Bearing Placement Advice 1

[Keratin]

Hi,

I have two sheet metal parts that need to freely rotate alongside each other around a bolt that holds them together.

I'm after some advice on how to achieve this function by adding a ball bearing or a shoulder washer type setup. The load would be very light around 1.5kg.

In particular, how is free rotation achieved between the two sheet metal parts after tightening them together?

Any help would be greatly appreciated. Thanks.

 

[BEMPE16524]

you can read this post:

https://www.eng-tips.com/viewthread.cfm?qid=521802

I showed some examples at the last page.

R.Efendy

 

[TugboatEng]

If they have a bolt that holds them together they won't be able to rotate freely. A pin would be better. How many cycles does this need to tolerate. You may need bushings.

 

[MintJulep]

Load applied where?

Load reacted where?

How much free play in other degrees of freedom can you tolerate?

how is free rotation achieved between the two sheet metal parts after tightening them together?

It isn't. See Tug's suggestion for a pin, and the thread that Bempe referenced.

 

[Doug Hunter]

I agree with the others that more information would help. There are needle roller thrust bearings commercially available which could be placed at each end and in-between the sheets.

 

[mfgenggear]

Based on the information or lack of.
Go with a shoulder bolt, bush each holes, bush between the sheet with oil light bronze or brass. Since preload or lack up on the bolt may want to use a pin instead with a hole and pin it.add washers of course.

 

[mfgenggear]

Or you could preload a bolt if flange were added to the bushing in each hole.
And lock tight in place with minor strength adhesive.

 

[3DDave]

Solid rivet and a hammer works well.

 

[BrianE22]

Do you need to accurately hold the sheet metal pieces together during rotation? If so then you'll probably need at least one bearing. Does the center bolt need preload only to keep the nut from falling off? If so then a shoulder bolt and nut would probably be enough.

 

[Keratin]

Thanks for the great suggestions.

Here's some more info on the design:

- The two metal sheets will need to be accurately held together during rotation without any free play in other degrees of freedom.
- They'll need to rotate slowly in a 90 degree range of motion and there'll be a light load applied around 1.5kg to one of the metal sheets.
- The nut should ideally be fully tightened while still allowing the necessary clearance for movement where the nut does not apply a clamping force to the joint.

I'm thinking something like the image attached which uses a shoulder bolt with step washers but unsure how this design could achieve free rotation while accurately holding the sheet metal pieces together without any other free play.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1724379361/tips/510f440d514f6e24001621b30bf2de8648ea48c0_wrlust.webp[/url]

 

[Doug Hunter]

I think you need to define the maximum allowable play in each degree of freedom, and the dimensional tolerances of the different parts. Zero clearance every time will not be possible due to the thickness tolerances of the different parts. Even if you use conforming parts like tolerance rings or crush washers, it won't be possible to assemble the parts with zero force and zero clearance.

 

[btrueblood]

3DDave has a decent suggestion, but you need to have fairly tight controls on the riveting process if you want the joint to rotate. And/or you incorporate a plastic shim washer to ensure a slip fit after setting the rivet.

PEM has spot-fast pins to do the job I think you are describing, if your materials are within the range of the parts they make.

https://www.pemnet.com/products-ove...fasteners/specialty-fasteners-panel-to-panel/

 

[3DDave]

It's what is used on many car trunk and hood hinges. They may use thin washers as spaces; I haven't wanted to repair one enough to look.

 

[Keratin]

The suggestions are much appreciated. So say I was to go with a bearing for this design - does anyone know what type of bearing may work for this application and have any idea on how to use one in the design? Thanks

 

[Doug Hunter]

Again, one option is needle roller thrust bearings that are commercially available which could be placed at each end and in-between the sheets. The manufacturers literature will direct how to properly employ them.

https://www.mcmaster.com/products/thrust-needle-roller-bearings/

 

[Keratin]

Ok great thanks, will have to look around for one of those needle bearings in 316 stainless as it will need to operate while submerged in seawater.

 

[mfgenggear]

OP
Your kidding right, you could have mention that in the beginning.

 

[mfgenggear]

Op
You're will need to water proof and seal your design.

 

[BEMPE16524]

you need water tight design. even if you use SS316, it does not promise you the protection from any debris.
plus the seawater salinity provides rough contact surface within the bearing elements.
for slow speed, why not use a bush. use proper tolerance and material, it should work perfectly in seawater.
what do you plan to make actually? I mean what sort of machine, equipment, etc?


R.Efendy

 

[Keratin]

Ah ok, yeah thinking the simpler the design the better for underwater usage. The design is basically a sheet metal, mechanical tilting arm for an underwater camera. Thanks