Machining fixture for VHF PA Heatspreaders

Part of the design decision for the spreaders I made for the VHF PAs was to use pockets machined in the copper surface of the spreader to carry the MRF151 transistors, which protrude 2mm below the PCB. As I don’t have a CNC mill, I had to make a fixture to hold the spreader accurately in place while I machines the pockets on my Bridgeport.

Finished item, those pockets are at 45 degrees
Finished fixture with a spreader ready to mill
Slot where the spreader sits, before the holes for the clamps were made
Underside showing vice clamp
Cam to press the spreader against the reference surface of the slot
toe-clamps to hold the spreader in place for machining

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