Just finished these two bridges. I machined 6061 Aluminum (.375 x 4). I was running 50 IPM with .004 DOC on a 2 flute, up cut .25 bit. For drilling, I used a .125 bit from McMaster Carr…not using any type of coolant. I am using Fusion360 for CAD and CAM and then running the Gcode through EASEL.
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