solved problems on indexing methods

SOLVED PROBLEMS ON INDEXING METHODS

Problem 3.13 Direct or rapid indexing

Find index movement to mill hexagonal bolt by direct indexing if the rapid index plate has 24 slots.

Solution:

Number of slots to be moved

After machining, one side of the bolt, index plate has to be moved by 4 slots for 5 times to finish the work. Ans.

Problem 3.14 Plain or simple indexing

Find the crank movement for dividing the periphery of the workpiece into 10 divisions.

Solution:

Crank will be rotated by 4 complete turns for indexing. Ans.

Problem 3.15 Plain or simple indexing

It is required to cut 80 teeth on the workpiece by milling. Find the crank movement.

Solution:

Thus, the crank has to be moved by 10 holes in a 20 hole circle or 12 holes in a 24 hole circle. Ans.

Problem 3.16 Plain or simple indexing

Find the indexing movement for 18 divisions on a plate.

Solution:

Thus the crank has to be moved 2 complete turns and 4 holes on 18 hole circle. Ans.

Problem 3.17 Blain or simple indexing

Determine the indexing crank movement for milling hexagonal bolt by simple indexing.

Solution:

Now, a circle of hole is selected any number that can be divided by the denominator. Say 33.

Thus, the crank will be moved by six complete turn and 22 holes on a 33 hole circle. Ans.

Problem 3.18 Compound indexing

Determine the indexing crank movement for compound indexing for 87 divisions. 

Solution:

Suppose two circles of 29 and 33 holes are selected. Substituting the values in the expression 3.1, (Refer compound indexing on Page 3.132)

Since, the numerator is one, the selected circles are correct.

The required indexing is given by

Taking 3 as common, the above expression becomes

For indexing, the index crank should be moved by 23 holes on 29 hole circle forward direction and then the plate and the crank together is moved by 11 hole on 33 hole circle in backward direction. Ans.

Problem 3.19 Compound indexing

Determine the indexing crank movement for compound index for 69 divisions.

Solution:

Required index movement =

Suppose, two circles of 23 and 33 holes are selected. Substituting the values in the expression 3.1 (Refer compound indexing on Page 3.132).

Since the numerator is unity, the circles selected are correct.

The required indexing movement is given by

Taking 1 as common, the above expressions becomes

Thus, for indexing 69 divisions, the index crank should be moved by 21 holes on 23 hole circle in forward direction and then the plate and the crank together is moved by 11 holes on 33 hole circle in the backward direction. Ans.

Problem 3.20 Differential indexing

Calculate the gear ratio, the indexing movement and the number of idler gears used for milling 119 teeth spur gear on a gear blank.

Solution:

There is no 119 hole circle in an index plate, the divisions cannot be indexed by simple or plain indexing. So, differential indexing is selected.

Assume A = 120

(a) Gear ratio:

(b) Index crank movement:

The index crank will have to be moved by 8 holes on 24 hole circle of each cut for 119 Ans.

(c) Number of idlers:

As (A - N) is positive, a simple gear train with one idler is used. The index plate will rotate in the same direction of the crank movement.

Ans.

Problem 3.21 Differential indexing

A gear blank on the milling machine is to be indexed for cutting 73 teeth. The machine has a 40:1 ratio index head. Calculate the gear ratio necessary between the spindle and index plate.

Solution:

As there is no 73 hole circle in an index plate, the divisions cannot be indexed by simple indexing. Hence, the differential indexing is used.

Let the selected number, A = 70

(a) Gear ratio:

(b) Index crank movement:

The index crank will have to be moved by 12 holes on 21 hole circle for each cut for 73 times. Ans.

(c) Number of idlers:

As (A - N) is negative, a simple gear train with two idler are used.

The index plate will rotate in the opposite direction of the crank movement. Ans.

Problem 3.22 Differential indexing

Find the gear combination and index movement necessary for 139 divisions.

Solution:

Let the selected number, A = 140

(a) Number of idlers:

As (A - N) is positive and gearing is compound, no idle gear is required.  Ans.

(b) Index crank movement:

The index crank will have to be moved by 6 holes on 21 hole circle for each cut for 139 times. Ans.

Problem 3.23 Angular indexing

Calculate the index crank movement for the index of 3°30'.

Solution:

Crank will have to be moved by 7 holes on a 18 hole circle in the index plate. Ans.

Problem 3.24 Angular indexing

Calculate the index crank movement for the index of 18°

Solution:

Index crank movement = 18/9 = 2

Crank will have to be moved by 2 complete turns. Ans.