This tutorial shows a very simple way to make a gravity
engaged hidden blade.
What you’ll need:
- Dresser drawer slide (grabbed one from Home Depot)
- Some sort of electrical saw (I used a circular saw)
- Plastic or wood (whatever you want to make the actual blade
part out of)
- Dremel or sander
Grab your slide and dismantle it. There should be a black
piece near the end that you can remove.
Take the inside slide out and be
careful to collect all of the small metal balls that help it slide.
outside part of the slide and hold it up to your arm. You’ll want to cut it to
about the same length as your forearm.
Be sure not to cut the side where you removed the piece of
From here on out, any of the pieces that you cut will be
pretty sharp afterwards so be careful! It’s best to use a dremel or a sander to
smooth out those sharp edges.
Now, you’ll have to make two small cuts on the end you just
cut. Take a pair of pliers and bend the ends inward. This will stop the inner
part of the slide from completely sliding out of the outer part.
Take the inner part of the slide and cut it as well. You’ll
want to cut it to less than half the length of your forearm. It really depends
on how long you want your blade. If the inner part of the slide is longer, your
blade won’t extend very far when the mechanism is ‘engaged’. If you make is
shorter, the blade will extend more. It really just depends on how you want it
Place the the balls (only as many as you need) and the inner
part back into the outer part of the slide. Replace the plastic piece. Make your
blade. It has to fit onto the inner slide without overlap so that the inner
part can move and so that the mechanism looks less bulky.
I used an old ruler that I painted gray. It isn’t very
convincing but it’s acting as an example for now.
The last step which isn’t shown is to place a piece of felt
between the inner and outer part of the slider. The idea is that you want the
blade to stand up against gravity but, with a shake of the forearm, to slide
out. Therefore, a little bit of friction is required. A small piece of felt can
be pasted on the outer part so that the inner part catches on it.