Modular drill jig and method of making same

A drill jig comprising a bushing plate adapted to have one or more drill guide bushings located therein, and means for clamping a part to be drilled to said bushing plate, said bushing plate having at least two precision machined flat and adjacent right angle edge faces defining orthographic reference planes for use as a reference in locating precisely the orthogonal coordinates of the drill guide bushings in said bushing plate, said means for clamping including a tool plate, said tool plate also having at least two precision machined flat and adjacent right angle edge faces, said bushing and tool plates having opposed clamping faces which are precision machined flat at right angles to the respective precision machined edge faces thereof, said clamping face on said tool plate having locating means for positioning in relation to said bushing plate a part to be drilled, said precision machined edge faces on said tool plate defining orthographic reference planes for use as a reference in locating precisely the orthogonal coordinates of said locating means on said tool plate, an at least two guide posts fixed in respective guide post bores in one of said plates at right angles to the clamping face thereof and slidably received in respective guide post bores in the other of said plates and cooperative therewith to maintain parallel and vertically aligned the clamping faces of said plates, the corresponding precision machined edge faces of said bushing and tool plates also being co-planar.