Functional Retractable Assassin's Creed Hidden Blade (Xiphoid)

About a year ago I was inspired by a friend to make a xiphoid, commonly known as the Assassin Creed hidden blade. After making a video on YouTube that showcased my first design I received endless requests to make tutorials or sell my model. However, I wasn't satisfied with my first design and I came up with a second one that is sleeker, easier to use, and just plain cooler :D Since I'm a visual and hands-on learner, I've also created a a two part tutorial on YouTube that goes through all the steps and shows you the entire process. However, before you watch the video or go through the steps below I just want to let everyone know that while you can follow this tutorial and copy my design, I think it would be more beneficial if you tried to understand how everything works so that you can make your own changes to improve my design. Enjoy! I'll post the links to the videos when they're uploaded.

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Youtube Video Part 1:

Youtube Video Part 2:

Step 1: Materials

Richelieu 16" 400mm Center Mount Slide (Lowe's $5)
9" or 22.8 cm Letter Opener (Staples $3)
Hillman Extension Spring 1/4" x 3" x .025" OR use a spring with a longer length only that can be cut down to size (Lowe's $4)
14-Count #6-32 x 3/8-in Round-Head Standard (SAE) Machine Screws with Nuts (Lowe's $1.50) AND some panhead screws of the same size
IRWIN Tap and Die Set 6-32NC (Lowe's $5)
6" 150mm General Steel Rule (Ace $4)

Step 2: Modifying the Drawer Slide: Dismantling & Large Slide

The first thing you need to do is take apart the draw slide. On the back there should be some tape that you need to pull off. Where the tape was is a part that you can slide off, remove it. You won't be needing these pieces so you can toss them away.

Now you need to separate the slide into its three parts which I call the Large Slide, the Slider, and the Small Slide. To do this you need to fully extend the slide. Once you have done this you'll notice a notch in the Large Slide that prevents the other pieces from falling out. You need to remove this piece in order to modify each piece. In the photo above you can see where I cut Large Slide, the angled cuts are purely for aesthetics so it doesn't matter if you prefer to cut straight down. Just make sure to keep the hole within where you cut so that you won't have to drill another one.

Once you have removed this notch you should be able to slide each part out. MAKE SURE THAT YOU HAVE A CONTAINER OR MAGNET TO CATCH ALL THE BALLS WHEN YOU SLIDE OUT THE SLIDER.

Take the Large Slide and measure out 9 7/8" (if you go with 10" it's not a big deal, I'm just going with what worked for me the first time). Once you have marked it go ahead and cut it. Make sure after all your cuts you grind down the edges to make it smooth.

Step 3: Modifying the Draw Slide: Small Slide

This part is straight forward, you need 3" of the small slide. Make sure that the 3" that you use do not have pre-drilled holes in them. We are going to make and tap our own holes. Once you have cut your small slide place it in a vice, with just the bottom edges in the grip, and compress it gently. The purpose of this is to allow the small slide to slide back and forth smoothly and easily once placed back on top of the slider and large slide. If this is confusing refer to my YouTube video, it's a lot easier to see what I'm trying to explain.

Step 4: Modifying the Draw Slide: the Slider

The next thing to do is cut a slit in the Slider to hide the spring in. In my previous model I had the spring on top but I decided I didn't like how it looked on top and so I have hidden it in this model. When cutting this slit make sure that it's 2.5" long and just a hair wider than the spring so that it doesn't scratch on the sides when extended. When cutting try not to bend the metal. Remember patience is key, so cut this gently and slowly!

Step 5: The Blade/Letter Opener & Small Slide

For my Xiphoid I decided to use a letter opener as the blade. However, if you want something that looks a little more lethal and want to make your own blade just understand that where we drill our holes may be a little different. If you use the letter opener I used you will already have a hole drilled into it and will only have to drill three more holes. Using the photo above line up the letter opener on the small slide and make sure that the blade curves down (this only applies if you are using the same letter opener as me). Once you have marked everything go ahead and drill your holes and then tap and counter sink the appropriate holes (refer to photos). Now you need to take three of your flat screws and screw them all the way into a nut. Once each screw is in a nut place it in a vice and cut the portion of the screw that is not in the nut. Once you are down unscrew the nut (the purpose of the nut is to reform the damaged threads of the screw once you cut it) and use these where you tapped your holes.

Step 6: Large Slide Drilling: Blockers

So now that we have cut our large slide we need a way to prevent the slider and small slide from coming out. If you have been following me exactly you will already have one hole at the end of the large slide. All you need to do for this is place a screw and three nuts in this to block anything from going out the back. For the front we will need to make our own hole. Because the blade is in the center of the design the block at the front will need to be off set. In the photo above you can see that I drilled my hole on the right. Once you have drilled this hole counter sink the bottom side of the large slide and use two nuts on top.

Step 7: Assemble

Now that you have the large slide, slider, small slide, and letter nearly finished you need to put them together. Slide the slider on and use one ball for each segment (the slider has segments that have three holes for balls, I only use the center hole of each segment to cut down on friction) and them force the small slide on with the letter opener on. It should start to look like the finished product. When you put the small slide on push it all the way forward and then force the slider all the way forward as well so that they both hit the front block together. This is key otherwise the design won't completely work.

Step 8: Ruler

Take out the ruler or piece of metal that you are using for the locking mechanism (any spring metal will do) and place it on the back of the large slide with enough protruded from the front so that when bent the metal will touch the letter opener at an angle. I highly recommend you watch the video for this part since I can't explain it very well. You can also use the photo above and just copy the dimensions. Once you have cut the ruler to size you will have to drill three holes into it. Two holes will be used to mount it to the large slide and one hole will be used for the string, which I will explain later on. Tap the holes on the large slide and use panhead screws to attach the ruler.

Step 9: Spring

Take your spring and make it 3" long. 3" is from the outer loop to the outer loop NOT the compressed portion of the spring. Once you have cut it and bent a new loop at the end take this spring and put one loop underneath the nuts of the back block on the large slide.

Step 10: String

If you have been following me exactly, the back of the large slide should have a hole that was already drilled. Take your string and knot it up and then pass it through this hole. Then thread the string underneath the slider towards the spring. Loop it around the spring and then thread it over the slider but underneath the small slide. Then pass it through the hole on the letter opener. Next, move the letter opener and small slide all the way back until the small slide hits the back block. Pull the string taunt and then knot it as close to the letter opener as possible. Now take a new piece of string and tie it on the ruler/locking mechanism. Next create a loop or tie the string to a key chain ring.

Step 11: Finished

If you assemble everything together now you should be finished. When swung the blade should be locked by the ruler and then release when the string is tugged. If the blade doesn't contract all the way you could 1.) compress the small slide even more 2.) Use less balls so there's less friction 3.) Use a different spring