Big end nuts

[simon.holyfield]

Thanks for the advice guys.

The washers are pretty thick, more than a millimetre from memory, certainly more than 12 thou. You can almost see one here:

[Mick D]

Hi Simon

Apologies if I'm reading the photo incorrectly but:

The washer appears to be of too small an OD, it should be at least the same size as the pressure face of the nut, (it looks considerably smaller and risks crushing the alloy bearing cap).

The washer is a lot thicker than I remember mine to be, mine are also a good match to the bearing cap counter bore in OD, (good exercise for the mini lathe, get some oversized thin washers and turn them down).

From my experience in the aircraft industry, the self locking nut would not be considered to be 'in safety', (one and a half threads protruding are needed to achieve this).

I wonder if self locking nuts were ever installed by design, or if they, and the associated undrilled bolts are just an easier option to manufacture / acquire.

If the choice were mine I'd be drilling the bolts, fitting castellated nuts and thin washers to see how the clearance is. You can cross drill with a pillar drill if you fit a plain nut to the bolt and drill through the two together, then you can use the drilled nut as a guide for the other three bolts.

Regards Mick

[simon.holyfield]

The washer is small Mick, but probably not much smaller than the mating surface of the nut (it's chamfered on the mating side). The washer is laser cut and seems quite hard. It's not a cheap stamped component.

I'm fitting a kitchen and contemplating what to do!

[simon.holyfield]

Well... As Roger said, clearance is close but you don't need to remove much material to avoid a clash.

What I've done today is make a 1 mm chamfer on the offending edges of the two timing side nuts, so now I know what clearance I need to provide.

I've ordered a new set of nuts, still self locking but to a slightly shallower pattern (still big end nuts, not something nasty) and I'll use these with larger but thinner washers I think. That will guarantee the self locking bit of the nut is on the full diameter of the bolt thread.

I've not decided what to make the washers from yet.