I'm not keen on having to remove the sump plate to drain the crankcase should this become necessary. I noted an item in the light twins compendium where Martin Jones had drilled and tapped the plate and fitted a 5mm setscrew. I liked the idea but felt that 5mm was too small and that the plate wasn't thick enough to take a decent thread. Not to mention metric threads on a Norton!
So I drilled and tapped my plate 3/8" BSCy and confirmed that there was in fact minimal thickness and so very strong possibility of stripping the thread.
I too a 3/8 nut, coated the bottom edge with JB weld and screwed it down onto the setscrew already screwed into the plate. By tightening it firmly it confirmed that it was in close contact. Afterthe JB weld had set I then applied more around the nut to both add strength and further minimise the chance of leakage.
An overnight test with thin oil and a 1/8" BSP Dowty washer showed that was fine.
I then shortened the setscrew so it just entered the cavity and end bored it to take a 6mm neodymium magnet.
I could of course have paid £40+VAT for a specially made plate, but what is it they say about engineers? Someone who can make for a quid what any fool can make (or buy) for £40?
A more elegant but costlier solution would have been to make an aluminium alloy boss and have it tig welded but it's pretty much out of sight so I'm happy with my solution.
Top view:
Bottom view:
Its since been superseded by another version.