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ENGINEERING

Tolerances

ABEC Tolerances (Figure 1)

The Annular Bearing Engineers’ Committee has established four classes of tolerances for ball bearings, known as ABEC- 1, ABEC-5, ABEC-7, and ABEC-9. The highest number indicates the class with the most exacting tolerances.

Every ball bearing manufactured by The Torrington Company is made to close tolerances, adhering to the established ABEC standards. Even the most liberal classifi- cation of ABEC -1 assures a precision product. Many applications in numerous types of machines can be satisfac- torily operated with ABEC-1 tolerance bearings.

However, for applications involving high speeds, extreme accuracy and rigidity in such equipment as high-grade machine tools, precision wheelheads and workheads, woodworking machines, superchargers, jet engines, sensi- tive precision instruments and digital computers, Torrington manufactures a complete line of superprecision ball bear- ings made to ABEC-9 tolerances.

Basically single row construction, these ball bearings are available in four series, named ultra-light (9300), extra-light (9100), light (200) and medium (300), providing a consider- able range in external dimension relationships.

Before it can be determined which type and classification of Fafnir precision bearing is the best suited for a particular application, all details of the bearing mounting, bearing tolerances and eccentricities as listed in the dimension tables – and cost – must be thoroughly explored. Obviously, it is not economical to attempt the use of low precision bearings on an application where extra-high speeds and ultra-precision bearings are required.

Assuring consistent performance and interchangeability, Fafnir precision bearings are manufactured to close toler- ances. To take full advantage of this precision product, it is expected that equally close tolerances be used in the production of mounting components (housings). Therefore, special consideration must be given to the particular details relating to proper shaft and housing fits and the housing design.

Values of standard tolerances ABEC-7 and ABEC-9, for superprecision ball bearings used in machine tool applica- tions are shown on pages E4 and E5.

In Figure 1, the chart shows the various classes of toler- ances for 35-millimeter bore size, light series bearings (207). To meet the requirements of the machine tool industry, even ABEC-9 tolerances do not represent the ultimate, since some special applications require even higher precision.

Tolerance

Bore

Outside

Inner Ring

Outer Ring

Inner Ring

O.D. Square

Diameter

Diameter

Eccentricity

Eccentricity

Side Runout

with Side

7

9

1

57

9

1

57

9

1

57

9

1

57

9

1

57

9

.0010

.0009

.0008

.0007

.0006

.0005

.0004

.0003

.0002

.0001

ABEC TOLERANCES

35 MM Bore Light Series Bearing

5

ABEC .0000

1

Figure 1 — ABEC Tolerances

102800

E3

ENGINEERING

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