[DIY] Folding Utility Knife FOUTIK V1.2 - 3D Print

After reviewing a few simple utility knife / box cutter 3D printed models and not finding what I was looking for, I decided to design a folding knife that is easy to print, cheap yet sturdy, safe to handle, and comfortable to use for light construction / demolition tasks.

Meet FOUTIK (FOlding UTI-lity Knife, how lazy ðŸ˜…)

All handling operations can be performed while wearing thin gloves: open, close, blade change.

The (messy) Fusion 360 CAD model, STEP and 3 MF files are all on Github and Makerworld

  Update    updated all files to V1.2 - increased quality and printability for non-Bambu filaments, integrated supports, 2mm wider body

Feel free to copy / remix / publish / whatever. 

Happy printing to all !

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Design

Available in 2 versions, a Basic one and one with glued-on Inlays:

The Basic design consists in 2 simple parts:

The knife stays open or closed thanks to a flexible lock finger that catches either the blade head's stay-open groove or the stay-closed groove:

 The blade is held in place by a flexible finger:

To switch in the CAD model between the Basic and Inlays versions, just Suppress / Unsuppress the corresponding features.

To add text / drawings to inlays:

  • either emboss them in the slicer
  • or in Fusion 360: Create a sketch on each inlay face with your text / drawings, Extrude them as New Body, then Combine Cut them out of the inlay body.

 

 

Printing

Settings for a 0.4mm nozzle on Bambu P1S, PLA or ABS:

  • 0.95 flow, 0.2 layer height, 0.45 width
  • 2 walls, 2 top & bottom layers
  • concentric solid infill 
  • 100% concentric sparse infill
  • no 'Infill Combination' 
  • no support (for cleaner hole in basic version, can enable: tree auto, organic, 33° angle, build plate only)
  • 5mm outer brim

 

For the Inlays version you'll first want to change the CAD model with your own text / logos (see Design chapter above), or just emboss them in the slicer itself. To change the color of any embedded text and logos, make sure to Split to Parts the 2 inlay objects first. 


 

Assembly 

For the best result, it is very important to let the printed parts FULLY cool down before starting the assembly process. Even when cool to the touch parts of the melted filament will still be in a partial plastic state for several minutes after cooling down to ambient.

If not fully solid, when snapping loose the fingers, they will acquire a slight but permanent deformation with lower elastic modulus. Waiting an additional ~30' after cool down will help ensure they remain straight and stiff, satisfyingly snapping back into place when using the knife.

Step 1 - remove the brim

Removing the brim can leave behind a white line. A useful trick is to scrub it away with a plastic blade scraper or a dull chisel: 

 

Step 2 - remove the built-in supports

Remove the body sides' support by first cutting the little tabs connecting the support to the body, then break it away:

Remove the head latch's support by cutting the little tabs then break it away:

Finally, cut the little tabs around the blade finger, at least the ones that are easiy accessible: 

 

Step 3 - break loose the fingers

Using a large screwdriver blade or a chisel, gently pry apart each finger by rotating the blade, until it separates. Should hear a sharp sound when that happens (requires fully cooled down parts).

 

Step 4 - glue the inlays on (optional)



Handling

Opening the knife takes 2 hands. With one hand pull on the lever ears to disengage its lock on the head: catch the lever ears between the thumb and the middle finger while pushing on the body with the index finger. Then with the other hand pull on the head ears to rotate the head open.

Closing the knife takes just 1 hand. Simply pull on the lever ears and push on the head to rotate and close it.


 

To change the blade, pull on the blade lever.

Note that the blade can be set in an extended position when deeper cuts are needed: 

 

And now not only can I afford losing a box cutter every day, but they also serve as personalized gifts / memories for other construction crew members, thanks to the inlays. Example: "Glad you're leaving, Tom !". Sweet... 😅


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