Stupid question about square washers

[MrVander]

This is probably a stupid question but what is the purpose of square washers over round washers on timber?

Do the square washers have to be level against then timber, I.e. top of the washer is level and flat?

Cheers!

 

[Jackrae]

The square washer should be between the round washer and the wood. Its purpose is to spread the load over a larger area and prevent the nut/washer combination from burying itself into the wood.

 

[MrVander]

Round washer, I didn't think another washer would be needed with a big square washer on it.

Just started to think tonight if aswell as spreading the load is there another reason instead of just a very large round washer.

 

[Jackrae]

It all depends on the timber, purpose of the bolt etc as to whether you need load spreaders or not. As to shape, I wouldn't think it matters too much, though the square ones are usually at least 3mm thick whereas round ones are very much less - unless you've found something special.