I’ve just finished another six of the DF9IC 23cm PA heat spreaders. By the time I get good at this, I won’t need to make any more!
100mm x 71.4mm x 12mm copper, with a 0.65mm x 10mm milled slot, 8mm coax link pocket, 3 x 4.5mm mounting holes and 8 x 3mm threaded and relieved PCB mounting holes.
Edges are milled with two-flute fast taper 16mm HSS end mill, slots with 10mm and 6mm two-flute slot drills
Tapped holes are drilled 2.7mm clear, then relieved on the back with 3.5mm drill to 6mm deep. The remaining 6mm is tapped using a thread-forming tap from the underside. I used Westway high-pressure tapping oil.
Close-up view of underside showing three 3.5mm clearance holes with 3mm formed thread in the lower half, and one of the 4.5mm mounting holes. Also shows the decent finish from that huge end-mill. Much nicer than the chattery finish from the flycutter I used previously.
Corners are milled to clear the overlap seam in a standard tinplate box. Holes are deburred using a single-hole countersink bit. Edges deburred with a deburring tool. Faces and edges polished with a Scotchbrite rotary mop.
All machining was done on my ancient Bridgeport 3HP mill with varispeed head and soft-start inverter.