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 rollerbecause 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 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 about1 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.