Shrink Fitting of Bearings

Objective

To heat a roller bearing assembly for a shrink fitting application

End Product

roller bearing

Equipment

Ambrell 7.5 kW, 150-400 kHz induction power supply, equipped with a remote heat station containing two 1.5 µF capacitors (for a total of 0.75 µF

Materials

• Steel tubes 7” OD x 4.75” ID x 5” heat zone • Type ‘K’ thermocouple to measure temperature • Thermal blanket

Temperature

500, 800, 1000 *F (260, 427, 538* C)

Frequency

166 kHz

Testing

Initial tests were completed on a sample without a thermal blanket. A thermocouple is slipped between the copper ring and the steel tube to measure temperature. The part measured 4.940” (at room temperature with an ID gauge.) The part reaches 1000F (538C) in about 10 minutes.

Benefits

The part measures 4.975” at 1000°F yielding an expansion of 0.035” (4.975 minus 4.94). At 500 and 800F the expansion numbers were 4.950 and 4.964 respectively.

When using a thermal blanket the heat time is reduced by about 90 seconds (8.5 minutes as opposed to 10 minutes).

Image