1911 80% Project

Introduction

This was my first attempt at building up a new 1911 from an 80% frame. I'd reworked others in the past and assembled a couple from kits but this marked the first time I'd ever attempted a build from all new, quality, unfitted parts. Below I have documented my journey into the world of custom 1911 builds.

The Frame

The 80% complete frame was purchased from Kristi Tool. It sat around for a few months while I worked on other projects, but one thing I have learned about doing 80% firearm projects is that you should buy the frames when they are available, because the supply can be erratic. I believe I paid $150 for the frame. Ostensibly the frame needed only the slide rails cut, along with the barrel link relief cut. Everything else is supposed to drop in with minor fitting.

As you probably can see from the photos, the frame was machined in two halves, then brazed together in an industrial furnace. This is obviously a departure from the usual manufacturing methods, but I have been reassured of the strength of the weld. Also, the designer saw fit to include a finger grip and tactical rail extension on the dustcover. At this point I wasn't sure what I would do with these, but I decided to leave them for now.

Cutting the Rails

The first and most critical machining operation is that of cutting the rails. Now, I had a set of good blueprints (in addition to Jerry Kuhnhausen's manuals), but in the end I decided to take the dimensions of the cut from my Sistema 1911 frame. The Essex slide I'd bought fit nicely on the Sistema, so I figured it would be a good idea to cut the new frame to match. I planned to cut the rails somewhat undersized to allow hand fitting and lapping for a tight fit.

To do the actual cut I chose to use a 1/16" thick slitting saw, and clamp the frame upright on my angle plate. Below are a couple of photos showing how I set up the frame for the initial cut. The tactical rail came in handy for a clamping spot; this area was much thicker than a standard 1911 dustcover. There are several ways to cut the rails, but I thought the slitting saw would be easiest to use and would minimize the chance for errors. With the saw being 1/16" thick I would have to make two passes to achieve the 3/32" width of the slot.

Here you can see me using the dial test indicator to make absolutely certain the frame is parallel with the spindle. A few taps with a light hammer lined it up nicely.

Before making the cut I painted the frame with layout fluid and used a dial indicator to position the slitting saw at the correct height to make the first cut. I checked the travel of the table first to be certain I would have enough room to cut the whole length of the rail. The mini-mill's travel was enough to do the job, but just barely. OK. Now to make the first cut.

I ran the slitting saw at about 700 RPM, used plenty of cutting fluid, and fed the table slowly. I advanced the saw into the piece about .010 at a time, until I reached the dimension I'd set. The saw did a beautiful job. It didn't have the least problem making the cut. After the first pass, I lowered the quill the rest of the way and made the second cut. Then I flipped the frame over and cut the other side. Here is how it looked after the cuts were complete.

While the frame was clamped upright to the angle plate, I took the opportunity to cut the barrel link relief slot in the locking lug area. This is just a short groove that gives the barrel link room to swing down. I don't have any photos of this process, but it wasn't difficult. This is not a critical cut in any way, you just don't want the barrel link to touch metal. I used a 1/8" endmill and just eyeballed this cut, comparing it to the existing cut on my Sistema frame. I took a couple passes and that was finished.

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