Thrust washer

OK can anyone explain to me in words of one syllable what a thrust washer is?

If you talk about 'axial forces' you will have already lost me lol

A Thrust Washer takes the force along a shaft (The axial force).

In the case of a lathe, it takes the load trying to push the Mandrel out of the back of the Headstock when you are taking a cut along the bed towards the Headstock. If the lathe has Taper Roller Bearings in the Headstock, these not only locate the mandrel radially, but also take the thrust.

Could take the form of a washer, (Bronze, Phosphor Bronze, Brass, Nylon, etc) or a bearing with needle rollers disposed radially, sandwiched between two hardened steel washers. These, in turn bear against a face of the housing.

Your car engine will have thrust washers between faces on the crankshaft and the crankcase, to take the thrust when you depress the clutch pedal.

In a ship, the thrust of the propellor against the hull used to be taken by thrust blocks made of wood, (Lignum Vitae)

Howard

Axial means in line with the axle, and radial means in line with a radius. So, as Howard says, a thrust bearing copes with axial loads or forces or pushes or pulls along the axle, spindle, shaft, etc.

It does seem an odd term when you think that ALL bearings* are intended to resist thrust, why pick on axial ones to pin the name to? But I suppose its the same as electric motor 'brushes' which are solid lumps, and 'analogue' clocks that go round in identical jerks and have hands ...

* PS not compass bearings, though!

Regards, Tim

Edited By Tim Stevens on 05/11/2016 15:52:37

Words with more than one syll-ab-ul folks. Try it like this.

It is the thing used at the place where the force of the cut (for a lathe), or the load on the end, is thwart in the line of the axis of a round bar while it is spun (or it could be still and pushed, I dare say).

The force on a shaft while it turns by a belt drive would be like a spoked line of force which bears on the side of the thing in which it runs (on which the shaft slides). This force must be pushed back by a force of the same size, too.

All force must be the same in all lines or the shaft would move. These two are at right bend to each and each can be more boss at any one time.

Edited By not done it yet on 05/11/2016 16:17:28

I've never seen a ships propeller thrust block in wood but have seen propeller shafts in wood bearings. Normally the loads are carried in thrust block that has a series of pads that have a pivot on them to allow an oil film between them and disc on the shaft.

OK so how does simply putting a washer on a shaft create this counter force? Wont it just slide on the shaft?

It would be made to bear against shoulder on the shaft.

The washer will not create anything - sorry. This is a difficult question to answer, Woolfie, not because the science is hard but because I do not know where you are starting from. If I make assumptions (such as that you know about Newton's Laws of force and motion) then you might struggle if you are not up to speed on the science, but if I really do start from square one, you are likely to consider me a patronising old fart.

Basically, look at a boat propeller, and this turns, providing a force trying to push the boat forwards. This force happens because the propeller is pushing the water backwards. What stops the force back from the water from pushing the propeller shaft into the boat? Well it has to have something to push against. And to stop this thing (whatever it is) from wearing out as the prop shaft pushes against it, we add a device designed to resist the force without wearing out. This 'thing' is called a thrust bearing. It holds the prop shaft in place (up and down and side to side) so the water does not get into the boat, but its main job is to resist the push of the prop shaft.

In practice, a shoulder on the shaft might push against a washer fitted to the boat - this is a very basic thrust bearing. But the turning combined with the continuous force will wear it out, so we try oil and grease - which are an improvement. But the turning action squeezes out the lubricant, and the continuous force does not allow any slack to allow more lube in. So, special self-lubricating material (such as wood or plastic or metal impregnated with oil or graphite, etc) is used, and there still needs to be a smooth flat surface to push against, so this is what the washer provides. Clever thrust bearings can include steel balls or rollers to avoid the sliding, or the use of swivelling plates which tilt under load to allow lubricant in (as mentioned by Bob Brown above).

I hope this helps, but do ask again if there are gaps in the explanation for you.

Regards, Tim

PS: I am reminded of a student who was puzzled by an explanation of how a car engine works. After several frowns, he said 'Does petrol burn, then?'

Can't do it with words of one syllable, but how's this for simple ?

Think of a door 'meeting' a door-stop ...

Now imagine the whole thing spinning

That's a thrust washer In action.

MichaelG.

Hi Wolfie

Have a look at this! **LINK**

else try Wikipedia.

Cheers Michael

M

Edited By stevetee on 05/11/2016 19:54:20

^^^ Concise, but perhaps a little too cryptic, Steve.

MichaelG.

A washer, a circular object with a hole in the centre and usually thin in relation to its diameter. A washer becomes a thrust washer when the thrust or load is placed on its face.

There is a video by EricTheCarGuy on YouTube called thrust bearings and what they do. A thrust washer is a basic type of thrust bearing so this video is relevant to the question. **LINK**

Martin

Thankyou this makes it quite clear. It was the requirement for it to be self lubricating which was the sticking point, I couldn't quite work out what made them any different from any other washer but now I know why!

Edited By Wolfie on 06/11/2016 12:48:21

So in effect, its a sorta flat bearing?

like this...

or this...

or this (much more expensive...)

Always sandwiched between two shoulder/faces/somethings...

Wow. A moderator on a model engineering forum with 500 posts to his name lacks both the basic knowledge of what a thrust washer is - and the ability to Google it. I thought I had a good armchair!

I don't see how that applies to his circumstances. Being a good M.E isn't about belittling those who know less than you might.

Michael W

It sure would help if you let slip a few details about what exact application you are looking to use a thrust washer for.

They don't necessarily need to be lubricated, or even self-lubricated at all. A thrust washer can be used in a totally dry application, for example taking up end float in a shaft where the washer is placed between a shoulder on the shaft and the inner race of a sealed ball bearing.