Want to learn lock picking… or just enjoy a super satisfying mechanical fidget?

This Lock Picking Trainer combines realistic feedback, customisable difficulty, and a fun tactile mechanism into one print.

🧠 What This Is

A functional lock-picking trainer + fidget toy designed to simulate the feel of pin-tumbler locks.

Perfect for:

• Learning the basics of lock picking
• Practicing tension and pin control
• Or just enjoying a fun, mechanical fidget toy

✨ Key Features

• 🔧 Realistic Pin Mechanism – Simulates pin stacks for authentic feedback and realistic picking
• 🎚️ Adjustable Difficulty – Swap springs to change resistance & feel, change pin number and bitting, and trial more difficult pin geometry
• 🧩 Modular Design – Easy to assemble, modify, and experiment
• 🎮 Fidget-Friendly – Satisfying tactile experience to keep hands occupied while watching TV or other mental tasks
• 🖨️ Fully 3D Printable – Optional metal spring

⚙️ Spring Options (Important!)

You have two options:

Option 1 – DIY Spring using PLA

• Wrap filament around a pen while heating it (eg in hot water or with a hair dryer)
• Gives a softer, more forgiving feel
• Can adjust length or rate of wrapping as required

Option 2 – Compression Spring

• Use 12mm diameter compression springs - 25mm length recommended but different lengths can be used to create more or less pushing force on the pins.
• Provides stronger, more realistic resistance
• Better for advanced practice

⚙️ Print Settings

• Layer Height: 0.24mm for the plug/body/lid, 0.08mm for the pins (better to reduce the tactile feedback from layer lines)
• Infill: 7%
• Supports: Not required
• Material: PLA (PETG if you want more durability)

💡 Smooth prints = better tactile feedback

🧩 Assembly Overview

• Print both plates
• I recommend that you start by only using 1 pin stack, but as you gain confidence you can fill all 4
• Place the plug into the body, then insert a key pin (the rounded tip pins) with the rounded end downwards into the hole
• Follow this with a driver pin - I recommend starting with the smooth pins - serrated and spool pins are more challenging
• Add a spring on top, compress it, then slide the cover over the top so that the spring can't escape

🔐 How to Use

This trainer is designed to simulate the feel of a real pin-tumbler lock using just your fingers.

🟢 Step 1 – Apply Tension

Use one hand to apply light rotational pressure to the plug.

• You want the plug to slightly turn
• This creates resistance against the pins (just like a real lock)

🟢 Step 2 – Lift a Pin

With your other hand, use your finger to push up a key pin.

Your goal:
👉 Raise the pin until the gap between the key pin and driver pin aligns with the plug edge
👉 This point is called the shear line

✅ With only 1 pin, the lock should open easily once aligned

🟢 Step 3 – Add More Pins

Now increase the difficulty by adding more pin stacks.

• Use different key pin heights
• This simulates real lock variation

🟢 Step 4 – Find the Binding Pin

When tension is applied:
👉 Usually one pin will feel harder to push (this is the binding pin)

• Push this pin first
• Lift it carefully until you feel a slight movement or “set”

🟢 Step 5 – Repeat the Process

After setting one pin:

• Another pin will become the new binding pin
• Repeat the process

👉 Continue until all pins are set and the lock opens

🔥 Advanced Practice

Once comfortable with standard pins, try:

• 🌀 Spool Pins
• 🔩 Serrated Pins

These introduce more complex feedback:

• Spool pins can cause counter-rotation
• You’ll feel the plug rotate backwards slightly before setting
• The pin will fall into a “false set” when the narrow part of the spool is at the shear line

👉 This mimics real-world lock picking challenges

💡 Tips

• Use light tension — too much makes pins harder to set
• Go slowly and feel for feedback
• Try different springs for different difficulty levels

🎨 Tips for Best Experience

• Sand/lightly clean pin channels or pins if needed
• Try different spring strengths
• Change the bitting (size and order of the key pins), and try mixing in spool or serrated driver pins for added challenge
• Get someone else to fill out the lock so you don't know what you're facing