Shrink Fitting
Client 1.
A large North West based pump repair company called on our services to assist in assembling two bearing sleeves and a drive coupling onto a 270mm diameter 4 metre long shaft. The dimensions were checked and a few small blemishes were fettled.
The procedure was to immerse the shaft, or in the case of a long shaft - 'the end', into a bath of liquid nitrogen, which after a predetermined time will have cooled to a point where maximum shrinkage will have occurred.
The shaft was taken out of the bath and the first of two bearing sleeves was offered over the shaft to the required position where it was held in place with a retaining bolt. The shaft was reversed and the second end cooled. Then the second bearing sleeve was fitted and located with a retaining bolt. The shaft was immersed again in the bath for a further period of time, when it was removed and lowered into the coupling.
The coupling had been placed on a machined plate and levelled. The shaft was lowered into the coupling until it made contact with the plate, which was dimensioned to allow the shaft to enter the coupling to a predetermined depth, thus maintaining the correct space between the bearing sleeve and the coupling.
The shaft onto which the bearing sleeve has already been fitted is offered into the drive coupling.
Client 2.
A North West aero component manufacturer used our services to shrink fit 102 stainless steel bushes into a turbine ring gear. The bushes, although only 1.7" diameter, were ground to very fine tolerances, and in order to obtain the correct interference fit without spalling, it was necessary to also warm the ring gear to about 250°C. Once the assembly had returned to room temperature the bushes were honed to finished size.
