Experiment 32: A Little Robot Cart
270 Chapter 5
Cut with Care
You can saw ABS, but if you use a table saw, the plastic will tend to melt and stick to
the blade. These smears will get warm and sticky when you feed the next piece of
plastic into the saw, and the result will be extremely unpleasant. The whirling blade
will grab the plastic and hurl it at you powerfully enough to break bones. This is
known as “kickback” and is a very serious risk when sawing plastic.
If you have extensive experience using a table saw, you are actually more vulnerable,
because the reflexes and cautions you have developed while dealing with wood will
not be adequate for working with plastic. Please take this warning seriously!
Your first and most obvious precaution is to use a plastic-cutting blade, which has
a larger number of thicker teeth to absorb the heat. The blade I have used is a Freud
80T, but there are others. If you use a blade that is not suitable, you will see it starting
to accumulate sticky smears. This is the only warning you will get. Clean that blade
with a solvent such as acetone, and never use it for ABS again.
Regardless of other precautions, always wear gloves and eye protection when using
a table saw, and stand to one side when feeding materials into it. Personally, after
one episode of kickback that I thought had broken my arm, I prefer not to use a table
saw on plastic at all.
For long, straight cuts, the alternatives include:- Panel saw (big and expensive, but safe and accurate).
- Miniature handheld circular saw with a blade around 4 inches in diameter,
guided with a straight edge clamped to the sheet. - Hand saw. This is my old-school preference. My favorite is a Japanese pull-to-cut
saw, which makes very clean cuts: the Vaughan Extra-Fine Cross-Cut Bear Saw,
9-1/2 inches, 17 tpi (teeth per inch). If you use one of these, be careful to keep your
free hand out of the way, as the saw can easily jump out of the cut. Because it is
designed to cut hard materials such as wood, it has no difficulty cutting soft flesh.
Gloves are strongly recommended.
Figure 5-76. The perils of kickback. Plastic easily sticks to the blade of a table saw,
which will hurl it at you unexpectedly. Use other tools to cut plastic.