Norton Model 50 350cc
Part 8
Stainless steering bearing cover produced by spinning
This was yet another one of those jobs which I just fancied tackling. In view of the fact that I had fitted taper roller bearings to the steering head, the top bearing stands a little higher than normal so the dust shield needs to be a little deeper to make it look right and cover the gap. It's a while since I attempted any spinning work, especially in stainless, so I elected to use the process for this component. True, it could be turned from the solid, which is a waste of a lot of material.
The blank disc was cut from a piece of scrap 1.6mm stainless using a thin cutting off disc in the angle grinder and it's surprising how accurate this method can be with a little patience. The disc was then mounted in the grooves in the 4 jaw and centred from the original pop-mark left from marking out. This was then drilled and bored to suit the stem nut spigot.
I made a former from a large lump of scrap mild steel with dimensions to suit the INSIDE of the finished part, then with a blank disc centred and mounted against this, all that was then needed was a trapping block held in place with a heavy duty revolving tailstock centre. In the past I have used a piece of hardwood mounted in the tool post as a 'pusher' to persuade the material to conform to the pre-made former, but this time a piece of scrap Dural bar was used. With occasional lubrication it is not difficult to 'persuade' the metal to follow the former.
I put a generous radius on the bar end to prevent a rapid change in angle which might be a stress raiser.
The edge which has been wrapped around the former needed just a tickle from a parting tool to clean everything up and get the depth right before final polishing.
The trapping block was in fact an old fan spacer from an early Mini! ('Nivver throw nowt out, tha nivver knows when it'll come in 'andy for summat')
The finished article ready for fitting
I think it looks neater this way, with the bare minimum of clearance between it and the headstock