How do you guys cut your sheet styreen and get those perfect angles?

jake88

Sr Member
If the plastic is .020 or thicker I use scissors and this leads to bowing and bad lines. How do you master scratch builders do it?:unsure
 
Scribe with a knife (exacto or box) using a metal straight edge as a guide, then flex on the scribe line and it will snap a straight line.
I've done it on up to 1/8" styrene and ABS.
 
tools like this are useful:
82439.jpg
I use an OLFA 300 knife like this one:
images.jpg
And like mentioned above, cut a few times then snap it over to separate. Thin styrene like .5mm can be cut right through on one pass and I use a self healing cutting matt. Sometimes the thicker styrene can leave a bit of a bur or a raised edge, I just drag my knife blade across or use a file to remove it.
This is useful too, make sure you get the thin beam square, not the traditional square.
83261_R.jpg
 
As has already been said, a sharp scalpel or Xacto will do the trick. I don't have an engineer's square, I use an aluminium ruler with a rubbery underside so that it doesn't slip. Seems to work for me; curves are more the tricky part, but apply the same scribe, cut, snap technique and it should work out fine
 
the machinist squares are small, only 4 inches long, and have a low profile so they lay flat on thin sheet material like styrene. If you notice in the two lower pictures the traditional square sits high, where as the thin-beam sits low and the cutting edge is close to the material you're cutting.
Make sense?
 
Ah yes, it does, although I was looking around for squares and carpenter squares seem to not have a raised edge like the ones above, instead shaped completely flat on both sides of the right angle. I was wondering if those would work for thin styrene too, though perhaps a little less accurate?... huh.
 
Ah yes, it does, although I was looking around for squares and carpenter squares seem to not have a raised edge like the ones above, instead shaped completely flat on both sides of the right angle. I was wondering if those would work for thin styrene too, though perhaps a little less accurate?... huh.

I'm quite sure those would work just as well, if you can find small ones. Most of the stuff I cut is not very big, so that's why I use the machinist square.
 
Stores like TAP Plastics sell knifes specifically for cutting plastic. They have a very even V profile.
 
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I never get the length of the cut perfect or at a perfect 90 degree angle, so after the "scribe and snap" technique described above I use sandpaper to sand the side I just cut and use a square to make sure the angle is 90 degrees. If I ever have to have a different angle I'll get one of those protractors for cutting angles from the hardware store.
 
I think the problem some guys have with the scribe and snap method is that they just bend it in one direction until it snaps. for a cleaner cut bend it half way in the outer direction, then snap it off back in the other direction. if that makes sense.
 
Also a variety of straight edges is useful. Thin metal for example can be useful for cutting something that isn't flat... Also follow the measure twice cut once methodology... line it up - take a good look at it, measure if applicalble and then holding the straightedge firmly (sometimes I'll tape it or clamp it for a long cut) ... Then cut.

And when using the exacto knife scribe and snap method, I use a new(ish) blade and make several light passes each one getting a little deeper until its almost cut through then snap. If the styrene is thin the snap step is usually not needed ;)

Jedi Dade
 
I go between a scalpel with a steel ruler and engineers square and a laser cutter if I'm feeling lazy or cutting complex shapes that I can't do by hand or need tight tolerances. As for circles I prefer a set of dividers over a circle cutter I find the circle cutter flexes to much and I end up with the cut spiralling out or in.

If you get a set of these and grind the tips to a sharp point they will work a lot better than a circle cutter on styrene. Just search dividers on Amazon and you can pick them up fairly cheaply.
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