Making an internal circlip

I am restoring an Autojumble 1950s Burman B52 motorcycle gearbox. The mainshaft runs in 2 ball bearings, located in the diecast aluminium case by a combination of interference fit and a locating internal circlip, one of which is missing. It fits in a 40mm diameter slot, is around 30 thou thick and made from 3/16 deep strip, with a hole at each end for circlip pliers. Modern DIN internal circlips are far too thick and I lack the capability or tools to widen the circlip groove to take modern ones. These circlips are very hard to come by and I am thinking of making my own; suitable spring steel plate is available annealed or tempered. I have made discs and washers from thin plate before, by cutting rough shapes, sandwiching beween offcuts, drilling to fit an arbour, cutting the O/D, then boring to internal size. For a circlip I would then cut out a bit of the circle. My problem is how to get the required degree of outward 'spring' - should I just tweak it out a bit over 40mm by hand prior to tempering or is there a formula? I would oil harden it (the easy bit), but does it need subsequent tempering (much harder to get the right colour) given that once fitted, it is unlikely to be removed again in the next 50 years or so? Thanking you, Andrew

I'd give Cirteq a ring

**LINK**

it's amazing how helpful people can be if you explain what it's for. If they can't help they will know someone who can. making one sounds like a risky business, if it fails it could ruin your lovingly restored gearbox

Also try these people, they seem to have everything known to man for Burman gearboxes

https://www.draganfly.co.uk/index.php/burman-gearboxs/cp-ba

+1.

Wot he said. Just buy one. A correct imperial circlip for a 50's Brit bike gearbox. If Draganfly don't have one (which would surprise me), buy the latest issue of Classic Bike or similar and peruse the ads. Plenty of specialists.

Duncan, thanks very much for this, Draganfly have them at a very reasonable price - I had no luck through AMC supply sources. I no longer need to make my own and this thread can be considered closed. Cheers, Andrew

Andrew, whether you make the circlip or not, it must be tempered after hardening, if you don't it will probably break as you close it to insert it.

Ian S C

Had all else failed, it would have been possible to have the "Thick" metric clip surface ground to correct thickness providing it was done with a flood coolant operation.

Regards Ian.

If your search proves to be in vain, I vote for surface grinding.

Hey Ian ( a.k.a. Circlip ) I was hoping that you would have an answer!

Norman