When to use a washer?

[Woodworks]

This is one of those little things in life that puzzles me so can someone enlighten me?

 

When putting bolts in wood I understand why a washer is used. It spreads the load and avoids the hex of the nut or bolt cutting into the wood as it is rotated. Now on thin steel I suppose a washer may spread the load but on thick steel it seems unnecessary. Working on the processor a couple of days ago and notice they have used a washer under just the bolt but not the nut

[Breezeblock]

i always try to get a good quality washer under both sides if its going to a high torque i try and get hardened washers or verbs washers ,cat do good quality fasteners so do peiner

[GardenKit]

The purpose of a washer is to spread the load on the parent material so that it supports the load of the bolt head.

 

So a bolt holding a cast iron gearbox to an engine does not need a washer, whereas a bolt holding an aluminium one might.

 

The tendancy is to use flanged bolts and nuts on aluminium rather than washers. The Verbus flanged bolts also have little teeth under the flange which helps to prevent loosening.

[scraggs]

If the bolt is too short then no washers

If it is too long use a washer

If it's still too long use a washer either side.

And if it's still too long use one either side with a spring washer.

Simples

[Woodworks]

The purpose of a washer is to spread the load on the parent material so that it supports the load of the bolt head.

 

So a bolt holding a cast iron gearbox to an engine does not need a washer, whereas a bolt holding an aluminium one might.

 

The tendancy is to use flanged bolts and nuts on aluminium rather than washers. The Verbus flanged bolts also have little teeth under the flange which helps to prevent loosening.

 

So 3mm steel to 3mm steel needs no washers?

[Woodworks]

If the bolt is too short then no washers

If it is too long use a washer

If it's still too long use a washer either side.

And if it's still too long use one either side with a spring washer.

Simples

 

This fits with what I find on our various machines

[C.J]

Probably just cosmetic - to stop nut/bolthead or spanner/socket damaging paintwork during assembly.

[aspenarb]

I am going to show my age now:blushing: Going back in time when men were men and pansy`s were flowers hex blots and nuts were made from hex bar. No chamfers were put on either and washers were needed to stop the work piece getting gnarled up when tightening bolts or nuts. If you look at any modern bolt or nut you will see they are made with the radius on the edge forming its own washer so that for conventional bolting up of metal parts there is no need for an extra washer. Obviously spreading the load with washers is necessary on some apps like plastic mudguards and ali but for general steel fabs its not.

 

Bob

http://arbtalk.co.uk/forum/attachment.php?attachmentid=164499&stc=1&d=1409909152

Edited September 5, 2014 by aspenarb

[peatff]

I'm going to be controversial here and say the illustrated item is a machine screw being used as a bolt as it is threaded all the way up. Some applications state that washers should not be used like cylinder head bolts as they can alter torque readings but for non critical applications some say put the washer under the part that turns to prevent damage to the surface.. If I can find the washer I put it in and if I have lost it I leave it out

[Stubby]

When you are really grubby .......