Standard_Parts_Catalogue

Page 353 | 1.4 Adjusting, Positioning, Locking with and without Position Indication GN 200 Indexing Mechanisms continued Indexing mechanisms can be used to adjust shafts or spindles by an angle of rotation of 6º (or a multiple thereof) and subsequently secure them against rotation by engaging in a serration. Applications Description The indexing mechanism is a selfcontained unit with all adjustment and securing elements accommodated in the smallest possible space. It consists of three main parts: - The bushing is connected to the shaft with a parallel key/keyway or crossdowel. - The location ring is fixed; it is mounted on the bushing and connected to the machine by 3 contersunk screws (e.g. DIN 7991-M5). - The knurled hub connects the fixed location ring and the shaft which can be adjusted. When locked, the internal toothing of the knurled hub (60 teeth) simultaneously engages with the external toothing of both the fixed location ring and the bushing connected to the shaft. To adjust the shaft, the knurled hub is pulled against spring pressure, disengaging from the location ring. The knurled hub however remains positively connected with the shaft via the external toothing of the bushing. By turning the knurled hub the shaft can now be adjusted. More information With 60 teeth, the following divisions can be achieved: 2, 3, 4, 5, 6, 10, 20, 30. A simple method provides indexing of the shaft to a limited number of positions only, i.e. every 120°. For this purpose, the location ring is provided with a dowel pin that allows engagement in the serration only if it meets a counterbore in the knurled hub. This counterbore can be manufactured oversize as the dowel is for rough positioning only. Accurate positioning and load capacity is maintained via the engaged teeth. For adjustment with a threaded spindle, it is recommended to assign the the 1.5 mm thread pitch to the standard scale with 60 graduation marks (Type AS) : 1 graduation = 0.025 mm. The serration ensures more accurate and wear-free indexing than individual dowel pins. If a very high torque has to be overcome during adjustment, unlocking and locking is more difficult due to the low backlash respectively the friction in the tooth flanks. In this case, it is recommended to use indexing levers GN 215.