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I like knives, and Airsoft, and making things, so i put that all together and made some practice knives out of PVC. They can be used for Airsoft or other Milsim sports, messing around, or training. They are cheap, durable, light, and pretty safe.

These have no sharp edges, but do be warned, they are still not really toys, they can bruise or break bones if swung with enough force, or put out an eye if you get poked.  These might also be illegal in your area, so if you really care about laws pertaining to your possession of a dull plastic knife, then follow  them.

Step 1: Tools and Materials

As far as tools, surprisingly, not much, It all depends on the level of detail you want. Items with an asterisk* are not optional.
  • *vise, bench clamp, or other clamp with a large clamping area and a really strong grip.
  • *Heat gun. I use a Wagner Power Stripper. They aren't too hard to get or too expensive. Look at your local hardware store, it shouldn't be more than $30 (US). Make sure you keep the receipt, if it doesn't get hot enough to melt the PVC, then you will need to trade it in for another one. In theory, you could use a flame or a torch, but they are way hotter than you need and much more dangerous.
  • Rivet gun or some other fastening tool to secure the grips.
  • Sand paper
  • *File, to shape the tip.
  • *saw to cut the pipe
  • Rotary Tool
Materials- again, items with a * are required
  • *PVC pipe. I use grey 1/2 inch PVC for this blade, but all kinds work. Try different colors, and different diameters. You can use one size of pipe for the handle and another for the blade. Oh, and by the way, this is all you really need to make a really basic knife.
  • PVC reducer sleeve
  • Bicycle grip- I found mine on the side of the road. If you find an old crappy bike, take off the grips and use them, or go buy them. They only usually fit 1/2 inch pipe though.

Step 2: Cut Pipe to Length

Cut your pipe to length. It really depends on what size of knife you want. Decide on a blade length, and a grip length. If you want to add a hand guard or a fitting in between the grip and the blade, don't forget to compensate for the length.

Anyway, I decided on a 9 inch blade, a fitting in the middle, and the grip was the length of the bike handle I had.

Mark where you want your grip to start on the pipe, this is important.

Step 3: A Safety Note

The whole process of this build revolves around heating PVC pipe until it is pliable and then squishing it. PCV (That's Poly-Vinyl Chloride, for those impressed by big words), is pretty toxic stuff when you heat it. I don't actually know what is produced with it is heated, but it smells horrible and gives me a terrible headache. I don't know if there are any long-term effects, but i would be willing to bet that breathing the fumes for any length of time will definitely make you more stupid.

So, DO THIS IN AN EXTREMELY WELL VENTILATED AREA!!! Preferably outside in a windy area, and wearing a respirator for extra safety. Basically, if you smell the odor of heated PVC, go some where more ventilated.

Step 4: Shape Any Handle Fittings

If you chose to put fittings on your handle, and they need to be shaped to make them fit, do this now.

I chose to use a 1 to 1/2 inch reducer fitting. This will not slide freely on the 1/2 inch pipe, because there is a stop ring on the inside.
I used a sanding bit on a rotary tool to remove this ring so the fitting will slide smoothly onto the 1/2 inch pipe.

Step 5: Heating and Shaping the Pipe

Ok, get your heat gun and put it on high. Get your pipe and start heating the end that will be the tip of the blade. Only heat in about 1.5 inch sections. Hold the tip of the heat gun about half an inch away fro the surface of the pipe and rotate the pipe so it is evenly heated.
your pipe is heated and pliable when the surface begins to discolor and char. You have a bit of leeway here with the heat, but generally, your pipe is pliable after it discolors. Make sure your pipe is discolored all the way around it, so it will all be pliable.

Next, quickly turn off your gun and set it somewhere safe where the hot nozzle won't melt anything. take the hot end of the pipe and clamp it in the vise. Just keep clamping until it is totally flat. Clamp it really tight. Wait about a minute, while holding the pipe steady, then take it out of the vise and continue the process along the whole length of the blade.

As you continue down the length of the pipe, be sure to overlap your heating sections slightly, and always heat a little extra space around the edges of the place that will be clamped. This makes a smoother blade. Always clamp the blade to the same thickness each time you clamp.

If your blade bends or gets zig-zagged in the process of heating, don't worry. We will straighten it later.

Follow the pictures for direction. This process seems really difficult, but it is really simple and you will learn it in about ten minutes. If it seems really hard, practice on a piece of junk pipe before you work on your actual blade.

Step 6: When to Stop Heat Forming

When you get near the grip part of your blade, start test fitting your handle pieces in between each clamping. You will end up with about a 1/2 inch section between the base of the blade and the start of the handle. Once it looks good to you, or the fittings start getting hard to put on, stop clamping.

Step 7: Straightening the Blade

Chances are your blade came out kind of bent or zig-zagged. This is an easy fix. Earlier, we were clamping the blade vertically in the vise. Now, we will be clamping the blade horizontally.  Start at the tip again, and heat a section the length of the vise jaws on one edge of the blade. Clamp this edge tight, let cool, and repeat. Like the first clamping, overlap the clamped parts, but do it a lot more here. Continue along the same edge of the knife until you reach the grip, then flip the knife over and do the other edge.

Any more adjustments in the blade can be done by applying heat and bending at your discretion. I warn you though, it is easy to get carried away. Keep in mind that these blades will never be totally straight or smooth. I discovered that slight bends can be smoothed out later, when you shape the blade.

Step 8: Shaping the Blade

Take your blade and mark out where you want the tip to be, and how you want it to look.

Rough cut it with the saw, then take the file and smooth it out.

Bevel the edges, blunt the tip, file down any stubborn bumps.

Once the file work is done to your liking, now take the sandpaper and smooth out any finer impurities like burn marks or lines from clamping. You probably won't manage to sand down the clamp lines, so don't worry about it too much. It looks ok with them there.

At this point, you could take your knife and call it done. The simple shaped blade works fine with no grip. However, I wanted a grip, and I assume most people will.

Step 9: Get a Grip

Put all your grip pieces on and attach them how you see fit. I used way too many rivets to attach my fitting and bike grip. I did a little bit of light sanding on the fitting with the sand paper to remove any letters and smooth the edges a bit.

There you go, Done!

Step 10: Finished Product, Future Plans, What Have You.

After the first knife, I made another. This one was all from white PVC, with a 1 inch handle, a 1/2 inch blade, and a reducer between the two. This one is a bit smaller than the last. The handle was a to see how far I could take the heat-forming process. It worked like a charm, and I almost like this knife better than the other.

I have yet to make a blade with a thicker diameter of pipe,  but I am sure it works the same way. I don't know if you could make a full-sized sword, but I will probably try at some point.

If you make a knife, post pictures and I will add them here!
Stupid question, but is it possible to use this as a throwing knife? I wanted to know before I attempted.
<p>If you threw it at cardboard, maybe. If at wood then no.</p>
I suppose you could, but it's not super durable, so don't be surprised if it breaks. <br> <br>Try it though, post pictures!
I'm glad you added that warning about heating PVC outside. Had to do that with my PVC didgeridoo this week. PS I llike the knife!
I like the didgeridoo!
Yeah, good ventilation is mandatory. Thanks! If you like this project, check out my Airsoft carbine conversion for more PVC forming.
I love the second one! Nice job! <br>Sunshiine
Thanks! <br>
First! and by the way these knives are great, 10
Thanks!

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Bio: I am a recent graduate of the Sustainable Manufacturing program at California State University Chico. I currently consult with local businesses and provide freelance design ... More »
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