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# Bearing effective interference

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## Bearing effective interference

(OP)
Hello,
do anyone have an idea about :
how to calculate value of bearing effective interference ?
what is the difference between bearing internal clearance and effective interference ?

Thanks,

### RE: Bearing effective interference

(OP)
Thanks Tmoose

I've seen NSK cataloge before , im already using their equations however , when i tired to get value of effective interference i got a negative value ,which is not acceptable for my calculations i need a positive value...please correct me if im wrong...effective interference = red. in interference due to used fit -(red. in interference due to acting load + red. due to temperature change + red. due to surface finish ) ?

alos, i do have 2 more questions concerning calculation of red. in interfernce due to temperature change :

1- in the attached photo ,the mentioned term for linear expansion coefficient ,was omitted in the final simplified form of the equation , the final used equation was 0.0015 . ΔT . d...where did the value of α been substituted ?

2- when calculating value of effective interference between housing and bearing outer ring, shall i use red. in interference equation = (α1-α2).ΔT. De or (α1-α2).ΔT.D?
Where De is mean outer race way diameter , D is outer ring diameter.

Thanks again for your help

### RE: Bearing effective interference

What is "happening" at installation ? Which ring(s) are interference fit, etc?

What do you reckon is the ΔT of your inner ring/shaft in operation?

What do you reckon is the ΔT of your outer ring/housing in operation?

### RE: Bearing effective interference

(OP)
"What is "happening" at installation ? Which ring(s) are interference fit, etc?"
• I haven't started installing bearing yet......right now I'm calculating value of force needed to pull out / press bearing from its location , which depends on value of effective interference.
• type of used fit between shaft and inner ring : interference fit. while, that between housing and bearing outer ring : transition fit
"What do you reckon is the ΔT of your inner ring/shaft in operation?"
• ΔT is the difference in temperature between shaft and bearing inner ring during inner ring/ shaft operation (10° C)
"What do you reckon is the ΔT of your outer ring/housing in operation?"
• ΔT is the difference in temperature between housing and bearing outer ring during outer ring / housing operation (10° C)

### RE: Bearing effective interference

In the ΔTs mentioned, you need to know what is hotter, and what is cooler.

A hotter housing tends to reduce the effective interference.
A cooler housing tends to increase ( tighten ) it. To the point playing a cooling fan on a hot bearing housing to cool it off can result in excessive interference and possibly dangerously reduced internal clearance.

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