Request for material recommendation for small 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
John2005
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Goo day John,
You might want to try using oil hardening drill rod, such as O1, O2 or O6. These are readily available from any good tool steel distributor, and machine fairly well for the tool steel family; particularly the O 6, which has a graphitic component.
Heat treatment is not difficult, typically hardening or austenitizing ~ 1450F, followed by oil quenching. Tempering around 400 F should leave you with a hardness range of 62 / 64 HRC.
Regards,
Greg
Reply to
Greg Dexter
Hi Greg,
Thanks for your reply.
Does all 0-6 tool steel have a self lubricating graphitic component, or do I need to get a special type ? I may need to make a small part (not the aforementioned bushing) out of a tool steel that acts as a good bushing material. However, the walls are so thin on the part, I don't think I will be able to harden it.
The part will directly receive hardened dowel pin, that acts as a slow oscillating shaft. I can put a little oil or grease on the shaft at assembly. Since the device is activated by hand, for 1-3 seconds at a time, once or twice per minute, over the course of one or two hours per day, I am hoping I can get decent wear.
However, the loads are high, i.e., 50 pounds average (80% of the time), and up to 100 pounds maximum intermittently. The shaft is only about 1/8" in diameter. This will load the tool steel to 1,818 PSI for 80% of the time, and up to a maximum of 3,636 PSI intermittently. I don't have the space for an actual bushing, so the shaft needs to turn right in the tool steel.
The part will be cnc machined. Please let me know what tool steel or material you think would be best.
Thanks again for your help, John
Reply to
John2005

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