change in bearing fit due to change in temperature
change in bearing fit due to change in temperature
(OP)
This is probably basic to you'all but I am just not able to get my brain around it at the moment.
Let's say bearing and shaft are of similar material (similar thermal expansion coefficient) and have 0.001" interference at room temperature. Does the interference change if I heat up both the shaft and bearing to assumed uniform temperature?
What about if shaft and housing have 0.001" clearance... same question.
Thx.
Let's say bearing and shaft are of similar material (similar thermal expansion coefficient) and have 0.001" interference at room temperature. Does the interference change if I heat up both the shaft and bearing to assumed uniform temperature?
What about if shaft and housing have 0.001" clearance... same question.
Thx.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.





RE: change in bearing fit due to change in temperature
Last question should have been:
What about if bearing and housing have 0.001" clearance... same question.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: change in bearing fit due to change in temperature
RE: change in bearing fit due to change in temperature
Now I am trying to understand NTN "Ball and Roller Bearings" Publication 2202/E section 7.2 (Calculation of interference). It states:
"To prevent loosening of the inner ring on steel shafts
due to temperature increases (difference between
bearing temperature and ambient temperature) caused
by bearing rotation, an interference fit must be given.
The required amount of interference can be found by
formula (7.3).
DeltaDT= 0.0015 * d * DT (7.3)
where,
DeltaDT : Required effective interference (for temperature)
mm
DT : Difference between bearing temperature and
ambient temperature °C
d : Bearing bore diameter mm"
So, it seems there are two possibilities:
#1 - are they assuming a differential coefficient of expansion between shaft and bearing materials?
#2 - Or maybe they should have defined DT differently as difference between shaft and bearing shaft temperature? Just trying to make sense out of it.
If I'm remembering right, 0.0015 E-3 / C is the coefficient of expansion for most carbone steel... so seems more likely they are assuming #2 - this coefficient of expansion for both materials and assuming a temperature difference between shaft and bearing?
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: change in bearing fit due to change in temperature
and that the shaft is at ambient temperature.
The heat will eventually transfer to the
shaft but probably never get as high as the
bearing temperature.
RE: change in bearing fit due to change in temperature
Diamondjim is correct on this one, it appears that they are
allowing for differental thermal expansion of the bearing on the shaft ie:- that you haven't got uniform heating.
Therefore you would have to know what the difference in temperature was to calculate the required intereference.
So if the temperature difference was say 4 degrees C
then the expansion of the housing bore d would be:-
DELTADT= .0015*10^-3 * d * 4
which is also in this case is the required minimum intereference.
regards desertfox
RE: change in bearing fit due to change in temperature
http://www.usatolerancerings.com/index.htm
RE: change in bearing fit due to change in temperature
RE: change in bearing fit due to change in temperature
RE: change in bearing fit due to change in temperature
Start with a clearance of 0.001"
increase clearance by a few hundredths of a percent.
Still 0.001"
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: change in bearing fit due to change in temperature