Why 3D-Printed Lockpicks are Unreliable

Lockpicking is a niche skill in most countries, and commercial pick sets are often restricted or require a license to purchase. In places where they're not available at all, some hobbyists use 3D printing to make their own. This post documents that approach. I printed a set of lockpicks and tension tools, then tested them against a standard pin-tumbler lock to see whether printed plastic can actually replace steel.

The tools

The set includes three tension wrenches, three rakes, two comb keys, and two bump keys. All were printed in PLA+ using a cheap printer (Easythread X1), no resin or specialty filament. I also attempted single pin picks, but after several failed prints (too thin, snapped under light tension) I shifted the project toward bypass-style tools instead, which held up better at this scale.

Testing

Step 01 : Preparation

Straight off the printer, the tools had rough edges and leftover strands, typical of a budget FDM printer with inconsistent extrusion and low print resolution. Before any testing, I needed surfaces that wouldn't snag or add friction inside the lock. I used a heated knife to melt down rough spots, then sanded the surface smooth. This removed excess plastic and softened sharp edges without changing the tool's dimensions.

Step 02 : Fit Test

Once the tools were cleaned, I tried inserting each one into the lock for a test. Most wouldn't fit. The printed thickness was over 0.8mm too wide for the keyway, even after the first cleanup pass in Step 1. To fix this, I sanded them down further to bring the width closer to spec. Most of the tools broke during this process, the thinner cross-section couldn't handle the sanding pressure on top of PLA+'s natural brittleness. Three tools survived: one rake, one tension wrench, and one comb key. Everything else failed before testing even started.

Step 03 : Testing the Comb Key

Since comb keys are mainly used on padlocks, I used a padlock I already train on regularly. After several attempts, the front half kept twisting instead of turning the plug. It couldn't hold up under rotational torque, the same force a real key uses to open the lock. The thin comb section flexed instead of staying rigid, which meant it couldn't transfer enough force to actually turn the cylinder. Result: Failed. The design itself may work, but PLA+ can't hold the shape under the torque this tool needs.

Step 04: Testing the Tension Wrench and Rake

With the comb key ruled out, I moved to the tension wrench and rake, tested on a door lock this time instead of the padlock.

The printed tension wrench broke immediately after I applied some tension, so I replaced it with a DIY tension tool made from a piece of a car windshield wiper, thin, flexible steel that could actually hold up under pressure.

With that in place, I tested the printed rake carefully. It held for a few attempts, but the wave pattern gradually wore down from repeated contact with the pins. Once the shape wore away, it couldn't set the pins anymore.

Result: Failed. The tension wrench broke on first real use. The rake wore down and lost its shape before it could finish the job, PLA+ can't take repeated mechanical stress at this scale.

Test Outcomes

The tension wrench broke on first use, it couldn't hold rigid shape under rotational torque. The rake worked briefly, but its wave pattern wore smooth from repeated pin contact and stopped setting pins. The comb key failed, the front half twisted instead of turning the plug. The bump keys broke before testing even started, too thin to survive post-print sanding. Across the full set, every failure traced back to the same problem: PLA+ deforms or breaks under the pressure lockpicking requires

Disclosure

This test used a 3D-printed kit made with a cheap printer with PLA+. A better filament or a printer with a more precise nozzle could produce stronger, tighter-tolerance parts than what I tested here. Even so, this specific test failed completely. That doesn't mean 3D-printed lockpicks are unreliable across the board, it means this exact setup was. Other tools built the same way, like 7-pin tubular picks or disk detainer pick tools, might hold up better. I didn't attempt either here, and wouldn't try them in PLA+ either.

Tools

• Easythread X1 3D Printer
• PLA+ Filament
• 3D-Printed Lockpick
• Standard Pin-Tumbler Padlock
• Standard 5 Pin Door Lock

Conclusion

PLA+ printed on a budget printer wasn't strong enough to function as a lockpick set. Every tool that reached real testing failed under torque, friction, or basic fit tolerance. Filament quality likely matters more than the printer itself.

Where legal restrictions block access to commercial tools, improvised metal parts, like the DIY tension wrench made from a car wiper, held up better than anything printed in this test.