THE LATHE - 4

A Lanchester Nut

No, not me, but a component for my classic car.

We're talking wheel nuts here, manufacture rather than purchase, and therefore more appropriately discussed in this section, than in my 'Lanchester' pages.

You might expect that any car wheel nuts would fit any of the wheel studs to which the four road wheels are attached, but there are exceptions - including my 1935 Lanchester.

 In this case, and presumably with other Lanchesters of this vintage, the nuts for the wheels on the right (looking from the rear of the car) are marked 'R' while the nuts for the lefthand wheels are marked 'L'.

Fanciful, you may say, but these markings have a deeper meaning in that the actual nuts (and bolts/studs) were made with right and left-handed screw threads respectively.

My particular problem was that the hexagon of one of my 'L' nuts was well worn, making it difficult to tighten firmly onto the stud, and these nuts seemed to be as rare as hens teeth - so I decided to make a new one.

Just to make things a little more interesting, there was no 'Workshop Manual' printed for my model - although even if there were, it would perhaps have been a bit much to expect details to include screw thread sizes!

Identifying the nominal bolt diameter and correct thread size was not as clear cut as I had thought, even with micrometer, vernier gauge and a set of thread gauges, but eventually I decided sizes on the basis that surely a pre-war British car would employ Imperial rather than Metric measurements. (More on this later).

The next step was to order metal and tools - a 12 inch length of one inch diameter stainless steel bar, two tools for cutting the required internal thread, and two end mills for forming the nut hexagons.

You will note that I ordered spare tools - just in case!!

While awaiting delivery of these items I turned my attention to the workings of the lathe, as there was no facility on my model for altering direction of chuck and leadscrew independently of each-other. (Unless I just couldn't find it).

The switch on the lathe altered both at the same time, and while the directions in which they moved were correct for cutting right-hand screw threads, I would need to start off with one of them reversed, to cut left-hand threads.

The answer was to insert another cog into the gear-train driving the leadscrew, (having first set up the correct gearwheels to obtain the required screw thread), and after some experimentation I ended up with the arrangement shown opposite.

'Production' could now commence, but before 'turning the page' I would refer back to the top picture, in order to point out that there was a further hazard with these nuts - they each have a 'built-in washer' - which is why a round metal bar was needed, and not a straight forward hexagon shaped bar of appropriate size.

You may note also that the nuts have a 'blind' end, making the  required drilling and screw cutting more interesting.

Oh joy!!