3.4
3.4.1
Shaft Materials
Most motor manufacturers use SAE 1045 in either cold-rolled or hot-rolled steel (CRS or HRS). Other materials include sulfurized SAE 1117, SAE 1137, SAE 1144, hot-rolled SAE 1035, and cold-rolled SAE 1018. A ground stock of any material is used on special CNC Swiss turning machines.
Generally, the cold-rolled and sulfurized steels will cost about 15 percent more than HRS and will machine better. Machining trials need to be performed in order to justify the extra cost. Since all shaft-turning machines perform differently, there is no established material or machining practice.
Obviously, the hot-rolled plain carbon steel, on a cost-per-pound basis, is cheaper than cold-rolled sulfurized steel. But there are tradeoffs. The hot-rolled material has to be sized larger than cold-rolled because of the lack of outer diameter (OD) control in the rolling process. A manufacturer has to evaluate whether the larger-size and lower-material-cost hot-rolled bar stock is more or less costly than cold-rolled bar stock. Also, the hot-rolled material, by the very nature of its processing, has hard and soft spots, residual stresses, voids, and other material deficiencies, making machining more difficult. Again, machine trials need to be conducted to obtain the best cost option between CRS, HRS, nonsulfurized, and sulfurized materials.
Because of the difficulties with HRS, most motor manufacturers will use sulfurized CRS.
