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How to smoothly cut plastic? Answered

I did a home automation project and I even fabricated PCB. I got a plastic box for encasing my PCB. The plastic box needs to be cut in two places to give the power chord and connection to the relays. I had soldering iron so I beat it up to a straight rod and tried to cut some plastic boxes that were lying around in my home. the heat was too much and even though the cut was somewhat accurate the heat caused the surrounding plastic to eventually melt and it became ugly.

Any idea how I can cut the plastic smoothly?

9 Replies

user
iceng (author)2016-08-23

Cut plastic with a saw blade running backwards.

That in not as complicated as you think, simply put the small tooth blade backwards on the saw motor shaft.

This will cut plastic without hazing or splitting, if you go slow.

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user
MisterHighway (author)iceng2017-11-14

Thanks for the tip, I'm going to try this tomorrow. I'd imagine this would work on a bandsaw as well.

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user
rickharris (author)2016-08-24

Cut a rough hole and push a grommet into it to finish off the edges.

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user
seandogue (author)2016-08-24

I use an exacto to cut into the plastic to trace the outline of an area that will be removed, even if I'll be using something else (coping saw, dremel with cutting disk, etc.) for cutting the full depth. This avoids or at least minimizes cosmetic damage at the surface. It also gives you a guide line to work from.

Afterwards, I use jewlers files or simialr to clean things up.

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user
Yonatan24 (author)2016-08-24

What type of plastic?

Try using a really fine toothed blade in a circular/table saw, or make a hot wire cutter (Google it)

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user
Josehf Murchison (author)2016-08-23

As long as you are cutting the plastic the edges will be rough.

Cut rough holes you can use a dremel, a keyhole saw, a drill, and yes a soldering iron, then dress the edges with a fine file and work your way to sandpaper.

The most important thing, TAKE YOUR TIME, if you hurry you will mess it up.

Plastics with perfectly smooth edges are usually molded that way, but some are polished to a smooth edge by using progressively finer grit sandpaper up to 600 grit and finishing with compounder.

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Kiteman (author)2016-08-23

Use a "step drill bit" to cut holes in thin sheet materials.

Eg http://www.harborfreight.com/3-piece-titanium-nit...

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verence (author)2016-08-23

Use a drill for small round holes, a jigsaw for bigger or square holes and some needle files to clean up. Go slow, you want to cut, not melt.

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Vyger (author)2016-08-23