Washers thickness tolerance 2

[BreadboardPerson]

Hi, I am looking for washers. On McMaster webpage, for each washer they list a range of thickness of about 0.4mm difference. Is it all by luck in getting the thickness I want? Can't they make exact thickness?

When designing mechanical devices that use washers, which thickness value should I use in CAD?

https://www.mcmaster.com/washers/

 

[mfgenggear]

is there a gap between the spacer as to rotate freely or does it have a preload on it, and it does not have to spin?
many simple questions of it's application. you have to be precise for better answers

 

[desertfox]

Hi

Why not just draw up some round steel bar which match the Outer diameter you require and drill a hole through it’s centre matching the bolt diameter you are using and part them off on a lathe to the correct thickness.


“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[MintJulep]

I need something with OD about 22mm and ID about 12.8mm or slightly larger. Ideal thickness is about 1mm or slightly thicker.

All of your stated requirements are "about .... or slightly thicker" yet you are complaining about 0.4 mm manufacturing tolerances.

Do you actually know what you need? If your design can tolerate no variation on a washer thickness then your design is flawed. Because variation will always exist, not only with washers, but with all the other parts in whatever it is that you are designing.

If somehow you really really really need perfect washer thickness every time then buy a big number of washers and measure the thickness of each one and use the ones that are exactly what you need.

 

[BreadboardPerson]

OD and ID can tolerate some variation but for thickness, if there are variations, I need to redesign.

Anyway, the important answer I need to get is: Among PTEG Plastic, Aluminum and metal Sealing, which is better?

 

[MintJulep]

The application matters.

You ask "which is better?"

But you won't tell us for what. So how do you expect a meaningful answer?

A Ferrari 488 is certainly better than a Ford F150. Unless you need to transport a ton of manure.

 

[handleman]

Why do standard washers have such a wide tolerance? Because when used properly by a competent designer for their intended purpose the stated thickness tolerance is perfectly adequate.

If you have an application where you need precision thickness, a different type of component is required.

These can be specified down to ±10µm:

https://us.misumi-ec.com/vona2/deta...WASB&searchFlow=suggest2products&Keyword=WASB

Or, you design your mechanism to allow for adjustment or accommodation of the stated tolerance.

 

[dvd]

Agree with The Tick - McMaster has ring shims.

 

[dgallup]

Or do what we do and lap them down to +/-1 micron.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[mfgenggear]

it's a cheap to have them surface ground all at once

 

[SwinnyGG]

In general, washers have wide tolerances to account for batch-to-batch variation in manufacturing. IF you buy a bag of 100 from McMaster, they are all going to be from the same batch and will be very consistent- in my experience within .1 mm or better.

Buy them 5 months later and you're likely to get the same consistency but a slightly different mean thickness.

So ultimately if what you need is consistency for a single build, you're good. If you're going to be building thousands of whatever you're building over many months, you'll need to explore other avenues.