What index plate should be used to mill a spur gear with 28 teeth using a simple indexing method, and how many revolutions are required?
In order to mill a spur gear with 28 teeth using a simple indexing method, we should use index plate 2 with 33 hole circles. The number of revolutions required is approximately 0.966.
Understanding the Indexing Head in Milling Machine
In milling operations, the indexing head is a crucial tool that allows for precise rotation of the workpiece at specific intervals to achieve accurate machining results. One common application of the indexing head is in milling gears, where a series of equally spaced teeth need to be cut to create functional gears for various mechanical applications.
Choosing the Right Index Plate
When it comes to milling a spur gear with a specific number of teeth, the selection of the correct index plate plays a vital role in achieving the desired outcome. In the provided data, two index plates are available:
- Plate 1: 15, 16, 17, 18, 19, 20 hole circles
- Plate 2: 21, 23, 27, 29, 31, 33 hole circles
To determine the appropriate index plate for milling a spur gear with 28 teeth, we must calculate the ratio between the number of teeth on the gear and the number of holes on each index plate.
Calculating the Ratios
- For Plate 1: We have a gear with 28 teeth, and the closest number of holes on Plate 1 is 20. The ratio for Plate 1 is 28/20 = 1.4.
- For Plate 2: The closest number of holes on Plate 2 to 28 teeth is 29. The ratio for Plate 2 is 28/29 ≈ 0.966.
Determining the Best Index Plate
The key factor in selecting the appropriate index plate is to choose one with a ratio closest to 1. In this scenario, Plate 2 has a ratio of 0.966, which is closer to 1 than the ratio of Plate 1 (1.4). Therefore, Plate 2 is the optimal choice for indexing when milling a spur gear with 28 teeth.
Calculating the Number of Revolutions
To find out the number of revolutions required, we divide the number of teeth on the gear (28) by the number of holes on the chosen index plate (29). The result is 28/29 ≈ 0.966 revolutions, which is the approximate number of rotations needed to mill the spur gear accurately.
In conclusion, by correctly selecting the index plate with the closest ratio to 1 and understanding the number of revolutions required, machinists can efficiently mill gears using simple indexing methods in milling machines.