Simple Indexing in Milling Machine:
The index plate is a circular plate consisting of a series of six or more circles of evenly spaced holes; the index pin on the crank can be inserted into any hole in any circle. Interchangeable plates are regularly furnished with the most divided heads, the required spacing for most gears, bolt heads, milling cutters, splines, etc. Can be obtained. The following are the two most common sets of plates used as standard equipment.
There are different indexing methods are given below:
- Index Plate.
- Simple Indexing.
- Compound Indexing.
- Differential Indexing.
- Direct Indexing.
- Plain Indexing.
- Indexing Operation.
#1. Index Plate-
An index plate is a round metal plate with a series of six or extra circles of evenly spaced holes; the index pin on the crank can put in in any hole in any circle.
By the similar plates frequently furnished through most index heads, the spacings needed for most gears, bolt heads, splines, milling cutters, and so forth can be obtained. The following sets of plates are normal equipment:
Brown and Sharpe type, 3 plates of 6 circles, every drilled in this way:
- Plate 1- 15, 16, 17, 18, 19, 20 holes
- Plate 2- 21, 23, 27, 29, 31, 33 holes
- Plate 3- 37, 39, 41, 43, 47, 49 holes
Cincinnati type, one plate drill on equal sides by circles divided in this way:
- First side- 24, 25, 28, 30, 34, 37, 38, 39, 41, 42, 43 holes
- Second side- 46, 47, 49, 51,53, 54, 57, 58, 59, 62, 66 holes
#2. Simple Indexing-
Simple indexing on a milling machine is passed out through the use also a plain indexing head or universal dividing head. This process of indexing involves the use of a worm, crank, index head, and worm wheel.
The worm wheel usually carries 40 teeth, with the worm is single-threaded. By this arrangement, as a crank completes one revolution, the work wheel turns through 1/40th of the revolution.
Also, a worm wheel turns through 2/40 (1/20)th of revolution, and presently, therefore, for one revolution of a workpiece, a crank wants to create 40 revolutions—holes in index plate extra help in subdividing rotation of the workpiece.
#3. Compound Indexing-
As the number of divisions necessary on the job is external, the vary of simple indexing methods of compound indexing is used. Operation is passed out by providing two detach simple indexing movements.
- By turning crank in a similar way as in simple indexing.
- Once more, the turning index plate and the crank also in equal or in conflicting directions.
#4. Differential Indexing-
At times a number of divisions are necessary, which cannot be achieved through simple indexing by the index plates frequently supplied. Get these divisions; a differential indexed is to use.
Index crank is attached to worm shaft with a train of gears in its place through direct coupling and with simple indexing. Selection of these gears occupy calculations like those use in calculating change gear ratio for cutting threads on the lathe.
#5. Direct Indexing-
The creation of several index heads allows the worm to be detached as of the worm wheel, creation a possible faster way of indexing, call direct indexing. Index head is given by a knob which, as turned during part of a revolution, function an unconventional and disengage the worm.
Direct indexing is able by an additional index plate fixed to the index head spindle. The motionless plunger in the index head fits the holes in the index plate. By moving the plate with hand to index directly, the spindle with the workpiece turns an equal distance.
Direct index plates generally have 24 holes and present a rapid means of milling squares, hexagons, taps, and soon. Some number of divisions which is a factor of 24, can be indexed rapidly and suitably by the direct indexing method.
#6. Plain Indexing-
Following principle affect to necessary indexing of workpieces:
- Assume it is preferred to mill spur gear by 8 equally spaced teeth. As 40 turns of index crank will turn spindle one full revolve, one-eighth of 40, or else 5 turns of crank after every cut, will space gear for 8 teeth.
- The equal rule affects whether or not divisions necessary divide equally into 40. As, if it is preferred to index for 6 divisions, 6 divided into 40 equals 6 2/3 also turns, to the index for 14spaces, 14 divided in 40 equals 2 6/7 turns.
- Thus, follow the rule can consequence: to agree on the number of turns of index crank desired to take one division of every number of equal divisions workpiece, divide 40 by a number of equivalent divisions preferred to give worm wheel has 40teeth, which is standard practice.
#7. Indexing Operation-
Two follow exemplar explain how to index plate is used to get any preferred part of an entire spindle turn by plain indexing.
To Mill a Hexagon:- By the rule over, divide 40 by 6, which equals 6 2/3 turns, or six full turns plus 2/3 of a turn on any circle whose figure of holes is detachable by 3. Thus, six full turns of the crank plus 12 spaces on an 18- hole circle or six full turns plus 26 spaces on a 39-hole circle will make the preferred rotation of the workpiece.
To Cut a Gear of 42 Teeth:- By rule over, divide 40 by 42, which equals 40/42 or 20/21 turns, 40 spaces on 42-hole circle or20 spaces on the 21-hole circle. To apply the rule given, choose a circle that has a number of holes dividable through the required fraction of turn concentrated to its lowly terms. The number of spaces among the holes gives the preferred fractional part of the entire circle. As counting holes, start with the first hole to the fore of the index pin.