Cutting Plastics ~ Luthiery Laboratories

Cutting Plastics

Cutting plastics presents a special problem in that many plastics generate significant heat and can melt. This is especially a problem with clear plastics and thicker materials.

Often you'll find that the material simply melted in front of the blade and re-solidified behind it, so you haven't actually made a cut, more like a weld. In this situation, if you pause cutting, the blade will become trapped in the material. Then you have a real problem.

Jigsaws blades heat up very fast in almost any material and are especially a problem in plastics.

The long blade on a band saw makes a good heat sink and is fairly resistant to heating, but thicker materials are still a problem. Even if the blade stays cool, the material can still melt around it.

Most scroll saw blades heat up pretty quickly and give the welding effect I described. For cutting plastics with a scroll saw, use a "skip-tooth" blade. This is a blade that looks like every other tooth is missing, and is much more resistant to heating. They are seldom labeled as such, just look in the package for what I described.

Cutting

You could conceivably build a guitar with just a coping saw, pictured above. I would hate to try. I have listed here an assortment of hand and power saws that would work much better.

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Pickguards

The easiest way to make a pickguard is to go to eBay and buy one, ready-made. However, if that doesn't suit your project, you can also find a wide assortment of blank materials to make your own design from. Work out your design full-sized on paper first.

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July 17, 2020

A Decent Scroll Saw

July 17, 2020

General International 1.2 Amp 16 in. Variable Speed Scroll Saw with Flex Shaft LED Work Light

This is another piece that I got for free for review. Normally it is about $90. I would have soldiered on forever with my ancient Craftsman saw because I am cheap, but free is free and even better than cheap, and this is a nice upgrade. Compared to my antique model, this saw is variable speed, easier to change blades and takes both kinds, adds a work light, dust blower and dust port, and is lighter with a bigger table.

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RetroBrite

"RetroBrite" is a name for a process that restores old yellowed plastics to new. Many plastics yellow or darken over time. RetroBriting can reverse this aging, but with a number of caveats that, in my opinion, make it pretty useless. While the process actually does work - it reverses the discoloration - the effect is temporary. After a few months, the plastic will return to its yellowed state. When this happens, you can repeat the treatment, but at some point the chemicals involved are going to start to degrade the plastic.

My first experiment was whitening some yellowed tuner knobs, and it did work. With nothing more than sunshine and hydrogen peroxide, the knobs lightened considerably. That was several years ago, and today the knobs are as yellow as ever.

What causes this yellowing? It is variously attributed to sunlight, oxygen, bromine content, and other causes. While all of these things can contribute to it, none of them are necessary. Some plastics simply turn yellow with age, and nothing will stop it. In my experience, the real culprit is simply bad plastic, and the only real solution is replacement.

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