Indexing head
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An indexing head, also known as a dividing head or spiral head,[1] is a specialized tool that allows a workpiece to be circularly indexed; that is, easily and precisely rotated to preset angles or circular divisions. Indexing heads are usually used on the tables of milling machines. They are commonly used to machine the flutes of a milling cutter or reamer or the teeth of a gear.[2]
The tool is similar to a rotary table except that it is designed to be adjustable through at least 90°. Most adjustable designs allow the head to be tilted from 10° below horizontal to 90° vertical, at which point the head is parallel with the machine table.
The workpiece can be held with a collet in the indexing head, or between centers with the help of an accompanying tailstock.
Contents
Manual indexing heads
Manual indexing heads use an index plate with various numbers of equal divisions. For example, an indexing plate might have three rows of holes with 24, 30, and 36 holes. This allows the indexing head to index to any number of divisions that can divide into any of those numbers. Index plates with up to 400 holes are available.[2] There is also a permanent indexing plate attached to the collet, called the direct indexing plate, to provide divisions for the most common angles, such as 90°, 45°, and 30°.[3]
Brown and Sharpe indexing heads include a set of 3 indexing plates. The plates are marked #1, #2 and #3, or "A", "B" and "C". Each plate contains 6 rows of holes. Plate #1 or "A" has 15, 16, 17, 18, 19, and 20 holes. Plate #2 or "B" has 21, 23, 27, 29, 31, and 33 holes. Plate #3 or "C" has 37, 39, 41, 43, 47, and 49 holes.[citation needed]
CNC indexing heads
The development of computer numerical control (CNC) has helped to automate the mathematics involved in creating the toolpath for a particular helix. CNC indexing heads and rotary tables are wired to the control and are labeled with their own axis name, just as with the other axes of the machine. However, regardless of the extent to which computer software eases the calculations, the fundamental principles of indexing are the same as those in manual control.
References
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- Burghardt, Henry D. (1922), Machine tool operation, 2, McGraw-Hill.
External links
de:Teilapparat uk:Ділильна головка- ↑ Burghardt 1922, p. 244.
- ↑ 2.0 2.1 Barnwell, George W. (1941), The new encyclopedia of machine shop practice, W.H. Wise & Co., pp. 234–235.
- ↑ Burghardt 1922, p. 245.
