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/

 

[IRstuff]

Sure, they can; do you want to pay $5/washer?

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[BreadboardPerson]

Thanks.

$5/washer is too expensive. So when I design using CAD, what thickness do you recommend to use?

The ones I am interested in have thickness: 2.3-2.7mm, 2.4-2.7mm, 1.3-1.7mm.

 

[JohnRBaker]

Have you looked at 'Thrust Washers'? Granted, they're not sized like normal flat washers, but they do have a consistent thickness, and you might find one that'll meet your needs.

John R. Baker, P.E. (ret)
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[BreadboardPerson]

Thanks. I just checked. They don't seem to have the size I want. I need something with OD about 22mm and ID about 12.8mm or slightly larger. Ideal thickness is about 1mm or slightly thicker.

https://www.mcmaster.com/thrust-washers/thrust-bearings-6/

 

[3DDave]

What value is used in model depends on what effect one cares about most. Use the thin one if it is used for a strength or deflection analysis, the thickest for weight and minimum depth of thread engagement if used under a bolt or nut. Or create one with an indicator curve on the side to show how thin it can be.

 

[mfgenggear]

order thicker washers and have a shop grind them to the exact thickness needed.
create a drawing of necessary if special washers are needed. not un common.
it's a cheap to have them surface ground all at once

 

[BreadboardPerson]

In the past I used alumimum washers but the Aluminum washers that fit my OD and ID specs have thickness of about 2.3mm. In the case of Metal Sealing Washer, it has thickness 1.3-1.7mm. Haven't used Metal Sealing washers. Are they also as rigid as their aluminum counterparts and have smooth surface? Perhaps stay away from PTFE Plastic washers as they are not as rigid?

 

[mfgenggear]

may be discuss the exact application require for your needs

 

[XL83NL]

Why not use an ISO 7089 washer? An M12 seems to fit your needs quite good, though OD may need some adjustment.
They have +/- 0.2 mm thickness tolerance but i doubt in practice you‘ll experience any negative effects.

Huub

 

[hydtools]

Even if you custom finish the washer, it will have a tolerance batch to batch. Use the mean of the range.

Ted

 

[BreadboardPerson]

Thanks Huub. Do you have the link? I configured ISO 7089 but the thickness are 2.3-2.7mm.

https://www.mcmaster.com/washers/system-of-measurement~metric/od~24millimeters/id~13millimeters/

I use it to fill in the gap in between a servo motor and a bracket that it turns.

 

[mfgenggear]

metallic or non metallic

 

[BreadboardPerson]

Hi mfgenggear, sorry what do you mean by "metallic or non metallic"?

 

[BreadboardPerson]

For my application, which type of washer is recommended?

 

[TheTick]

If you need a washer, buy a washer, if you need shims, get shims. McMaster gots all kindsa shimses.

 

[mfgenggear]

@ BreadboardPerson ok sorry
metallic = stainless, carbon, brass, aluminum
non metallic= plastic all categories
non magnetic= aluminum, brass, copper, 300 series SS, any thing a magnet will not stick to
magnetic= 400 series SS, carbon steel, any thing that a magnet will stick to.

so it appears to me you need a spacer really and not a washer.
and it has to not slip. shimming as the tick said would work too.
but I would prefer a spacer as not to be assembled wrong, remember murphy's law, if can go wrong it will.
if this is a high production assembly apply a part# on the parts list. can't cost that much.
if this is R&D , then washer and shim it.

 

[BreadboardPerson]

Thanks. What is the different between spacer and washer? To me, spacers are those white tall plastic or metallic standoffs. Washers are thinner ones. In terms of materials, among PTEG Plastic, Aluminum and metal Sealing, which is better?

 

[mfgenggear]

washer is generally between a nut and screw, or bolt and threaded part.
a spacer is used in mechanical assembly such as a shaft between
any mechanical device to obtain the correct spacing. and has no visible gap, and has to have a correct spacing.
in your case a motor has to have the correct spacing to a bracket.
thus a spacer.
a washer normally does not have a concern with spacing, as the only concern
is bolt or treaded parts is torqued down and snug. no visible gap.
but both I guess can be interchangeable.

 

[mfgenggear]

what is the torque applied on the bracket by the motor or fit form and function?