Monday, April 23, 2018

How Do OTF Knives Switchblades Work?

Sup guys, Atech here and welcome into another post in which I will show you how do OTF automatic knives or switchblades function.

I decided to make this post because many people, especially non knife folks are really surprised by the action of the otf knives when I showed it to them, so they are like – “oh man, that’s so cool, how does it work, what is this magic” and so on.
There are videos online that show these knives in the disassembled state but when disassembled it is really hard to grasp how they actually work.

So for this purpose I got this clear top OTF knife that allows me to show you the action without taking it apart.

There are few types of these mechanisms but most work by the same principle and today I will show you the most common one that is also used in the Microtech Ultratech knives.

Let’s start:
OTF knives are usually built from a few components:
1. The bottom scale – that holds the mechanics - and is generally built out of a light metal, such as aluminum, like in this case.
2. The top scale – which is flat and just presses the mechanics from the top, so could be produced from different materials, such as aluminum, carbon fiber or even clear plastic like in this case.
3. The actuation switch, which rides along the side.
4. The main plate that is moved by the actuation switch and coordinates the function.
5. The spring with hooks that is used for the tension.
6. The latches with springs that hold the blade in the open and closed position
7. And of course the main blade that is fired out of the front of the knife.

So how does it all work:
In the closed position, when we move the switch it in its turn moves the main plate and loads the spring that is connected to the blade by a hook. The blade at this point is held by the bottom latch, so it doesn’t move and tension becomes higher.
The main plate has this curve that moves the bottom latch and just as we get near the end of the path of the switch, it moves the latch all the way to the side, which releases the blade that flies out by inertial force and is locked by the upper latch.

When we close the knife it works just the same but another way around – we pull the switch, it slides the plate down and builds up tension on the spring, the curve in the plate moves the top latch and opens it, and the hook that is connected to the spring pushes the blade down by this nob and is secured down by the bottom latch.

As you can see it is pretty complicated mechanically and all the components have to work in cooperation in order for it to work properly and reliably.
BTW – I really like this cleartop version because I can see if there is any dirt inside and clean it out before it does damage to other components.

Now I would like to show you what happens if we fire a double action automatic knife into a hard object. I will use this pad.

As you can see – because the blade didn’t reach the latch it stopped and now moves freely in the handle, the plate as well.
But it isn’t broken, all you need to do to make it work again – just pull the blade all the way out, it catches the latch and fires just as it should once again.

I hope you enjoyed this post and found it interesting – if you did please give it a thumbs up and subscribe if you haven’t already.

Link to the ClearTop OTF: The Mini Version: Original Microtech Ultratech:

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