Normally ,  the shaft is supported by two bearings in radial and axial directions. Then, one of the bearings

is called the fixing-end bearing which carries the load in radial an axial directions.Ie congrols the comparative

axial movement between the shaft andthe bearing. The other one is called the free-end bearing thatonly carries

the  radial load and the bearing can comaratively move inthe axial direction in order to solve the probllems ofexp

ansion of  the shaft caused by changes in temperature and the clearance error in mounting.

    For the fixing-end bearing,it must be chosen from which the axial movent can be prevented.For the free-end

bearing,it must be chosen to use its sliding surface to make axial movement(such be cylindrical roller bearings)

or use its mounting surface to move(such as radial ball bearings).Onthe two bearings,the bearings that onat only

move in the fixed single  axial direction (such as radial thrust ball bearings) are preferable.