Request for advice regarding minimum bushing clearance & material

[John2004]

Hi everyone,

I would like to ask if anyone could please offer some advice on the following...

I have a cantilever mounted round steel housing about 1.5" long that I want to oscillate on a 3/8" OD hardened steel dowel pin. I plan on just pressing a bushing material into the full length of the housing, and then drill & ream the bushing ID to fit over the dowel pin. I need the clearance between the ID of the bushing and the OD of the dowel pin to be as small as possible. I can only lube the bushing once at
assembly and then never again.

I would prefer that the maximum clearance between the dowel pin OD and the bushing ID is not over .001" but I may be able to get away with .002". I would like to use a high pressure grease to lube the bushing and shaft, but how small can my clearance be before it won't allow the grease to go and/or stay between the shaft OD and the bushing ID, or
before the low clearance defeats the lube somehow ?

The housing is just oscillated by hand intermittently. Any
recommendations for a bushing material, bushing ID surface finish, and lube, would be appreciated.

Presently, I have no choice but to press some bushing material into an existing housing, but in the future, would I be better off making the housing itself out of some pre-hardened 4140 and then using the housing itself as the bushing material ? Would this wear much better than a bronze bushing ? Would non-hardened 4140 or non-hardened tool
steel wear better than bronze ?

I would like this thing to last as long as possible before the clearance opens up too far. I also think I need to stay with a bushing and not a rolling element bearing.

Any advice or personal experience with bushing materials, loads, and estimated wear rates would be appreciated.

Thanks
John

 

[unclesyd]

If you continue as stated in you post using grease you will are going to have problems in short order. The grease product will oxidize rather rapidly and gum up the works. I would use an assembly past containing a dry film lubricant or a dry film lubricant that will continue to work for a very long time.

http://www.neelyindustries.com/pdf/77.pdf

Here is one alternate (C-Flex) to facilitate Oscillating motion you might want to explore.

http://www.c-flex.com/companyproducts.pdf

Here are two approaches to the type bushing you are attempting to make. These are standard off the shelf items.
They are easily replaceable.

http://www.rollpin.com/ProductInformation/TensionBushings/index.html

http://www.connexusa.com/HTML/principle.html

 

[John2004]

Thanks Unclesyd,

I will check out the links you gave.

John

 

[hydtools]

Here is another source for steel-backed solid film bushings.

http://www.ggbearings.com/

Ted

 

[Heckler]

Here is another source for steel-backed bushings

http://www.afmusa.com/bushings.composite.asp

The DX versions are lead free and the DU bushings have a small percentage of lead which helps if you're running them dry. These bushing can be sized (peened) after installation to achieve the correct dimension.

Heckler
Sr. Mechanical Engineer
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(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[sbozy25]

You might try contacting Saint Gobain or Oilles with your application. They both make tefflon inpregnated steel backed bushings. If you use one of those, you wouldn't really need to lube your pin.

 

[mmart]

If your loads can handle it, think about oilite sae-841 sintered bronze, its self lubricating due to the trace leads in the composition. it's also fairly strong stuff

 

[stfgrizz]

You might want to look a DU Bushing:

http://www.ggbearings.com/products-detail.asp?MaterialID=1&Group=1

I have used these quite a bit and they have perfomed well.

 

[JsTyLz]

What about bearings??? if not at least for future production.