3D Printed Fidget Knife Snaps Back And Forth All Day Long

Fidget toys all have a satisfying mechanical action to engage with, and [uhltimate]’s OTF (out the front) “fidget knife” model provides that in spades. The model snaps open and closed thanks to a clever arrangement of springs and latches contained in only three printed pieces.

Here’s how it works: at rest, the mock blade (orange in the image above) is latched in the closed position. As one presses the slider forward, the bottom spring begins to pull up against the blade until it moves far enough to release the latch. When the latch is released, the tension built up in the spring propels the blade outward where it again latches in the open position. Retraction is the same essential process, just in the opposite direction (and using a latch on the opposite side of the blade, which faces the other direction.)

As you may imagine, effective operation depends on the material. The model is designed to be printed in PLA, but [uhltimate] also provides a part variation with a stiffer spring for those who find that basic model isn’t quite up to the task for whatever reason. Smooth surfaces are also helpful for hitch-free operation, but lubrication shouldn’t be necessary.

If this sort of thing is up your alley, don’t miss the satisfying snap action of this 3D printed toggle mechanism, either!

31 thoughts on “3D Printed Fidget Knife Snaps Back And Forth All Day Long

      1. Hi Henry, you are correct in stating that this 3D printed mechanism is, in fact, not prohibited by English law. However, what seems to have escaped your attention is the invention of a little known cultural mechanism: humor. You see, the original commenter is poking fun at the UK’s knife laws which are stricter than most countries by saying that even a plastic toy barely resembling a knife’s action is illegal there. This is a joke because of how preposterous and exaggerated past reality it is. No one believes the original commenter actually believes this. Well, almost no one. I hope this has been helpful to you and will aid you in identifying humor when you come across it in the future.

        1. Thing is…. is it tho?
          Flick knives are illegal and so are “disguised knives”
          It’s designed to look like a knife, it’s just not that pointy, unless stabbed in the eye with it – which would then make it an offensive weapon.


          Now feel free to throw yourself at the mercy of the court and the UK justice system that believes a butter knife is an offensive weapon but a screwdriver cannot possibly be.

          And actually yes, depending on the circumstances it may be enough to get you arrested, but one would hope not enough to get you prosecuted, which are two entirely different things.

          1. But a butter knife absolutely is an offensive weapon if you put the effort in and occasionally a screwdriver, so your buttery screws might still get you a night in the clink, checkmate humour!!

      2. Not just for owning it, no, but flicking it open and closed in a public place and causing distress/fear, or bring it into a school, quite likely would.

        Whether you’d get charged is another issue. But you could very easily get arrested.

    1. Indeed, here in MD it would be “constructive intent”… the same dumb argument wherein tubes and washers are somehow automagically a “suppressor in waiting” if they choose to prosecute it.

      1. No they would not arrest nor prosecute that in MD with a plastic blade! It’s clearly a toy! No constructive intent there and there is no way to replace the plastic blade with a metal blade!

        1. “an item that would commonly be described as a knife would be considered as such for the purposes of the legislation.”

          “Bladed articles

          These are any knife, knife blade, razor blade, axe, or other article with a blade or sharp point and which is made or adapted to use for causing injury to a person.”

          Doesn’t matter if it’s plastic. If it can be sharpened to the point of cutting, or it has a pointy end and looks like a knife, it is a knife. Ultimately it’s down to the judge, but you’ll be dragged into court nevertheless.

          1. You disregarded the part of the sentence that invalidated your argument: “and which is made or adapted to use for causing injury to a person”.

            This is not, so it doesn’t apply.

    2. Judging by the innocent items in the “seized weapons” posts, you could probably be arrested while having a cup of soup and see the plastic spoon seized as drug paraphernalia.

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