7/29/2019 The Principle of This Device is to Mount a Standard Gear on a Fixed Vertical Spindle and the Gear to Be Tested on

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The principle of this device is to mount a standard gear on a fixed vertical spindle and the

gear to be tested on another similar spindle mounted on a similar spindle mounted on a sliding

carriage, maintaining the gears in mesh by spring pressure. Movements of the sliding carriage asthe gears are rotated and indicated by a dial indicator, and these variations are a measure of any

irregularities in the gear under test , alternatively a recorder can be fitted , in the form of a waxed

circular chart and records made of the gear variation in accuracy of mesh.

The gears are mounted on the two mandrels , so that they are free to rotate without

measurable clearance. The left spindle can be moved along the table and clamped in any desiredposition. The right mandrel slide is free to move, running on steel balls , against spring pressure

and it has a limited movement. The two mandrels can be adjusted so that their axial distance is

equal to the designed gear center distance.

When the waxed paper recorder is fitted, the chart makes a revolution for each one of the

gears mounted on the sliding carriage. As the chart moves and rotates, the line traced records the

movements of floating carriage. A circle is drawn at the same time as the record as shown in

figure 12.

Optical dividing head consists of a circular scale, suitably calibrated in degrees and

fractions and fitted concentrically to the axis of the machine spindle. The scale is viewed

through a microscope. It can measure directly upto 12 of arc and readings can be estimated

upto 3 of arc. Fig. 8.9 shows the diagrammatic arrangement of the optical system employed

in optical dividing head. It would be noted that the light passes through a system of lenses and

illuminates the divided scale (mounted on the main spindle) thus projecting the readings on a

ground glass screen. This arrangement thus dispenses with the focusing eyepiece and errors

due to parallex are eliminated. The spindle on which the glass divided circle is mounted, runs

in hardened and lapped plain bearings. The worm which is used only for rotation purposes is

mounted in bearings independent of those for the main spindle. The worm wheel is driven by

the worm, which is connected to a hand-wheel, and a lever is provided for engaging or

disengaging the drive. If handle is turned against the locked spindle, it would simply override.

In order to make a rough check on the required angle, an indexing ring graduated in degrees

is provided at the end of the spindle.