Overview
The single task that can ruin a panel is the most basic - drilling instrument mounting holes. Having tried with the lower panel to mark out holes for the 1 1/4 instruments only to find the need to fine tune each hole I decided to use the instrument as a jig.
Marking out
Guide lines were marked out on the panel using the base of the panel, square and felt tip pen.
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| Adding vertical references at various locations |
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| Locating the instrument's average center See notes below |
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| Ready to mark final two holes |
With the a single instrument in an opening it was moved vertically and horizontally and its average position marked referencing the layout marks. Two instruments were placed into a pair of the openings with a ruler across one side to square them up about the horizontal average line's. Next the transfer punch was placed into a mounting hole and the panel marked.
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| Transfer punch used for marking |
Note: A hex 1.5 mm drill was used as it was short and stiffer than a standard twist drill.
The hole was drilled using a hex 1.5 mm drill then enlarged to 9/64'' to suit a 6-32 screw, next the instrument was fitted back to the panel with a screw, tightened around the average horizontal and appearance checked from the front, then repeated at the diagonal mounting point.
Refitted with two screws, tightened and the final two holes marked and drilled.
This process is repeated for all the instruments and when the trial assembly conducted, all but one instrument was square and this was only a few degrees. Best of all the 1 1/4'' gauges were square when fitted as these have the least tolerance for any errors.
Comment
To avoid all this work and achieve a perfect job draw the panel, produce a DXF file and have it CNC machined.
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