So, yesterday I was trying to mill holes in a series of angled aluminum brackets. I originally started with a helical drilling tool path and a 1/8" single flute endmill from one of those cheaper ebay 10 packs that a lot of people start out with so they can save money when they break one. As you can see I have broke a few because these are the remnants of two different 10 packs. Anyways, they are way longer in than they should be and the endmill was flexing a bit and was not cutting very well so I stopped and inserted some 1/8 inch drill bits I bought awhile back and had forgot about. My tool paths were drill, change to the endmill rezeroe Z and helical drill to get the required 4.3mm hole size. I followed that with a finishiing helical pass. It was working ok, but on my second plate I forgot to re-zero the Z for the drill which was significantly longer than the endmill. I learned two things quickly: 1) I was way to conservative on my peck drilling tool path depths because that drill plunged straight through that 3/16 inch aluminum real quick and; 2) when your drill bit breaks because it is not retracted high enough, it makes a much better drill bit. Seriously. I pulled the broken piece out of the collet replaced it with the now shorter bit and the drilling was much better with no minute walking of the bit. At the beginning of this project I had wished I had stubby endmills for machining aluminum plates but did not want to delay any further. After this happened I grabbed one of those "too long" cheap Chinese endmills, picked a length I wanted, placed it in my vise grips, walked over to my vise, and snapped of the unneeded length. I cleaned up the broken end on my bench grinder. I was much happier with the helical drilling after making the endmill shorter. My new awesome 1/8" drill: My new stubby single flute endmill: Thankfully the 3" side of the bracket required 5.2 mm holes and slots so I was able to step up to a much higher quality 3/16" two flute cutter that worked very well at about 18000 rpms and 900 mm per minute with a 1 mm step down and 6 degree ramp angle. So, morale of the story, save those broken endmills for aluminum plate.
