Hi All,
Japanese Engine manufacturers use a lot of Bolts with a Captured spring washer no flat washer as well.
One thing to remember make sure that the nut you are using no mater what type is the same Tensile as the stud or bolt.
Regarding flat washers using Hardend ones means that what ever Torque is applied it will not compress as will a standard mild steel one will resulting in a lose fitting.
The comment on nuts one that does cause problems is the NYLOCK the lock part works fine but the nut part as standard off the shelf is not HT so if using on HT bolts or studs make sure that the NYLOCK nut is HT.
some thing to think about

As far as I know the original 'spring washers' were just that, wider section and without aggressive end tangs. Not sure if this style is readily available now.
The newer tang type, apart from being too narrow, make a mess of the nut and base metal when unscrewing and are to be avoided.
For originality I try to re-use original washers still with a little spring. I think that with proper tightening and regular checking these are OK.
The most unusual spring washer is the Lucas double spring used on the switchboards - don't drop them!
The cylinder head nuts were fitted with plain washers, as were the manifold nuts.
The List of Spare Parts show which assembly has a plain washer, spring washer or lock washer.
I think that parts assembled with a spring washer and a plain washer look fussy and wrong.

Tony.

Many moons ago I bought the remains of a 1925 Chummy (Longbridge body) which had been badly damaged in a fire - allegedly shortly after it had been delivered new. The lack of wear in the gearbox & most other mechanicals (although the crankcase itself was melted) supported the rarely-used story. So let's take just the flitch plates, or valances as many call them :- the rear flange that bolted to the footboard at 45 degrees had no supporting angle-piece as on later models & the holes to the footboard were 1/4". On the side (@ rear) bolted to the lip on the mudguard were two 3/16" screw-head bolts & nuts, each bolt with 5/8" diam. flat washers under the head, NOT under the nut. (Nut to inside of valance, head against guard-lip). Along valance to bottom edge of guard = three off 3/16" screw-head bolts, nuts & washers again as above. At the front top corner where mounted to the guard support strut, was a 5/16" bolt & nut with (1 1/4" diam.) mudguard washers under each. Not a sign of a spring washer anywhere, and I've selected an area where it's highly doubtful that the panels would have been disturbed. So when, if at all, did Sevens - at least on the panels - start using spring washers? Is the common use of hexagon-head bolts, large-diameter mudguard washers, spring washers everywhere really original? Cheers, Bill in Oz

Location: Victoria, AUS.

I must be missing something here as I cannot see what a split spring washer does.
It requires very little load to flatten one so by the time the spring action comes into play the joint is loose and whatever is going to break or fall off will. I also agree with Bob that all they do is fxxk up your torque settings which if set correctly will stop the bolt or nut coming undone in the first place. So can someone put me straight?

Location: London