PRECISION TOOL MAKING 



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The master plate Is mounted on the die block and located by means 

 of two snug fitting pins driven into the block and projecting into 

 the two aligning holes near each end of the plate. The die block and 

 plate are then attached to the face plate of a bench lathe, as shown in 

 Fig. 17. Each datum hole in turn is accurately centered with the 

 lathe center by means of the indicator shown in the figure, the master 

 plate removed, and the hole bored in the die block. In centering with 



Fig. 18 — Filing out die openings with filing attachment on bench lathe. 



the indicator, the lathe is rotated and the master plate and die block 

 shifted until the indicator pointer shows but little, if any, movement. 

 With an indicator multiplying the movement 100 times, shifting the 

 plate .0001 in. would move the pointer over the scale .010 in. or 

 .0001 in. eccentricity of the hole would show a pointer movement of 

 .020 in. The master plate gives a permanent precise outline of the 

 important holes, radii, contours, etc., which can be utilized to con- 

 siderable advantage in checking after heat treatment, and especially 

 in making additional tools or replacement die sections. 

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