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We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, New Jersey, New York, Pennsylvania, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.

How to Complete an 80% 1911 Frame

Posted by AR-15LowerReceivers.com on Jul 9th 2020

How to Complete an 80% 1911 Frame

If you've decided to build your new 1911 from scratch using an 80% frame, you're in the right place. This instructional guide provides detailed steps and photos for cutting and drilling the frame, making it functional and ready for parts installation. We're using Stealth Arms' frames -- these instructions are applicable for both a Government (5") and Commander (4.25") frame -- and their accompanying Phantom 1911 Jig

To assist with the install steps, a .PDF version of the instructions are available.

The 1911 Jig: What's Included

The Phantom Jig comes with all the parts you need to complete your frame, including machining oil for lubricating the side plates for the cutting car. 

  • (1) Right-Hand Side Plate
  • (1) Left-Hand Side Plate
  • (1) M5 Cap Screw for Plates
  • (1) Cutting Car
  • (1) Adjustment Knob
  • (1) Spacer Block
  • (1) Rail Cutter Blade
  • (1) Barrel Seat Blade
  • (2) 10-32 Set Screws
  • (1) 0.157" Dowel Pin
  • (1) 0.201" Dowel Pin
  • (1) #35 Drill Bit (0.11" dia.)
  • (1) #22 Drill Bit (0.157" dia.)
  • (1) 5/32" Allen Wrench
  • (1) 3/32" Allen Wrench
  • (1) 1-oz. Bottle of Oil

Tools You'll Need

There are just a few basic tools you need to complete your frame, in addition to the tools included with your jig:

  • 5" Vise
  • Drill Press
  • Permanent Marker
  • Eye and Ear Pro

Attempting to drill the frame's pin holes with an electric drill is not recommended. A drill press is required to ensure both the hammer and sear pin holes are drilled perfectly vertical through the frame, otherwise, your parts kit won't install correctly.

Machining the Frame

Step 1: Secure the frame and jig

To get started, locate the two dowel pins, the M5 hex-head bolt, and its accompanying Allen key. The dowel pins will seat within two of the holes on both the left and right side plates, traveling through the frame itself to hold it in the correct position for cutting:

Tighten the hex-head bolt so the plates and frame are secured. Do not over-tighten this bolt or the side plates could flex and warp, ruining your frame cuts and drilling alignment. The vise will be primarily responsible for keeping the assembly secure.

Step 2: Secure Jig in Vise Horizontally

IMPORTANT: You must insert the rectangular aluminum spacer block inside the cutting slot of the side plate that is to be tightened inside the jig. The spacer block prevents the side plate from warping when the jig is tightened inside the vise. Only clamp the side plate opposite of the one you're drilling through. We're starting with the pin holes on the right side of the frame, so the block should be inserted in the left-hand plate first:

To ensure the pin holes are perfectly aligned, only drill through one half of the frame, then un-seat the jig from the vise, flip it over, and re-tighten the assembly with the spacer block inserted in the opposite side plate. 

Do not attempt to complete each pin hole by drilling entirely through the frame to the opposite side. Do not attempt this step with a handheld drill.

Step 3: Set Up Cutting Car for Slide Rails

Although the carbide blades are installed in the cutting car, they cannot be used for cutting the slide rails without "zeroing" the blades first. Loosen the Allen-head set screw securing the blade in the car, first:

Once loosened, press the carbide blade into the cutting car so the tip of the blade is barely protruding from the guide boss, as shown above. Re-tighten the set screw. Ensure the blade is pointing in the direction of the arrow on the top-front of the cutting car:

Next, thread the adjustment knob into the threaded hole above the rail cutter. Tighten the grip handle to the car immediately behind the adjustment knob.

Measuring Your Cutting Depth

Before cutting the slide rails, it's important to understand how to properly measure your cutting depth. Otherwise, you might cut the frame too shallow or, worse, too deep. With the adjustment knob tightened, align it with the tick mark closest to the white dot on the knob:

The tick mark will be your starting cutting depth. Mark this tick mark with a permanent marker. As you cut the frame, you'll increase your cutting depth by rotating the adjustment knob clockwise by one tick mark at a time. You must rotate the adjustment knob exactly 19 notches, or 1.9 rotations. That means you'll make one full rotation back to your starting tick mark, followed by a second rotation that ends at the tick mark immediately before the marked tick mark. If you want to verify the correct depth has been achieved on each slide rail, you may measure from the face of the frame to the bottom of the cut itself. The final depth of each slide rail should be 0.061":

Step 4: Cut the Slide Rails

Before cutting, apply some of the provided lubricating oil to the face of the jig, and inside the cutting slot. Place the guide boss containing the carbide blade inside the slot. When cutting the frame, only apply moderate pressure to the cutting car in the direction facing away from you. When pulling the cutting car back toward you, partially lift the car with the grip handle so the backside of carbide blade is not dragging along the frame.

At the starting tick mark, cut the frame in the forward direction until no more resistance is felt against the blade. Then turn the adjustment knob one tick mark, clockwise. Repeat cutting until no friction is felt, and continue this procedure until you've made 1.9 rotations. Once one side is complete, remove the jig and frame from the vise, flip it over, ensure the spacer block is resting in the opposite cutting slot, and re-tighten the assembly. Repeat step 3 to "zero out" the carbide blade, and cut the other slide rail.

Step 5: Reconfigure Jig and Frame for Barrel Seat

To cut the barrel seat, the other guide boss and carbide blade will be used on the cutting car. Before we get to that, we need to reconfigure the frame's placement within the jig. Remove the jig and frame from your vise, and remove the Allen-head hex bolt and dowel pins from the frame and jig:

Reinsert both dowel pins in the two holes above the slide rail cutting slots. The 0.201" dowel pin should be placed forward of the slot, and the 0.157" pin should be placed at the hole near the rear of the plate, above the slot. The pins will go through the same holes on the frame, immediately above the trigger well and at the tip of the dovetail.

Step 6: Set Up and "Zero" Cutting Car for Barrel Seat

Un-thread the adjustment knob and grip handle from their respective positions on the cutting car, and re-thread both on the left-hand side of the car:

Repeat step 3 for zeroing the barrel seat's carbide blade: Loosen the set screw, allow the blade to barely protrude from its guide boss, and align the white dot on the adjustment knob with the closest tick mark. Mark that tick mark as the starting position.

IMPORTANT: It's been reported that some builders are accidentally cutting the barrel seat too deep. There are two flat tabs on either side of the barrel seat blade that indicate when you should stop cutting: 

If the corners of these two tabs are cutting into the frame when cutting the barrel seat, stop cutting. The cutter's set screw may also loosen while you adjust your cutting depth. To prevent this from happening, verify the set screw remains tight throughout the cutting procedure by giving it a slight turn with the appropriate Allen key.

Step 7: Cut the Barrel Seat

Secure the frame and jig assembly vertically in your vise, with the barrel end of the frame facing toward you. Apply lubricant to the top of the frame and jig:

In the same fashion as the slide rails, cut the barrel seat by applying moderate pressure to the cutting car via the grip handle as you push the assembly away from you. Lift the car slightly to prevent the blade from dragging on the frame as you pull it back, and continue cutting at the starting tick mark until no friction is felt. Then, increase the cutting depth by rotating the adjustment knob to the next tick mark and repeat these cutting procedures until you've made 2.4 rotations of the adjustment knob. If you're verifying the measurement, the final cutting depth of the barrel seat should measure 0.077" from the top of the frame:

Your 80% 1911 Frame is Complete

With the barrel seat cut, your 1911 frame is complete! You can now install either the parts kit that came with your frame (if you purchased a complete build kit), or you can order a quality parts kit that includes everything you need.

If you prefer to buy custom components piecemeal, you'll need the following to assemble your pistol:

  • Slide
  • Slide Stop
  • Barrel, Link, Pin, Barrel bushings
  • Adjustable Trigger
  • Grips
  • Grip Safety
  • Grip Screws & Bushing
  • Hammer
  • Hammer Strut
  • Sear
  • Mainspring Housing
  • 11-Piece Pin Set
  • 7-Piece Spring Set
  • Magazine Catch
  • Firing Pin Stop
  • Extractor
  • Thumb Safety
  • Disconnector
  • Plunger Tube
  • Ejector
  • Recoil Guide
  • Magazine

DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At 80-lower.com, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.

We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.