Took my first go at aluminum today. After many weeks of watching tutorials and looking at speeds and feeds for the parts I'm making I'm confident in the pocket and contour actions. Up till now I have cut would and plastics using these two methods and when I needed to drill a hole I either drilled a 0.25" hole or used a center drill to spot a starter hole. The center drill DID NOT turn out well. I tried using a simple single .125" flute end mill to spot a hole but that left a dome in the hole. Also tried a .125 ball end that plunged 0.5mm to mark the spots for future hand drilling. What other options have you used to drill holes if any?
in general, drill holes with drills, endmills do not drill well or, helical bore the .25" holes with a 1/8" or 3/16" end mill (square not ball end)
Depends what your machine is. I would doubt that most of these cantilevered, plastic-wheeled extrusion machines have the rigidity to deal with the tool pressures involved in drilling ops, at least at anything over maybe 3-4mm (where the weight of the spindle can do a lot of the work). Though I guess there they could do a lot of step-enlarging to keep pressures low. Instead, what you likely need to do (assuming you're running an extrusion machine) is to use an end mill, probably 2 flute for chip evacuation, about 1/3-2/3 of the size of the hole you're trying to drill, and interpolate the hole with a helical boring path. Edit: ninja'd by David. Though I had missed that you weren't using real drill bits. Yeah, that's definitely part of the problem.
Sorry, yes machine type would have helped. So yes it's a Workbee1010 with a Dewalt. Thanks for the input, turns out my tests confirm your suggestions. For the small holes that need to be tapped. Marking them with a small endmill and hand drilling later will be the best course of action. I'm making new end plate that recesses thrust bearings to replace the radial bearings supporting the lead screws. Here is my first cuts on aluminum.
As others have mentioned, helical is the way to go. I use a 1/8 for 1/4 inch holes and I do a rough cut then a finishing cut. I do this in wood and plastic too if the holes have to be real precise.
