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Recommendation for metal sleeve bushing material for pivoting motion 1

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John2004

Mechanical
Mar 29, 2004
237
Hello everyone,

I am hoping someone can help me find a suitable bushing material for a product I am developing. I am having a heck of a time finding something that looks like it will wear well and be reliable.

I need a plain sleeve bushing that will be self lubricating and provide good life in a slow moving, intermittently oscillating application, where the bushing rocks back and forth very slowly and intermittently.

The bushing ID is 1/8" and the bushing OD is 3/8". I am using the bushing as a small cam-follower roller. The cam is rotated by hand via a small lever, so the motion is very slow and intermittent. However, the loads are fairly high for such a small bushing, and with the oscillating movement, and the fact that the bushing cannot be lubricated, I am worried about wear. I want the product to be maintenance free and provide years of service.

The maximum load on the bushing will be 7,168 PSI, plus I guess I should have some type of safety factor. The average sweep angle will be about 9 degrees, at an average speed of about 1 to 3 Hz. I think the average surface speed would be 0.2 to a maximum of 0.4 FPM. The device will always be operated at room temperature, and be in a very clean household environment with no dust or dirt. There is also no chemical exposure. The bushing will rotate on a hardened dowel pin meeting ASME B18.8.2 standards, I can either use plain ground finish, or black oxide finish. I could also go with a 303 stainless shaft if needed. In this application as a cam-follower, the bushing rotates on a stationary shaft. I could put a small amount of lube on the bushing at assembly, but never again after that point.

The motion will always last for only a few seconds and then stop. It may last 1-3 seconds on average, say two or three times per minute, and then the rest the time the device is at a standstill, with a static load on the bushing, of about 4,266 PSI, which could also be considered the “average” bushing load, but the maximum will be 7,168 PSI. The load changes as the cam is rotated. It might be used intermittently, for about 36 minutes total per day, ( i.e., 36 minutes of intermittent start / stop use, over the course of around 3 hours, each day).

I won’t need much running clearance, since the device always operates at room temperature, and since heat from friction will not be enough to cause any significant dimensional changes to the bushing, the speeds are too slow and intermittent. However, I would like to keep the maximum clearance between the bushing ID and the shaft at .004” or less. So, if I start out at a clearance of .003”, this only gives me .001” for wear. Maybe I could get away with .002” of wear for a maximum clearance of .005”, but I am not sure. Ideally, I need something that can provide years of service, with very low wear rates.

I tried some plastic bushings from but found that they were so slippery, that there was sliding between the cam and the bushing OD. This caused the cam to wear a flat spot on the bushing OD. I then tried the "FB" series bushings from but since they are a wrapped or spit bushing, it seems when the bushing seam lines up with the cam, the cam spreads the bushing apart at the seam.

I thought of pressing the above mentioned bushings into a steel tube, to solve the aforementioned problems, but then the bushing OD becomes about 1/4". I am working in such a confined space, that I cannot really make the cam any smaller at all, because the minimum radius of curvature becomes to small. Therefore, I really need to stay with a bushing that has a 3/16" OD.

I also thought of putting some “belt dressing” on the plastic bushing OD, to insure that the friction between the cam and roller OD is always greater than the friction between the roller ID & shaft, in order to eliminate sliding between the cam and bushing OD, but I just don’t know how long it would last, and I need the product to be maintenance free.

Since the plastic bushings seem to be to slippery on the OD, and I cannot press them into a metal tube to make the OD less slippery, since the OD will then be too big, I figure I must need some type of metal roller.

I have not been able to find a stock bushing that meets the requirements, so I am hoping someone can recommend a bushing material I can machine or fabricate the bushings from.

I would really appreciate any advice anyone can offer.

Thanks for your help.

John
 
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John2004
you might want to contact maritex%upnaway.com
Substitute % with @
They should be able to assist.
 
Hi everyone,

Correction to my previous message:

The bushing OD is only 3/16", not 3/8".

That's one reason I had such a hard time finding a stock bushing.

John
 
Hello everyone,

I am thinking of trying to use some 3/16" OD drill rod from for this roller. It's held to close OD tolerance, and I can just cut to length and drill the center hole out.

Would drill rod provide both the needed load capacity and decent wear resistance ? Perhaps I can shoot for .001" or .002" running clearance, and then that will leave at least .002" for wear. Do you think I could get a decent service life ?

I will be using a standard 1/8" OD hardened dowel pin as the bushing shaft.

I can get the drill rod in A2, D2, M-2, 0-1, S-7,or W-1. Which grade would be best ? I am thinking of using W-1.

What type of lube would you recommend ? I can only lube once at assembly, and then never again. I guess the ideal lube would be a high pressure lube that is good for pivoting motion, and that will stay in place, and last. I also have to be careful not to get any on the bushing OD.

Lastly, would this be just about as quiet as a standard bronze bushing ?

Please let me know what you guys think, I would appreciate any advice or comments from anyone. Perhaps someone at the forum has had experience with a steel bushing oscillating on a hardened shaft.

Thanks again for your help.

Sincerely,
John
 
There is a company in Vancouver Washington called EDT Bearing that can help you. They specialize in supply of polymer bearings for special applications. I have used them for several years and they have always been able to provide a solution. Good Luck
 
Suggestion
The cam follower could be made out of a material called DEVA which is very simliar to OILITE only harder.
These are UK trade names - they are on the web.
Oilite is available as rod & tube so it can be made into whatever shape you need, this may be too soft.
I have only ever had DEVA as made up bushes - I have used them in small mechansims to good effect.

They both have graphite sintered into the material they give the boundary film lube you need, the one thing you must not do is ream the bores in these materials as it closes up the lube pores, if the spindle is tight on assemble you can generally force some same sixe material in & "work" the bearing looser.
 
Hi everyone,

Correction:

The average sweep angle for the bushing is 42.25 degrees, not 9, and the average surface speed would be around 0.46 to 1.4 FPM. I got my figures mixed up. Everything else in the post is correct.

The device will probably have an average "turn on" time of 3 seconds, and an average rest period of 27 seconds. If it's activated an average of 3 times per minute it will be used for 9 minutes total per hour, for 3 hours per day. If I can get 1,642 hours of life, the product will last 10 years.

Thanks for your replies, I will check into all of the suggestions given. I would appreciate any other feedback anyone might have.

It seems there must be some cost effective material out there that will work well in this application.

Is making the bushing from drill-rod viable ? The problem is, I can only lube this thing once at assembly, and then never again. Even lubing it once at assembly will be difficult, and I have to be very careful not to get any lube on the bushing OD. All the parts are so small, and everything is a tight fit.

I don't really have any way to quickly simulate years of use in a test, to find my answers that way.

Thanks for your help.
John
 
John,
INA has a line of bushings that would probably work for your application. Don't know if they have inch sizes but should have something in metric. Look for ELGES and Permaglide in the products section.

Mike
 
I don't see how you are going to get a bushing with a 0.031 wall thickness if there is any length.

I don't think you will be able to drill a 3/32 rod to your dimensions on a consistent basis. You might EDM it if again it's not too long.

What is the length of the bushing?

What is the material that the bushing going to be put into?
 
Hi everyone,

Thanks for your suggestions so far,

In response to your questions Unclesyd,the bushing length is 3/16", just like the OD.

The bushing is not "put into" anything, it just oscillates on a shaft, in response to a cam curve being in contact with it. It's a cam-follower roller. The cam is made from 4140 steel hardened to Rockwell RC29 to RC32 or so. The cam is also 3/16" thick.

Thanks,
John
 
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