PowerGrip® GT® Belt Drives

Synchronous Belt Drives – Sprocket Specifications
Sprocket Specifications — continued
B. General Tolerances
Gates sprockets are precision made to close
tolerances for the best possible performance.
Sprockets and bar stock included in this catalog are
intended to be used primarily for prototype work.
Gates can supply made to order sprockets in a wide
range of materials (see Catalog number 19994-B).
Gates Application Engineering is able to assist in
sprocket design. General tolerances are included in
the following tables to assist the designer.
Table 19 – Sprocket O.D. Tolerances
Sprocket O.D. Sprocket OD. Tolerances
(in) (mm) (in) (mm)
Up to 1,000 25.4 +.002–.000 +.05–.00
Over 1,000 25.4 +.003–.000 +.08–.00
To 2,000 50.8
Over 2,000 50.8 +.004–.000 +.10–.00
To 4,000 101.6
Over 4,000 101.6 +.005–.000 +.13–.00
To 7,000 177.8
Over 7,000 177.8 +.006–.000 +.15–.00
To 12,000 304.8
Over 12,000 304.8 +.007–.000 +.18–.00
To 20,000 508.0
Over 20,000 508.0 +.008–.000 +.20–.00
Eccentricity: The allowable amount of radial
runout from the sprocket bore to the O.D. is shown
in Table 20.
Table 20 – Sprocket Eccentricity
Outside
Total Eccentricity
Diameter Total Indicator Reading
(in) (mm) (in) (mm)
Up to 2 50 0.0025 0.06
Over 2 50 0.003 0.08
To 4 100
Over 4 100 0.004 0.10
To 8 200
Over 8 200 .005 per inch .013 per mm O.D.
O.D. over 8 " over 200 mm
(may not exceed face diameter
tolerance)
Table 21 – Bore Tolerance for MPB
Sprockets
Bore
Bore Tolerance
(in) (mm) (in) (mm)
Up to 1.000 25.4 +.0010 – .000 +.025 – .000
Over 1.000 25.4 +.0015 – .000 +.038 – .000
To 2.000 50.8
Pitch Accuracy: Adequate pitch to pitch accuracy
is generally more difficult to achieve with molded
sprockets than with machined sprockets.
Recommended tolerances are listed in Table 22.
Table 22 – Sprocket Pitch Accuracy
Accumulative
Pulley O.D. Pitch to Pitch over 90°
(mm) (in) (in) (mm) (in) (mm)
Up to 25.40 1.000 ±.001 ±0.025 ±.0025 ±0.064
Over 25.40 1.000 ±.001 ±0.025 ±.0035 ±0.081
To 50.80 2.000
Over 50.80 2.000 ±.001 ±0.025 ±.0045 ±0.114
To 101.60 4.000
Over 101.60 4.000 ±.001 ±0.025 ±.0050 ±0.127
To 177.80 7.000
Over 177.80 7.000 ±.001 ±0.025 ±.0060 ±0.152
To 304.80 12.000
Over 304.80 12.000 ±.001 ±0.025 ±.0065 ±0.165
To 508.00 20.000
Over 508.00 20.000 ±.001 ±0.025 ±.0075 ±0.191
Helix Angle: Grooves should be parallel to the
axis of the bore within 0.001 (0.025mm) per inch
(25.4mm) of sprocket groove face width.
Draft: The maximum permissible draft on the
groove form is 0.001 (0.025mm) per inch (25.4mm)
of face width and must not exceed the O.D.
tolerance.
Parallelism: The bore of the sprocket is to be
perpendicular to the vertical faces of the sprocket
within 0.001 (0.025mm) per inch (25.4mm) of
diameter with a maximum of 0.020 (0.51mm) total
indicator reading.
Balancing: Balancing is often not required on
machined metal sprockets. All sprockets should be
statically balanced to 1/8 oz. (3.5 grams) in all
sizes. Drives exceeding 6500 ft./min. (33 m/s) may
require special materials, and should be
dynamically balanced to 1/4 oz. in. (1.78 newton
millimeters)
Production sprockets should be produced as closely
to these tolerances as possible to maximize drive
performance.
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