Stifness Measurements as a Check of Machine-Tool Spindles

In many cases poor performance of machine-tools is related with ill-functioning of the spindle. Kith the aid of a simple set-up we made many diagrams of spindle deflection as a function of load on a variety of old and new machine-tools. In fact it is already an old method, which is however seldom used. The difference is that we use inexpensive electronic equipment which produces continuous diagrams instead of the point to point diagrams obtained by the classical mechanical means. This makes the method usefull for routine measurements and gives more information. In the paper we will show how those diagrams enabled us to trace defects in spindle assembly such as insufficient preload of bearings, misalignment of bearings, defects in spindle drives etc. It seems that the method can serve as a valuable tool for the inspection of machine-tool spindles.