particularly sharp, and brass splinter get septic very quickly.

The Rough Milled Con Rod

The alternative way of making the slot in the small end is to drill a hole for the base of the slot then cut down with a junior hacksaw, leaving sufficient metal to clean up the the slot to the required width.

Final filing to shape

The illustrations below show the final shaping of the Connecting Rods and some of the tools used.

The shaping is for decoration only - it is not essential to the running of the engine.

The use of diamond cutting burrs or points can save a lot of time and effort in the initial metal removal and obtaining the shape required.

I am using the diamond point for a lot of different jobs around the workshop, I find that they work better at slower speeds, stat off slow they tweak up the speed and try again until you achieve the optimum for you.

Shot of Workbench During Shaping and Polishing

Showing the difference

Showing the Difference

The Connecting Rod on the right is nearing completion, you can see the markings of the diamond points on the top part of the rod.

The Completed Connecting Rod

One connecting rod ready to be put away until the final assembly