Vintage Workshop
Services for Brough Superior motorcycles and their contemporaries

Castle forks front leg tubes last update: 1/2004


Well, cleaning up the end and turning the diameters for the thread and end are nothing special, nor is cutting a 1"*26 tpi thread, but it all needs doing.

Cutting the slots for the spring abutments was a bit more demanding, however.

My first attempt (after devising a suitable way of clamping the tube) was to run two successive cuts with a 1/16" slitting blade up the tube. Unfortunately I had to find there is some residual stress in the tube, leading to a slight expansion of the diameter after slitting. Which can be corrected by considerate application of the vice jaws, but this makes the slit a bit too narrow again.

Thus, for a second go, I set up two 1/16" slitting blades at a 1/8" distance. This worked quite fine.

I could have used a 1/4" disc cutter, but I did not like the big cutting area on a thin-walled item. And I did not have one, to be honest...

I made a few more tubes, as I learnt that usually setting up the machine takes much longer than doing the job.

Yes, I have cleaned the swarf out in the meantime....

And I made a few top nuts. In stainless steel, of course.

Drilling the big hole isn't too much fun, but what can you do?

Screw cutting the internal thread on the lathe was a bit exciting, as you don't want to run the tool against the blind end of the bore. But I did not dare to ask how much a 1" * 26tpi plug is...


Ok, that starts looking like a pair of Castle forks.



To be continued.....



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