DualShift v1.3-Auto OTF switchblade- Get custom cover!

fidget/utility. Ultra satisfying work!
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updated January 14, 2025

Description

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PRECAUTION: You can use it as a toy, if you just dont mount real blade.  But if you want, you can screw on a real trapezoidal blade, but: BE REALLY CAREFUL! Trapezoidal utility blades are really sharp. If you do this- don't give the model to your kids. Knife haven't any redundant safety mechanisms, and it can expand spontaneously. The spring is not tensioned, but we have also gravity, shakes and other environmental cases. Remember, that you are using them on your own responsibility.

 

 


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If you print this model, I’d love to see your "Make"! Your feedback is incredibly important to me, especially since this model involves a complex mechanism that I want to ensure works properly across different printers.

💡 As a thank-you for your support, I’m offering something special:
I’ll create a custom cover or housing variant with your graphic(svg) or text of choice! This could be your logo, a personal message, or any design you’d like.

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Screws are not absolutely necessary to assemble the model and check if it works.

 

Knife have only 73,5mm long, and are only 12,5mm longer than trapezoidal blade itself. 

 

Made in Poland. 

 

I spent a lot of time and filament designing this model. I was curious if it was possible to build a knife on a 3D printer that would work like the OTF double action spring knives. My mechanism offers incredibly smooth operation, converting 8mm move of trigger to 55mm move of blade. The trigger-to-blade-move ratio is same or better than in standard OTF knives. 

 

Pre-printing tips:

  • Calibrate your printer before print. It's really exacting model. Dimensions and clearances were created carefully and costs me a lot of hours and filament. Model can be printed also on budget printers, but good working. My cheap printer(Sidewinder X4) can handle this :)
  • I suggest print spring and latches with PET-G, becouse PLA have really big creep. Main spring will still work some time, becouse it's working only when knife is expanding/slide apart. But one of latches are always on tense, so after few hours its creep and knife can't lock blade. Other elements can be print with PLA.
  • Of course, you can print whole model with from PLA itself and it will also work - you will be able to check the operation of the mechanism.
  • If you havent other filaments than PLA, you can just set trigger in “middle” with unlocked blade if you are not using them. This will make the latches loose and avoid creep. 
  • Use “slick” filaments, especially in the housing(bottom part), blade frame and slider.. If you have only matte, you will have to use silicone oil(not silicone grease) to make knife run smoothly. The operation of this mechanism is based largely on inertia and must move very easily. 
  • print lid, pin, spring and latches(trust me- latches are important) upside down
  • print clip standing on its side
  • other elements print “as is”
  • You need two latches. The remaining parts one each
  • Use supports(tree will be best) on each model.  Its used for fill screw heads and nuts, and also for clip. If they are not necessary in some part the slicer will not add them. Thats only suggestion. Supports are necessary only for clip. 
  • I recommend 100% infill and 0.2mm standard profile.

 

Generally i suggest printing in 4 sessions:

  • Housing and lid(upside down) with PLA in main color
  • Clip, blade frame, blade block, pin, slider with with PLA in accent color
  • 2 springs-main and spare :) with PET-G(or, better- with PC). Dont print more than 2 in one session.
  • 2 or 4(spare) pcs of latches with PET-G. If you print more at once(or with spring) - they may delaminate due to too long time between layers.

 

Selecting the spring

You see in project a lot of springs. First you shall try 8x2.1mm for PLA, or 7x2.5mm for PET-G/PC. If they don't work properly- try others. If your mechanism work very lightly, you can try *x1.9mm. Generally, too strong spring can damage latches, so be careful. If knife cant unlock- don't push too hard. Change spring to lighter. 

First digit is number of bends, and second is thickness in mm.

 

Selecting the latch

I recommend 1mm for PLA and 1.2mm for other materials, like PET-G, PC. 

 

Post-printing tips:

 

  • Use the screw to remove support from screw head's pockets
  • Check if the spring after printing has no defects. If it has - it will break very quickly, so reprint them
  • Use deburrer or sandpaper(or your nail XD)  before assembly, and make sure that nothing is jammed or offers any resistance and that the surfaces are smooth.
  • Insert pin into frame, and slide it inside housing tightly a dozen times until it starts moving lightly

 

Assembly tips:

 

If, despite the warning, you still want to screw real blade, you will need also:

  • 3xM2x4mm w/ cylindrical head screws(1.3mm head height) for blade
  • 4xM2x10mm w/ cylindrical head screws for housing assembly
  • 7x M2 nut

If you just want fidget toy- you can insert just frame, or screw in printed blade imiter(included). If you are not installing a real blade, you can use a bit of glue instead of screws.

Usage

  • The mechanism can require a break-in period to start operating smoothly. It can be even several dozen cycles. 
  • Keep you fingers away blade pocket :)
  • The spring and latches probably have a limited lifespan. If you'll be playing often - have spares.
  • If the blade does not lock, simply slide it out or in using the slider at the back
  • It knife cant unlock- don't push too hard. Use lighter spring.

 

Ending

If you have any problems- write to me before leaving a negative comment. I've come across a lot of model problems in process of drawing and testing them, that can be easily fixed. And if not: Project is easy customizable, and I can prepare parts with slightly changed dimensions/clearances especially for your request. More elastic spring for other materials? Larger clearances? no problem. Just PM Me. 

I need feedback because I want the project to be able to work on any printer after it is made. Feel free to PM me. 

 

Look on my another knife project, OTF gravity knife, G-Shift:

https://www.printables.com/model/1129013-g-shift-v13-gravity-knife-get-your-custom-cover

FAQ(no one asked me these questions, I asked them myself)

Q: My model cannot unfold on its own, its stopping before reaching end position due to friction

A: Try to use stronger spring; try to use more slick filament for bottom housing, blade frame, and slider. If the above steps do not help, PM me or try to scale in Z axis bottom part of housing- make it little bit higher. Dont forget to scale also latches.

 

Q: My model cant unfold, becouse it can't tense latch(latch spins instead of unfold)

A: Did you printed latches upside down? If not- try. It z-offset if your printer is too low, it create some small “brim” around latch, and it can jam with blade frame. Also try to use  weaker spring. 

 

Q: My latches are got delaminated in try of expand knife. What i did wrong?

A: If you printing them with PET-G- try to lower temperature of printing for 10-15degrees.

 

Changelog:

 

v1.3(S only)

new latches shape

longer slide

new springs

wider spring windows

new trigger

better work

 

21122024

added S version

 

v1.2 18122024

shallower latch cuts

clearance between latch and bottom

more durable arched spring mount

 

v1.1 16122024

Deeper latch cuts

More springs, removed 2.8 and 2.9 spring

More “meat” for blade screws- now you need flad cylindrical heads, and 4mm thread

Smaller latch windows

 

v1.0

initial release

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