Monday, 15 July 2019

CX500 - Indicator Stems on the Mini-Lathe

Updated: First published 24th June 2019

The latest family acquisition is this 1978 Honda CX500, bought from eBay by son Thomas, and a very fine machine it is too.

The previous owner was, like me, quite short and had lowered the seat producing a very strange riding position; Tom has fixed that now with a new foam and cover.

You can see from the previous pictures that the bike is missing it's grab rail, which includes the proper mounts for the rear indicators and the tail piece. It's absence means the tail piece wobbles and the indicators don't earth properly.

So, a new grab rail appears from eBay but we need some indicator mounts. The ones fitted to the grab rail are wrecked:

We'll make some new ones from a stick of 19 mm grade 303 stainless round bar I have knocking about. We'll start with the end with the bolt recess:

I've drilled this part way through, 6 mm, for the indicator cable.

Then we'll swap it end for end in the collet chuck and machine the smaller diameter, which fits in two top-hat rubbers in the grab rail. We'll need a 10 mm diameter for the thread retaining the stem into the grab rail:

We'll thread these in the tailstock dieholder:

The tubes that carry the indicator stems have a small tongue, to stop the stem turning. The stem has a slot to receive that tongue which we can mill out:

That's two done, ready for the splines:

We'll cut 45 splines to match the original, using a tool ground at 80 degrees and taking 5 thou cuts to a depth of 15 thou. Here's the setup, using the indexing attachment I made; the lathe is used like a shaping tool in this configuration. The machine is out of gear and the E-Stop is locked off.

Here's a close-up of a few splines, cut to depth:

Here are the two stems, with splines complete and polished up with some 240 grit emery.

Next job was to turn up some isolation bushes in black acetal:

And here's the first one fitted to the grab rail:

And with an indicator test fitted:


  1. what are the splines for as they do not match original Honda indicators

    1. Have a look at the original stem in the pictures. These indicator lamps have internal splines...