BS4500 (ISO 1101) Fit Question H8/p7

[lancer360]

I have a very good article from the Copper Development Association regarding bronze bearing design. They recommend a press fit of H8/p7. For a 165.1mm (6.5in) nominal bearing OD I have calculated a hole limits of 165.163/165.1 and bearing limits of 165.183/165.143. If you take the smallest bearing diameter and largest hole then you end up with a clearance fit and not a press fit which won't work for a press fit bearing. Did I calculate the limits correctly or is there something not right in the guidelines from CDA?

These values are significantly different than the recommendation from a bearing supply catalog I have.

 

[desertfox]

Hi lancer

The figures for the fit you quote H8/p7 are correct.
What you have though is a transition fit which can either be
a clearence or interference.
What are the other figures you have and is it from the same bearing supplier that your getting your bearing from, if so I would go with those figures.

regards

desertfox

 

[lancer360]

Thanks for checking my numbers. The chart I have from Bunting stops at around 4.5 inches diameter, but I found a different chart from another supplier that shows 0.002 to 0.007 inch force fit for this size bearing. I'm just going to run with that.

 

[desertfox]

Hi lancer360

Is there any temperature involved with the assembly you might need to check stresses or whether you still have a intereference with a rise or fall in temp taking in to account housing material.
I think otherwise you are doing the right thing.

regards

desertfox

 

[lancer360]

I didn't think the temperature range would be much of a problem, but I guess it depends on what you use for a starting temperature when the bearing is machined. Our operating conditions are from -20C (-4F) to 45C (113F) for offshore equipment. If I make an assumption on the high side of 30C for the starting temperature, then I won't lose the press fit until -34C if I use my minimum press fit numbers. The high side won't be an issue since at 30C there is only a 15C temperature increase.

Does this should right?

 

[saty88]

i have a hole with limits 30.006/30.009 and a shaft of 29.990/20.992. I have calculated this as a clearance hole but am stuck as to which tolerance it is equivalent to. PLease can you help

 

[handleman]

1. New question - probably should have been a new thread.

2. Find a table of ISO tolerances and see which one matches yours.