Split Lock Washers

[pcoxe]

Originally Posted By: Merkava_4
Originally Posted By: pcoxe
but what prevents the flat washer from turning and allowing a nut to unwind?


The force of compression. It's supposed to be under a compression load like a spring.


If compression will keep it from turning, why do you need a lock washer?

 

[Olas]

Often times a dab of loctite is just as good at making sure the fixing stays put

 

[Merkava_4]

Originally Posted By: pcoxe
If compression will keep it from turning, why do you need a lock washer?


The bolt is under the opposite force of compression -- it's under tension.

 

[SHOZ]

A split washer does not dig into the surface, like posted above it acts as a spring. Though some lock washers have a textured surface for better hold.

A stat or internal/external lock washer digs into the surface to hold.

 

[Al]

Originally Posted By: SHOZ
A split washer does not dig into the surface, like posted above it acts as a spring. Though some lock washers have a textured surface for better hold.

A stat or internal/external lock washer digs into the surface to hold.

Not saying you are wrong but why is it that these washers are always made in a left hand spiral configuration??

Originally Posted By: SHOZ
You should always place a flat washer with the punched side down too.

Again not saying you are wrong but "why"? Motion between the maring surface is relative..and the mating surface of the machine part and the botton ofj the bolt head are mationg surfaces. I don't see why it matters.

Originally Posted By: pcoxe

If compression will keep it from turning, why do you need a lock washer?

In truth, a properly designed fastener application with the proper amount of torque does not require a lock washer. Its pretty much carry over from the "old days"

 

[SHOZ]

A flat washer is punched out. The downward motion of the punch will leave the top of the washer with slightly tapered sides and cupped surface. The bottom will be square. When placing the washer with the top/tapered/cupped side down it will somewhat act as a spring. It also has the 'rolled' edge to prevent digging into the surface.

 

[Merkava_4]

I always put the smooth side of the flat washer against the machine.
The lock washer or the nut definitely don't need the smooth side.

 

[pcoxe]

Originally Posted By: Merkava_4
Originally Posted By: pcoxe
If compression will keep it from turning, why do you need a lock washer?


The bolt is under the opposite force of compression -- it's under tension.


The shaft of the bolt is under tension, but the underside of the bolt head is under compression from the tension of the bolt shaft.

 

[Cujet]

Piston engine aircraft exhaust systems (yes, they are subject to FAR more stress than automotive exhaust) require lock washers.

Without fresh lock washers on each installation, there is a high risk of the non locking nuts backing off.

The preferred washer is the internally toothed kind.

Interestingly, for the internally toothed lock washer to function properly, the nuts require significant torque. Enough to crush the all of the locking tabs and get them to "bite" into the nut. This is often considerably more torque than the specification. It's a good idea to look at the lock washer and ensure it's fully compressed. Failure to do this will result in the nut backing off after a few heat cycles.

For this reason, many experimental, and aftermarket aircraft exhaust engineers have gone to a single, stainless, split washer. Which crushes much more easily.

In either case, when proper aircraft hardware is used, and proper installation methods are used, removal clearly showcases the locking feature. The nut is difficult to remove and shows marks where the locking feature "dug in".

 

[SHOZ]

What I use on exhaust is a SS bolt, SS lock washer and a grade 8 nut. Do not use a SS nut on a SS bolt on exhaust as they will gall and forever be one. The hardened non SS nut is sacrificial and both it and the SS lock washer are replaced after one use.