Unitary internal/external extension plate for a jig grinder

A unitary one-piece precision tool accessory to selectively extend either the internal or the external grinding capacities of a jig grinder machine comprising;

• an elongated generally rectangular extension plate having:
• (1) a first surface on a first side of said plate adapted for grinding internal diameter holes,
• (2) a second surface on a second side of said plate parallel and opposite to said first surface and adapted for grinding external diameter holes,
• (3) longitudinally extending parallel side walls spaced apart from one another laterally,
• (4) transversely extending parallel end walls spaced apart from one another longitudinally,
• said plate member having formed therein a through opening disposed inwardly of one of said end walls and each of said first and second surfaces having formed therein a cylindrical concentric recess counterbored relative to a corresponding side of said through opening, thereby to selectively receive a driving eccentric of a dove tail slide on a jig grinder machine,
• and first and second sets of counterbored drilled through holes in corresponding of said first and second surfaces and by means of which said plate may be connected in firm assembly with the dove tail slide of the jig grinder machine,
• each set of said first and second sets of counterbored drilled through holes being disposed in a pre-aligned keyed location,
• and a plurality of tapped recesses in said first and second surfaces disposed in rows and columns for effecting selected engagement with a grinding tool.