GN 200-STIndexing mechanisms

Indexing mechanisms GN 200 replace and simplify complicated indexing and safety mechanisms, such as indenting levers, latching mechanisms, indexing pins and other securing elements.

Besides the standard scale (Type AS) the control knob version may be supplied with any scale. In such cases, it is recommended to use the matte chrome plated version since the color contrast is better. (Version in Steel ST)

Regarding design, numbering run, numbering position and numbering sequence of the scale please see the layout for scale rings on the order sheet  'How to order graduations' .

• Special graduations see 'How to order graduations' 

• ISO-Fundamental Tolerances 

• Stainless Steel characteristics 

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.

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.

• 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 limited number of positions only, i.e. every 120°. For this purpose, the location ring is manufactured with a dowel which allows engagement only when the bushing is provided with a corresponding hole (see assembly examples). This hole can be manufactured oversize as the dowel is for rough positioning only. Accurate positioning is maintained via the 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.

The size of numbers and length of graduations depend on the number of graduations, quantity of numbers and the scale ring diameter. The scales are engraved with laser precision.