PET Bottle String Maker

I didn't invent this myself, but as it is a fun tool and I noticed there's no instructable of it yet, I made you one. All credits go to the person who came up with this idea for home recycling PET.

PET string or even making the tool can be great for DIY-projects with kids or even grown ups.

I made this instructable for the Industrial Design Center (IDC) in Kortrijk for Industrial Product Design (IPO) students.

Have fun with it!

Materials needed

• A disposable razor
• A piece of MDF (at least the size of two bottle bottoms). MDF is better than the multiplex used in this example because it has a better wear resistance (to prevent PET traces from being carved in the top).
• An even amount of flat washers of the same size. Make sure their radius (next to the hole) is wide enough to extend the width of the razor. This way you won’t have any unwanted razor parts sticking out.
• Two pan head screws
• A PET bottle

Tools needed

• An awl
• A screwdriver
• Pliers
• A cutter knife
• A pen
• One (or two) wood clamp(s)

*In the example pictures I used multiplex and washers of 2 different sizes as I made this out of leftovers. The only same sized washers I had, had holes too big for the pan head screws I found. So I put some smaller washers in between as a quick hack. Don’t do this if you can avoid it. :-)

Place a washer on top of the MDF just next to the middle. Align it with the front side of the wood and mark the furthest side of the hole with the awl. This is where you will insert the screw later.

Put a second washer about 1 mm from the first one and make a mark in the same way.

Tip: Putting it in the middle and not on the side of the wood ensures that you can use the tool with your left or your right hand as you wish.

Add an equal amount of washers on both the ones you used for the marking. Depending on the width of the PET string you want, add more or less washers.

Tip: Depending on the materials and screws you use it might be wise to drill a screw hole first to make sure the wood doesn’t split or doesn’t just get splintered.

Put the screws in the holes and start fastening them. Don’t tighten them completely. Leave enough space to easily add the razor blade.

Tip: Make sure the screws are long enough to get a very tight grip on the wood in the end. The strength of this fixation is a key element to the decent functioning of the tool you are making.

For the cutting element take apart a disposable razor blade with pliers.

Tip: Some people unscrew the blade of their pencil sharpener and use this instead. I tried this but the result wasn’t as satisfying as it didn’t seem to cut as well. (But that might have been because my sharpener is in fact already quite old.)

Insert the razor in between the washers on the height you want. The space between the wood and the razor defines the width of your PET string. Make sure no parts are visible except for the bit in between the washers. Try different heights on different bottles to see which suits your needs.

I had to cut off a bit of the side of the razor blade for safety reasons since it was just a bit too wide for the washes.

Fasten the screws very hard this time. If it’s too loose the blade won’t have the tension it needs to cut the PET and it will just bend or break.

To get started you need the bottle to have an even bottom surface and an upward side. As most PET bottles have a curvy bottom surface, you need to get rid of that first to get yourself a smooth start.

Fix a pen on a horizontal surface on the wanted height with one hand. With the other hand, turn the bottle around on the table so you end up with a straight line all around its surface.

Follow the line to cut off the bottom with a cutter knife. Try to get it quite straight so you have an even bit to start your string with.

Fixate the tool on a table with one or more wood clamps.

To start the string making, it’s important that you have a clean start. You can either just push the open side of the bottle gently onto the blade with an angle or you can make a small, angled cut with the cutter knife to have a smooth start. Gently push or pull it (with the pliers) through the washer towers until a sufficient piece is sticking out.

Now gently pull the string through the blades with the pliers with one hand, while you push down the bottle a bit with the other so it keeps it’s straight up position. This is important to ensure the string keeps its same width everywhere.

You can

• use it as a rope to keep things together
• just knot it around something (eg. Garden constructions, art works, prototypes,…)
• knot and heat shrink it to have a better fit
• weave it to create a canvas.

You can’t

• use it to keep together anything with a very tight grip as it isn’t elastic and quite slippery (even when you heat shrink it for a better fit).