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Belt-winding core specifications

Standard Core

Outside Diameter

Square Inside Dimension

Safe Working Load
(Based on
Core Length)
5″ 2.25″ 45 lb/in
6″ 3.25″ 35 lb/in
7″ 3.25″ 60 lb/in
8″ 4.25″ 50 lb/in
10″ 4.25″ 100 lb/in
12″ 6.25″ 79 lb/in

Not sure? Try our standard belt-winding core sizing tool.

Paper-wound Core

Outside Diameter

Square Inside Dimension

Safe Working Load
(Based on
Core Length)
5.5″ 2.25″ 70 lb/in
6.5″ 3.25″ 57 lb/in
7.5″ 3.25″ 87 lb/in
10.5″ 4.25″ 135 lb/in

Staved Core

Outside Diameter

Square Inside Dimension

Safe Working Load (Based on
Core Length)
8.5″ 2.25″ 156 lb/in
9.5″ 4.25″ 140 lb/in
11.5″ 4.25″ 220 lb/in
13.5″ 6.25″ 186 lb/in

Note: These are suggested safe working loads. It is strongly recommended that customers do further testing under their in-plant conditions to ensure optimal performance. The safe working loads shown above are not intended to account for winding bar induced torsional shock loads imposed by sudden acceleration or deceleration.

Download our Belt-Winding Core product sheet.

Download our Notched Core product sheet.

Don’t see the size you’re looking for? Our engineers can also custom design and manufacture cores to meet specific-use demands (e.g., round holes, variable lengths).