Anyway, I own a table saw, drill press, 3D printer and a little home made CNC router that I use to make mandolins. I have found that if I take off only a little bit of material at a time, about .020", I can shave down a block of 6061 aluminum to most any shape. Oh about materials, since I will probably trash the thing when I am done, I don't want to spring for exotic material such as 7075 aluminum (I know its not that exotic, but I don't have any). I have some 6061 bar and some 01 tool steel in my scrap heap, so I am using that. I will make the frame from the 6061 and the rails from the tool steel. the rail inserts will be pinned and epoxied into place. You'll see. My design methods do not revolve around what is the easiest, or most producible, or even the what makes most sense. I design for what I got laying around the house.
Interesting project. Someone on here just did some very nice grips for a 1911 that turned out amazing. 6061 aluminum is pretty nice stuff and you can do a great deal with it so I think you are good in that area.
OK, to get started. First I wacked off (hmmm) a 6.5" length of 6061 1" X 1.25" bar and mounted my drill guide. The drill guide is made on the 3D printer, which happens to be pretty dad gum accurate, using 1.75" long 1/8" dowel pins to precisely locate it to the bar. I then use a spot drill to just kiss the aluminum bar to mark each hole location.
Whoa, I hear you say. You need more that a 1" X 1.25" bar stock to fab a 1911. I say look at the STI style 2011 gun with a polymer handle and you might begin to get the jist.
Next drill the holes with a .120" bit (1/8" dowell pins are not 1/8" round, they are .120" so why don't they call them 3/25" dowel pins?) all except a couple that are smaller.
Several of the holes are for locating dowel pins. For example, below is how the piece will be oriented for the Magwell machining operation.
Ya gotta stand on your head for this one
The magazine well and the hole for the disconnector need to be machined at an off angle. The disconnector hole is a bit tricky since I am drilling into an angled surface. I use a flat end mill to just kiss the surface and make a little flat area that I can then use a spot drill, then an actual drill to precisely place the hole. If you try to spot or drill in a slanted surface the drill will walk down hill before it bites.
In the first picture you will notice an Ohm meter. I connect one lead to the work piece and the other to the router body. My meter has a buzzer that lets you know when you have continuity, I use this to zero my mills to the work piece or the locator dowel pins. this is how I can precisely align my machining operation to the part, switch tools and repeat.