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Monday, 21 July 2014

Milling Machine Indexing Method

Milling Machine Indexing Method Points : Milling Machine Indexing Method, Index Plate, Simple Indexing, Compound Indexing, Differential Indexing, Direct Indexing, Plain Indexing, Indexing Operation There are different indexing methods are given below:
1. Index Plate
2. Simple Indexing
3. Compound Indexing
4. Differential Indexing
5. Direct Indexing
6. Plain Indexing
7. Indexing Operation
1. Index Plate Index plate is round metal plate by a series of six or extra circles of evenly spaced holes; the index pin on 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 obtain. Following sets of plates are normal equipment:
(a) 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

(b) Cincinnati type, one plate drill on equally 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 milling machine is passed out through use also a plain indexing head or universal dividing head. This process of indexing involves use of worm, crank, index head and worm wheel. Worm wheel usually carries 40 teeth with the worm is single threaded. By this arrangement, as a crank completes one revolution, work wheel turn through 1/40th of revolution. Also a worm wheel turn through 2/40 (1/20)th of revolution, and presently Therefore, for one revolution of workpiece, a crank wants to create 40 revolutions. Holes in index plate extra help in subdividing rotation of workpiece. 3. Compound Indexing As the number of divisions necessary on job is external the vary of simple indexing, method of compound indexing is use. Operation is passed out by provide two detach simple indexing movements.
(a) By turning crank in similar way as in simple indexing.
(b) Once more turning index plate and the crank also in equal or in the conflicting directions.
4. Differential Indexing At times a number of divisions are necessary which cannot be achieving through simple indexing by the index plates frequently supplied. To get these divisions a differential index head is use. Index crank is attached to worm shaft with a train of gears in its place of through a direct coupling and with simple indexing. Selection of these gears occupy calculations like those use in calculating change gear ratio for cutting threads on lathe. 5. Direct Indexing Creation of several index heads allows the worm to be detached as of the worm wheel, creation possible a faster way of indexing, call direct indexing. Index head is give 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 index head spindle. Motionless plunger in index head fits the holes in index plate. Through moving the plate with hand to index directly, spindle with workpiece turn an equal distance. Direct index plates generally have 24 holes and present a rapid means of milling squares, hexagons, taps, and so on. Some number of divisions which is factor of 24 can indexed rapidly and suitably by direct indexing method. 6. Plain Indexing Following principle affect to necessary indexing of workpieces:
(a) 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.

(b) Equal rule affect 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 turns also, to index for 14 spaces, 14 divided in 40 equals 2 6/7 turns. Thus, follow rule can consequent: to agree on the number of turns of index crank desired to take one division of every number of equal divisions on workpiece, divide 40 by number of equivalent divisions preferred give worm wheel has 40 teeth, which is standard practice.
7. Indexing Operation Two follow exemplar explain how index plate is use to get any preferred part of a entire spindle turn by plain indexing.
(a) 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 turn on any circle whose figure of holes is detachable by 3. Thus, six full turns of 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 workpiece.

(b) 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 or 20 spaces on 21-hole circle. To apply the rule given, choose a circle have 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 entire circle. As counting holes, start by the first hole to the fore of index pin.

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