DIY hot knife

I bought some plastic boards from New market last weekend. I say plastic board cause thats the only name the shop keeper could tell me. I think its a closed cell polyethylene board. I am probably wrong. but the properties are similar. Its hard, its relatively light but approximately 10 times heavier than Styrofoam and does not bend. It breaks before deforming.

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Plastic Board. Source: ABC Stationary New Market, Dhaka

 

They are pretty strong but i was able to make a clean cut with a Utility knife just as the shop keeper told me. But it takes a lot of patience and skill to make a clean cut and large shapes are just that difficult to pull off.

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Recommended cutting tools by shop keeper

 

As always the lazy mind has a tendency to look for easier ways. And I came across “heated knife” the tool used to cut this type of materials with ease. I tested the concept by heating some Utility Knife blades using fire and it worked.

Unfortunately i dont have a heated knife lying around. Googling around looking at how it works I thought it would be relatively easy to make one using a soldering iron.

I have this pretty “old” soldering iron with wooden handle and large tip. Since I have a spare i decided to make a knife out of it.

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Flattened Soldering Tip with some sanding to sharpen the edges.
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How thin it is from the side

 

 

 

 

 

 

 

 

 

 

The method I used is simple. I heated the soldering iron tip high and then hammered it to make a flat shaped head.

Once I was satisfied with the hammering a little sanding gave the edges some sharpness.

CAUTION: Using hot knife to cut plastic will release hazardous fumes. Try not to breath on them.

I tested the knife on a piece of board.

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Hand cut plastic board using home made hot knife

 

Although it wasnt like cutting butter. But it was definitely close to cutting vegetables 🙂 . I managed to cut a square board with smooth edges in less than a minute. It takes a while to get the tip heated. And perhaps due to its extended surface it looses heat faster and needs a break after cutting a while.

The edges are relatively smooth as well. You can make the edges better by slicing off the extra melted drops of plastic with a knife.

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Rough margins but smooth ends.

I am pretty impressed by the results, I will surely use this new plastic board for my future prototypes. I cant wait for the weekend to get around. 😉 .

 

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