HEJ, HU ISSN 1418-7108 Manuscript no.: MET-000123-A

Examination of the effect of the profile radius on the operation of the thread with measurements

The effect of the thread profile made with improper geometric dimensions on the operation of the gear was examined by measuring the stress acting on the ball returning tube. The measurements in the function of the angular displacement of the pin were performed with nuts of different profile radius.

 

Figure 6: Measurement of a gear having a nut thread profile of larger connecting angle than the nominal one

 

Figure 7: Driving torque and thread stress of a gear having a nut thread profile of larger connecting angle than the nominal one

First measurements were performed on a gearbox with a nut thread profile machined to a smaller radius than the nominal size, for small load. It is well visible on Fig. 6 that for entering and leaving of every third ball large ear- stress originated and peak values appeared on the diagram of the driving torque at the same frequency.

The same measurement series was carried out for a gearbox with a nut thread of a nominal arc radius.

Figure 7 shows the pin torque and ear stress diagram of the thread of a nut profile regarded as good taken at the largest load in the function of the displacement. Compared to the earlier narrow thread profile the ear stress is insignificant and despite to the almost double load the periodic character, which could be observed on the earlier function appearing on the torque-curve cannot be seen as well.

 

Figure 8: Measuring of the set deformation of the ball returning tube ear and the deterioration of the thread

The ball returning tube in the gearbox having a nut of a closed profile exposed to a heavy load suffered a set deformation and cut-like damages came into existence on the balls (Fig. 8).

HEJ, HU ISSN 1418-7108 Manuscript no.: MET-000123-A