assembly after the stopper 13 is attached thereto in this manner the dynamic pressure bearing spindle motor 200 can be assembled in a built in system with reference to fig4 a dynamic pressure bearing spindle motor 300 in a third example according to the present invention will be described fig4 is a cross sectional view of the dynamic pressure bearing spindle motor 300 identical elements as those in the first example will bear identical reference numerals therewith and the descriptions thereof will be omitted the spindle motor 300 has basically the same structure as that of the spindle motor 100 in the first example except for the following points as is shown in fig4 the spindle motor 300 includes a housing 15 formed integrally with the chassis 10 of the disk driving apparatus and a thrust bearing which includes the thrust plate 5 and a pivot bearing 16 since the housing 15 is integral with the chassis 10 the stator cores 7 can be fixed to the chassis 10 and as in the first and the second example are separated from the motor sub assembly accordingly 3 even in the case where the housing 15 is integral with the chassis 10 as in this example the design of the motor sub assembly is not bound by the shape of the chassis 10 in other words the motor sub assembly of the same design can be used for various shapes of chassis 10 with reference to fig5 and 6 a dynamic pressure bearing spindle motor 400 in a fourth example according to the present invention will be described fig5 is a cross sectional view of.