What Drill bits to use?

I just ordered a nomad CNC mill. I’m a complete “newbie” to cnc work. I have multiple 3D printers and print daily for 3 years… but I expect a big learning curve to start.
I plan on using plastic to start. I need to machine a plastic part 1/2" wide" x 2" long x 1/2 high. What bit should I use? I purchased the HDPE Sheet 3 x 5 x 1 stock from carbide 3 to start with.
I need to mill multiple small parts out of one HDPE Sheet 3 x 5 x 1 sheet. How do I cut all the way through? Do I make all interior cuts then use the last pass to cut the O.D.?

There are some general themes, but some details depend on the software you are using.

  1. the bit needed depends on the material, but more on the particular cut you are making: You would use a square-end bit to machine the flat bottom of a pocket, a “vee” bit for a vee shaped groove, a ball end (really half ball) for round bottom grooves, fillets, and general profiling. These are the basic types for a machine of this size. The bits from C3D are a really good starting point. A search of the archive here will find feed-and-speed recommendations if you are not using the C3D software (meshcam or carbide create) to generate tool path.

  2. when machining multiple parts, or any part that will be cut free from larger stock rather than have all excess cut away as chips, it is common to leave at least some of the boundary material to provide support until the last operation, and, if there isn’t support for the part itself, leave at least a little that gets removed manually after machining (usually using a “tabs” option for the profile slotting cut). If the part has enough bottom surface, and you are fixturing with adhesive, you can free it completely without tabs

If the outer profile is not just a square cut (it ha taper or lots of fine detail), I leave the bottom bit (maybe 0.5 to 1mm for smaller parts) in its entirity until the very end so as to provide support against movement and vibration.

Endmills, not drill bits: https://docs.carbide3d.com/support/#tooling-support

You cut all the way 'round by setting up a profile cut — this is shown at: Adding geometry to cut as a pocket with a finishing pass

Correct, interior cuts first, then the last thing is cutting around the perimeter.

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