A seemingly minor, but very important part of my 1911-ish project are the grips. It's the grips that will hold the 3D printed lower onto the machined upper frame. As such, they needed to be made out of something more substantial than plastic, so I made them out of aluminum. I had trouble deciding on what kind of pattern I wanted, so I decided to stick with the classic double diamond. Tedious to draw on my old slow machine, but it turned out well. I spaced the checkering far enough apart so that most of it could be reached with a 1/16" ball mill, then basically did a constant stepover across the whole thing with the cutter stepping over .005" at a time.
Unlike regular 1911 grips which are just sort of there, these ones are machined to as tight a tolerance as I can reasonably hold so that they locate accurately and repeatable on the grip screw bushings. All the critical tolerance features were machined in one setup on the back side, so to machine the top side instead of using a fancy jig or fixture, I stole an idea from work and bolted them to a subplate. I have a plate with 1/4" holes spaced every 1/2" so that for the 2nd side operations, I can simply bolt the block of aluminum down with 1/4" bolts. I added some tabs to my CAD file for the bolt hole bosses to attach to. Here's how it looked fresh off the machine:
The leftover tabs are only .050" thick, and it was quick work to trim them off and file the edges flat:
Here's a closeup of the checkering. The diamonds are spaced .100" peak to peak, and each diamond has a .019"x.040" flat at the top so that it's textured without feeling sharp.
Here's how it looks in Solidworks. Everything is spaced as far apart as it is because I planned from the get go to cut it with a 1/16" ball end mill, and there are no fillets drawn at the bottom of the checker diamonds though I knew they would end up filleted anyway because of the cutter radius. The gap between the diamonds is just enough so that the tip of the ball mill hits the bottom surface. The finish machined part doesn't exactly match the CAD drawing because of that, but with my old slow computer it was easier to let the cutter do the work instead of trying to draw exactly what I wanted.
