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Request for material recommendation for plain sleeve bushing

Hi Everyone,

I need to make a small .1875" OD X .125" ID X .1875" long, plain sleeve bushing. I will be using the bushing as a small cam-follower roller. The bushing will oscillate or pivot on a hardened steel dowel pin (RC60) having a surface finish of 8 micro-inch or better.

I found that I cannot use a plastic roller

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because the plastic is so slippery that there is sliding between the cam curve and the bushing OD. This wears a flat spot on the bushing OD. I cannot use a split or wrapped bushing, ( FB series
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since the bushing seam makes a noise when it rolls on the cam curve. The cam curve also spreads the bushing apart when the seam lines up with the cam.

The average load on the bushing (90% of time) is about 100 pounds (4,266 PSI), but it will intermittently have a maximum load of 168 pounds (7,160 PSI). I can only lubricate the bushing ID once at assembly (even this is difficult) , and then never again. I also have to be careful not to get any lube on the bushing OD.

The cam is oscillated manually by hand via a small lever. The cam follower roller has a pivot sweep angle of 42.25 degrees (42.25 degrees in one direction, then back to the start point = 1 cycle). The bushing oscillation or pivot cycle speed is about 1 cycle per second on average but can go to 3 cycles per second. This translates to a bushing sliding speed of about 0.46 FPM to 1.4 FPM. The device is only activated about

1 to 3 seconds at a time, once or twice per minute, over the course of about 1 or 2 Hours per day. The rest of the time the device is stopped with a static load on the bushing of 100 pounds.

The bearing engineers tell me I should not use an oil impregnated bronze bushing because this type of bushing generally does not do well in slow, heavy load, oscillating or pivotal motion applications. This is because heat from rotational friction is needed to draw the oil out of the bushing wall and into the space between the bushing ID and shaft OD.

I have decided that making the roller from 3/16" OD drill-rod may be the most viable option.

I would love to get some feedback from anyone who has had some "real world" experience using drill rod as a roller and/or bushing,. I am interested in what type of loads, speeds, motion, lube, and wear rates were experienced. Also, what grade of drill rod did you use & how hard did you make it ? I hear A2 wears fairly well, and D2 wears even better, but I don't know how hard these two steels are to machine and/or harden. My machinist recommended W-1.

Any bushing experence with pivotal motion, you can share with me, may be a big help.

I can only tolerate about .005" of wear off of the thickness of the bushing wall over the life of the product, so I need something that wears well, but I need the material to be reasonably easy to machine and harden.

I would appreciate any feedback, comments, suggestions, experiences, or advice, from anyone.

Thank you very much for your help.

Sincerely, John

Reply to
johnjmechanical
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Sounds to me like you need a roller made from the drill rod and the bushing made from something else. UHMW poly or the like for the bushing would be my first guess but you do need to research it since the load might be a little high with such a small axle.

Wayne Cook Shamrock, TX

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Reply to
Wayne Cook

Hi Wayne,

Thanks for your reply.

Would the drill rod roller by itself (with no liner on the ID) not wear OK for a slow moving hand operated device ?

The part is so small, the bushing wall is only 1/32" thick, and that is without any type of liner on the ID, that's just making the bushing out of solid drill rod. It seems machining or making a thin walled liner to go on the ID will be very difficult.

The bushing OD cannot be any larger than 3/16".

Thanks John

Reply to
John2005

With a 1/32" wall the bearing is going to deform and you're not going to see uniform pressure on the entire bearing area. In other words, the max pressure is going to much higher than you've calculated. I'd be willing to bet that the pressure distribution between the pin and follower will be closer to that you'd see between the pin and cam if the follower were not present. The formulae for calculating the pressure between two curved surfaces account for the deformation of the two bodies in the contact area.

Googling- bearing "hertzian stresses"

-turned this up among plenty of other promising links.

http://212.90.7.34/shigley/studenti/tutorial/6177-4_Hertz_Contact_Stresses.pdf Do you have to use a rolling follower? Depending on the shape of the cam, you might do better with a sliding follower that spreads the load over a larger area.

Ned Simmons

Reply to
Ned Simmons

John, Have a look at this nickel based, high heat resistent alloy made by Haynes International. It's called HASTELLOY=AE S alloy. You can see it at this Haynes Web site:

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Haynes makes exotic alloys & was originaly founded by a man names Elwood Haynes who was the inventor of the following:

1=2E) Stainless Steel.

2=2E) The 1st internal combustion powered car.

3=2E) slot car racing.

4=2E) An alloy called stellite.

I only know all this because he hailed from my home town of Kokomo, Indiana which is where Haynes still manufactures many of it's alloys today. Hope this helped...

-Wayne-

Reply to
clutchglass

Hi everyone,

Thanks for your replies. I will check into the Haynes site Wayne. If the founder of Haynes invented stainless steel, I am a fan of His.

Ned, I may be able to use a "non rotating" 3/16" OD hardened steel dowel pin for a follower, If this is what you meant by "sliding follower". Would I probably need to put a hard chrome plating on the pin ?

The main problem I would be worried about with a non-rotating pin as a follower is that I think the sliding noise may be too great. I need to keep the device as quiet as possible. I want the product to be maintenance free, and I could only lube it once at assembly. I had planned on making the cam from 4140 steel, hardened to 20 to 32 RC.

If there is a way to make it quiet for the life of the product, and wear well, a non-rotating pin may be the way to go. I found a chrome plating

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that looks interesting, if it can be cost effective.

Thanks John

Reply to
John2005

Hi everyone,

Thanks for your replies. I will check into the Haynes site Wayne. If the founder of Haynes invented stainless steel, I am a fan of His.

Ned, I may be able to use a "non rotating" 3/16" OD hardened steel dowel pin for a follower, If this is what you meant by "sliding follower". Would I probably need to put a hard chrome plating on the pin ?

The main problem I would be worried about with a non-rotating pin as a follower is that I think the sliding noise may be too great. I need to keep the device as quiet as possible. I want the product to be maintenance free, and I could only lube it once at assembly. I had planned on making the cam from 4140 steel, hardened to 20 to 32 RC.

If there is a way to make it quiet for the life of the product, and wear well, a non-rotating pin may be the way to go. I found a chrome plating

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that looks interesting, if it can be cost effective.

Thanks John

Reply to
John2005

Sort of, but I was also suggesting that you try to increase the contact area between the cam and follower. I don't know what the shape of your cam is, but the ideal situation would be if the cam were an eccentric circle, the follower could have a concave face that approximates the curvature of the cam. This would reduce the contact pressure drastically. If the cam is more complex, which I expect is the case, the shape of the follower would have to be a compromise.

A carbide pin would probably be cheaper, unless you're talking about large quantities, and assuming impact isn't a problem.

Ned Simmons

Reply to
Ned Simmons

Ok. For some reason I was thinking that your roller was larger than it is (must of been to much info in that post. :-).

In light of this info then I'd say the best possibility is to use a hardened steel roller. In other words you need to harden the drill rod bushing to the "glass hard" stage. Steel on steel is a terrible bearing surface and tends to gall unless lubricated constantly. However hardened steel on hardened steel is used in back hoes and other earth moving machinery which has to be one of the least desirable environments for plain bearings imaginable. I'd say that it's the best bet you have within your design constraints. Personally I'd prefer some more flexibility in the design but if that's what you've got to work with then that's what you've got to deal with.

There's several things wrong with the design as is IMHO. One is the small difference in size between the OD and the ID. The more difference the more likely the bushing will turn instead of slide. The other is putting that much force in such a small shaft and width. The larger the bearing surface the better it will hold up. Shaft diameter and width combine to make a larger bearing surface. Last is lack of lubrication. If the piece can't be lubricated then you need a self lubricating material. The most reliable seem to be plastic based now days. However with the high load per surface area you have I'd say that you've gone beyond plastics reliable long term load. These constraints are forcing you into a corner which I believe will not have a good long term fix.

Wayne Cook Shamrock, TX

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Reply to
Wayne Cook

Personally, I'd use 52100. I'd rough the rollers, heat treat them to, say,

58/60Rc, then hone and grind them.

Harold

Reply to
Harold and Susan Vordos

Instead of a bushing pivoting on a stationary pin, could you have a .1875 pin that pivots in outboard supports? E.g., ball bearings. Or a pin whose outboard diameter is larger to lessen the psi load? Bob

Reply to
Bob Engelhardt

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