Last updated: March 2026

Polymer80 Glock 19 Jig Instructions for Beginners: My Step-by-Step Guide

If you’re holding a Polymer80 Glock 19 frame kit and feeling that mix of excitement and apprehension, I’ve been there. I’m Jake Morrison, and I’ve been building, testing, and perfecting these kits since before they were a mainstream project. In my shop in Tampa, I’ve personally overseen the completion of over 500 builds, from simple G19s to fully custom race guns. The single most critical phase that determines the success or failure of your build is the work you do in the jig. This isn’t just a tutorial; it’s the collective wisdom from seeing every possible mistake, so you don’t have to make them. Let’s get your foundation perfect.

Understanding Your Polymer80 Glock 19 Jig: It’s Not Just a Block of Plastic

Before you even think about drilling or milling, you need to understand what the jig is designed to do. The Polymer80 jig is a precision alignment tool. Its sole purpose is to guide your drill bits and your end mill to the exact locations required for your frame’s fire control group. A 0.5mm deviation can mean the difference between a smooth-running pistol and a paperweight. The jig consists of three main pieces: the main body that cradles the frame, and two side plates that clamp everything together with the provided screws. The most common version for the Glock 19 is the PF940C. Treat this tool with respect—it is the key to your build’s integrity.

Tools You Absolutely Need (And What You Don’t)

I see a lot of guys try to improvise. Sometimes it works. Often, it leads to a ruined frame. Here is the non-negotiable tool list, based on building hundreds of frames:

Power Drill (Corded Recommended): A variable-speed corded drill offers consistent torque. A weak cordless drill can bog down and create rough holes.
Polymer80 Drill Bit Set: Use the bits provided in the kit. They are specifically sized for the 3mm and 4mm pins. If you lost them, you can find replacements in our shop under tools.
Hand Drill Press or Drill Guide (CRITICAL): This is the #1 tool to prevent “walking” and angled holes. A simple $40 hand drill press from a hardware store will improve your accuracy tenfold. Do not freehand drill the pin holes.
Dremel Rotary Tool or Exacto Knife: For cleaning the recoil spring channel and tabs. A Dremel 8220 is my personal go-to.
End Mill Bit or Robust Router Bit: The provided end mill works, but a quality 1/4″ or 3/8″ single-flute router bit in a Dremel collet is more aggressive for the rail tabs.
Safety Gear: Safety glasses and a respirator or mask. You do not want to breathe in polymer dust.
Vise or Strong Clamp: To securely hold the jig assembly. Movement is the enemy.

For a complete kit with the right tools from the start, check out our builder bundles:

Step-by-Step: The Polymer80 Jig Procedure, No Steps Skipped

Phase 1: Preparation & Secure Clamping

1. Inspect and Assemble the Jig: Lay the Polymer80 frame into the main jig body. The rear of the frame should sit flush in the pocket. Place the two side plates on. Insert the four provided screws and tighten them evenly and firmly by hand. Do not use a power driver here—you can crack the jig. The frame should have zero wobble within the assembled jig.

2. Secure the Entire Assembly: Place the clamped jig into your vise or secure it to your workbench with C-clamps. It must not move, flex, or shift during any operation. I clamp mine directly to a heavy wooden bench. This step is where 20% of beginners fail before they even start drilling.

Phase 2: Drilling the Pin Holes – Precision is Everything

3. Identify the Holes: You have four holes to drill in the jig: the two 3mm holes (front locking block pin and rear rail module pin) and the two 4mm holes (trigger housing pin). The jig is clearly marked with “3mm” and “4mm.” Confirm you have the correct drill bit for each. The 3mm bit has a black ring, the 4mm bit has a silver ring.

4. The Drilling Technique: Insert the correct bit into your drill. If using a hand drill press, set the depth stop so the bit will penetrate completely through the jig and frame, but not plunge deeply into your work surface. Apply firm, steady pressure. Do not rush. Let the bit cut the polymer. Drill straight through one side, then flip the entire jig assembly over and complete the hole from the opposite side. This is the factory-recommended method and prevents tear-out on the exit side, ensuring clean holes. I drill all my 3mm holes first, then switch to the 4mm bit and repeat the process.

5. Deburr and Clean: After all holes are drilled, remove the frame from the jig. Use a small round file or the drill bit itself (by hand) to gently remove any polymer burrs from the inside of each hole. Blow out all debris with compressed air.

Phase 3: Milling the Rail Tabs & Recoil Spring Channel

6. Removing the Rail Tabs (The “Ears”): This is where you need control. The two large polymer tabs in the frame’s center section must be removed so the rear rail module can sit flush. Using your Dremel with the end mill or router bit, carefully mill the tabs down to the base line indicated on the frame. DO NOT mill below this line. Work in multiple light passes, checking fitment with the rear rail module frequently. The goal is for the metal rail to sit perfectly flush with the polymer shelf. I’ve seen more frames ruined by over-milling here than any other step.

7. Cleaning the Recoil Spring Channel: This is the channel in the front of the frame under the barrel. The polymer here is thin. Use a sanding drum or a small grinding stone in your Dremel. Go slow. The goal is to create a smooth, U-shaped channel so the recoil spring assembly can cycle freely. Shine a light down the channel—any ridge, lip, or polymer debris will cause a failure to return to battery. I spend at least 15 minutes on this step alone, finishing with 400-grit sandpaper by hand for a glass-smooth finish.

The 5 Most Common Polymer80 Glock 19 Jig Mistakes (And How to Avoid Them)

After seeing hundreds of builds, these errors are painfully predictable. Let’s make sure your build isn’t one of them.

Mistake #1: Freehand Drilling the Pin Holes. This almost guarantees misaligned holes. The result? Pins that won’t go in, or rails that are out of spec, causing binding and failure to fire. Solution: Use a $40 drill guide. It’s the best insurance you can buy.
Mistake #2: Over-Milling the Rail Tabs. Enthusiasm with the Dremel creates a low spot. The rear rail module then sits too low, causing catastrophic misalignment with the slide and barrel. Solution: Mill to the line, not past it. Test fit constantly.
Mistake #3: An Incomplete Recoil Spring Channel. A rough or shallow channel is the #1 cause of failure to go fully into battery. Solution: Use a small flashlight to inspect. The channel must be smooth and deep enough for the spring to compress fully without catching.
Mistake #4: Not Drilling from Both Sides. Drilling all the way through from one side often causes ugly blow-out on the exit side, which can interfere with pin seating. Solution: Always drill one side, flip, and complete the hole.
Mistake #5: Rushing and Skipping Test Fits. This is a precision project, not a race. Solution: After the jig work, perform a full test fit without the slide. Install the locking block and rear rail module with their pins. They should drop in and pin smoothly. Install the trigger mechanism. Everything should move freely. If there’s binding, stop and diagnose before assembling the slide.

Post-Jig Steps: Final Assembly and Function Check

With your jig work complete, you’re 70% of the way there. Now comes the assembly of the fire control group. Insert the trigger mechanism housing, the rear rail module, and the front locking block, securing them with the pins you drilled. They should fit with firm hand pressure using a punch—never force them with a hammer. If a pin won’t go, your holes are misaligned. After the lower parts kit is installed, perform a functions check. Then, move on to selecting your slide and barrel from our parts shop. A quality slide completion kit is just as important as your frame work.

Final Thoughts from the Bench

Building a Polymer80 Glock 19 is incredibly rewarding. That first smooth slide rack on a frame you finished yourself is a feeling you can’t buy. The difference between a problematic build and a flawless one lies in the patience and precision of the jig work. Take your time, respect the tools, and follow these steps. This isn’t just a hobby; it’s a craft. And if you need parts, tools, or advice, my team and I at the shop are here to help. Now, go build something.

Polymer80 Glock 19 Jig FAQ

My pin holes are slightly misaligned and the pins are tight. What should I do?

Do not force them. First, ensure any polymer burrs inside the holes are completely removed with a round file. If they’re still tight, use a set of pin gauges or the drill bit itself (by hand) to very gently and evenly ream the hole. Work from both sides. The goal is to remove thousandths of an inch, not to redrill. If the hole is visibly off-center, the frame may be out of spec and you should contact the manufacturer.

Can I use a drill press instead of the hand drill guide you recommend?

Yes, a full-sized drill press is excellent, provided you can securely clamp the jig assembly to the table at a perfect 90-degree angle. The challenge is the jig’s height; many drill presses don’t have enough throat depth. The hand drill guide is often more practical for this specific task. The core principle is eliminating hand-held drill wobble.

I over-milled one of the rear rail tabs. Is my Polymer80 frame ruined?

Not necessarily, but it’s a serious fix. Do not attempt to build on it. The rear rail module must sit at an exact height. You can sometimes use a small shim (like brass shim stock) under the rail to bring it back to the correct plane. This requires precise measurement. For most beginners, it’s a lesson learned, and a new frame is the most reliable solution. This is why we stress “mill to the line.”

What’s the best way to smooth the recoil spring channel after using the Dremel?

After rough shaping with the Dremel, I switch to hand sanding. Wrap 400-grit sandpaper around a pen, a dowel, or the shaft of a drill bit that fits the channel. Polish in a back-and-forth motion until the polymer feels completely smooth to the touch. Finish with a final pass of fine steel wool. The spring should glide without any catching.

Where can I get replacement jigs or specific tools if I lose mine?

Replacement jigs, drill bits, and specialized tools like the hand drill guide are available through our online shop. We stock them specifically because these are the parts builders most commonly need to replace. Using the correct tool for the job is the foundation of a successful build.