This project started with a simple frustration.
I use utility knives all the time in the shop — opening boxes, trimming prints, cutting filament, breaking down packaging — and I wanted something that felt solid, safe, and predictable, without relying on tiny springs, metal hardware, or complicated internals.
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That’s what led to SLUK: a fully 3D-printed, self-locking utility knife designed around simplicity, reliability, and everyday use.
What Makes SLUK Different
The defining feature of SLUK is right in the name: self-locking.
Instead of a traditional spring-loaded slider or button lock, SLUK uses geometry and friction to lock the blade carrier in position automatically. Once extended, it stays put. When retracted, it stays put. No extra parts, no tiny mechanisms, and nothing to wear out quickly.
It’s a very “3D-printing-native” solution — using shape, tolerance, and material behavior instead of hardware.
Designed for Standard Utility Blades
SLUK is designed around standard utility blades, which are inexpensive, widely available, and easy to replace. The blade is fully enclosed when retracted, and the body provides a comfortable grip without being bulky.
The goal wasn’t to reinvent the utility knife — just to make a clean, functional version that prints well and works reliably.
Printing and Assembly
This design is intentionally straightforward to print and assemble.
- Fully 3D printed
- No supports
- No metal hardware
- Simple press-fit assembly
PLA works well, and PETG or ASA are also good options if you want a bit more durability. As with most functional parts, decent wall thickness matters more than extreme infill.
The tolerances are forgiving, but like most sliding parts, good extrusion consistency helps.
Why I Made This
There are lots of utility knives out there — cheap ones, fancy ones, disposable ones. What I wanted was a printable tool that earns a permanent place in the shop, one that’s easy to understand, easy to maintain, and safe to toss in a drawer or toolbox.
SLUK is the result of that thinking: simple, solid, and designed to work the way you expect it to.
Give It a Try
If you print one and put it to use, I’d love to hear how it holds up for you. Feedback, tweaks, and edge cases are always welcome — that’s how these designs get better over time.
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