Vintage Workshop
Services for Brough Superior motorcycles and their contemporaries

Castle forks spring abutments last update: 2/2004


I ordered a pair of plungers from the Brough Superior Club, assuming these were ready machined items, but they were castings.

So, well, let's machine them.

First step was to bore the casting. Fortunately the top can be taken in a 3-jaw chuck, which means you can machine the lower part to run true to the top part which will not be machined at all.

Next, with a live centre in the bore made before, the outside can be machined to be a nice fit in the front tubes.

Now the bit is reversed and the bore for the spring guide rod is machined.

Unfortunately the outer diameter cannot be completely finished on the lathe, as the pivot pin is in the way. Thus I finished the top 2 millimetres on the dividing head of the mill.

It had to go on the mill anyway, for making the pivot pin quite rectangular to the main body.

After milling the end plain, I bored the hole for the thread and a centre bore on the opposite side.

After which it could go back on the lathe to turn the outer diameter of the pivot pin.

which was it, save for cleaning up the bit that goes in the slit of the tubes a little, and save for the left and right hand threads in the pivot pins...



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