Finally got the Tactical Machining 1911 Jig in the mail so I threw the 80% in there and got ready to cut the slide rails.
This is probably the hardest cut so I figured I’d do it first in case I messed up. Disclaimer again.
You’ll also need the bits, drill press, sliding vise, calipers, & Dykem I mentioned in Part 2. Tighten everything down and make sure you can smoothly move the main axis of the sliding vise.
Double check your resources and measure your slide with a good caliper. For me, I am going to cut down .105″ from the top, and go .05″ deep. The 3/32″ keyseat cutter comes out to be .09375″ while the slide’s thickness is .12″, so there will be some filing. The square file in the file set tapers from around .09″ to .011″ so it should be good to go.
Dykem & Marking
Before you put the 80% into the jig, paint some Dykem on it. I got excited and put it into the jig first before painting so you’ll see blue all over the jig in the pictures. I would put it thicker next time too. Do it in some well-ventilated place and let it dry. Measure off .105″ on your caliper and lock it. I put the edge of the caliper on the top of the paperweight and let the sharp edge cut into the Dykem. Perfect!
Put the jig with the 80% into your vise. Make sure you’ll have enough space to move everything around. Last thing you want to do is reset halfway through when your jig hits the drill press. I’m definitely guilty…
Get into Position
The TM jig fits well but you cannot expect it to hold the 80% perfectly level. Use your level and if needed, move the jig around.
Move everything closer to each other so you can change the height of the bit. I prefer to move the bit up and down rather than the platform.
Measure twice…or ten times, then get ready to cut. I went for something around .04″ deep for the first cut. Make sure you hold the jig steady and not yank it…you can see my deeper cut about half an inch from the right side. Then just go nice and slow while holding the line you cut into the Dykem with the caliper.
Watch out when you near the end since I had the bit jump. Nothing a little filing can’t fix!
I measured and everything was good, with just some variations from .04″ to .045,” so I went ahead with a second pass to get the proper end depth.
I setup the other side and did the same thing.
Keep the jig as is so you can do the barrel seating cut next. You’ll have plenty of time to file and lap the slide to fit the frame.
Part 1: Intro (Finding the 80%)
Part 5: Cutting the Slide Rail
Part 6: Barrel Seating
Part 7: Hammer & Sear Pin Holes
8 Leave a Reply
I was going over your article about building an 80% M1911 and, in part 4, I think, you note certain measurements as below. It would seem you mean that 0.09375 < 0.12, not 0.012 as stated. I am wrong about that?
The 3/32″ keyseat cutter comes out to be .09375″ while the slide’s thickness is .012″, so there will be some filing.
Hi Bruce, I believe you are correct. Thanks for catching the mistake!
What did you use to clamp the vise to the drill press?
I used a couple bolts/nuts/washers I had lying around and aligned the vise to the base of the drill press the best I could.
what rpm/speed did you set your press at? also how long to just cut the rails on the press(not file too)? did your bit stay sharp?
thanks, thats a clean build
Thanks! I set my drill press to the fastest rpm. The actual cutting was very quick, probably a few minutes each side. I spent a lot longer just double-checking the positioning of everything. I also found no problem with the bit staying sharp for a couple passes on each side.
Where did you get specs for cutting the rails?
I got them from my Kuhnhausen book, but there's this link (choose 1911-A1 blueprints).
But the best is to start there and measure your actual slide since that is what has to fit onto the receiver.