Safety Knife PRO ● Auto-Retract (PiP mechanism)
Print Profile(9)
Bill of Materials
- Standard Trapezoidal Utility Blade x 1: https://www.amazon.ca/dp/B0CNXMD7ZM?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1
Description
Safety Knife PRO V1.5 | Auto-Retract & Print-in-Place core mechanism 🔪
Introducing the Safety Knife PRO, a fully 3D printable utility cutter designed for safety and reliability. The blade automatically retracts the moment you release the slider, significantly minimizing the risk of injury.
The core mechanism features a Print-in-Place design, making the assembly incredibly fast, satisfying, and accessible to everyone.
UPDATE 2025/12/18 📢 | Better, Stronger, Safer! | V1.5
I've refined the design based on your feedback to improve both safety and daily usability.
What’s new?
- New selection dial with 3 depth levels and an integrated Safe Lock.
- Smoother sliding action thanks to optimized internal tolerances.
- Stronger blade holder to ensure better long-term reliability.
- Upped spring tension for a snappier and more secure retraction.
- Light frame reinforcement for a slightly more solid feel.
Why this update?
The new Safe Lock position on the dial directly addresses safety concerns for pocket carry, while the three selectable levels give you the perfect amount of edge for any task.
Key Features
- ⚙️ Selection & Lock System: Features a new dial with 3 selectable blade lengths and a dedicated Safe Lock position for secure carry.
- 🛡️ Enhanced Auto-Retraction: Increased spring tension ensures the blade snaps back instantly and reliably after use.
- 🧩 Print-in-Place Mechanism: The internal slider and complex moving parts are printed as a single unit—no assembly required.
- 💪 Improved Durable Design: Features a reinforced frame and blade holder, with a spring optimized for PETG to ensure long-lasting reliability.
- 👁️ Visible Mechanics: A transparent print profile is provided to showcase the internal workings and the new locking dial in action.
Hardware Required
- 5x M3x10 Self-Tapping Screws.
- 1x Standard Trapezoidal Utility Blade (Amazon link).
- 1x Short piece of 1.75mm filament (approx. 6-7mm long).
Print Settings
- Spring: PETG is highly recommended. While PLA works, PETG offers superior elasticity and durability for the spring mechanism.
- For the transparent effect, I used DRIED PETG Translucent Clear and downloaded this profile: Clear as glass PETG from Just say no to poop.
- My associated profile is basically a copy plus some modifications and paintings.
Assembly
Break Free: Gently move the slider back and forth to break the Print-in-Place supports and ensure smooth movement.
Linkage: Cut a small piece of 1.75mm filament (~6mm) and insert it as a pin to link the mechanism arm to the lever.
Case Assembly: Place the mechanism and the spring into the bottom case, then close it with the top cover using the M3 screws.
Blade Installation: Insert the small locking piece as shown, then slide the blade into the holder. Ensure it fits securely but is not too tight.
How to change the blade ?
How to adjust the blade?
Credits & Acknowledgments
- Spring design made using the Parametric Flat Spring from Orel_Zolo.
- Transparent settings adapted from Clear as glass PETG from Just say no to poop.
Feel free to reach out if you have any questions. Enjoy your making journey! 🛠️💬
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If you like this model, a boost is always appreciated ! 😊 Thank you very much !
If you really like what I do, you can also buy me a beer🍺! Happy printing!
License
You may create derivative works based on this object, provided that all such derivative works are published exclusively on the MakerWorld platform and include proper attribution to the original creator. You may not share, upload, host, distribute, or publish this object—or any derivative work of this object—on any other digital platform, marketplace, or distribution channel. Commercial use of this object and any derivative works is strictly prohibited. This includes, but is not limited to, selling, renting, sublicensing, or using the object in any context in which you receive monetary compensation or other financial benefits.
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