oiled bronze bushing clearances

[40fordcoupe]

I have little experience with oiled bronze bushings and I have three questions.

First, for a press fit how much smaller should the hole be than the bearing OD?

Second, should oiled bronze bushings be reamed? I have heard that this closes the pores and defeats the self lubricating properties.

For a light duty application how much clearance is needed between the bearing and the shaft?

Thanks in advance for your help.

[HuFlungDung]

Some of the specifications for the hole depend on the ratio of wall thickness of the part, the bushing and the overall diameter you are working with.

In general, a press fit of .001 to .002 is adequate. This is often 'built in' to the factory size of the Oilite bushing, so that a standard reamed hole (on size ) will be correct. The ID of the bushing might also be oversize by the same amount until installed, when the crush factor may reduce it somewhat.

If it don't fit, you've got to bore it or ream it It is impossible to close the pores on an Oilite bushing because it consists of at least 50% pores and the rest is powder and oil. A bushing will glaze over when run hot and the lubricant gets old, in which case, I would recommend cooking the bushing with a small torch to burn it out. Then, quench it in oil for a recharge. That is just for emergency repairs.

The clearance requirement depends somewhat on the rpm of the shaft. Localized heat expansion while running reduces the clearance and can cause things to seize. On average, you would want a minimum of .001" clearance on the diameter, with an error range up to .002" and this would be as close to perfect as you could get for most applications. If you start with .001" diametral clearance, then you should be nearby the device to check it during run-in when you discover if all the alignments were perfect enough. Rapid heating will tell you that there is a problem.

[40fordcoupe]

Thanks, this is exactly the type of information I need.

I neglected to say that in my application the duty cycle will be very low and I am planning on using schedule 40 black iron pipe for the housing. The static load on the bearing will never exceed 20 pounds. Shaft speed will be less than 200 RPM.
Anyway much thanks,