My chopper I and chopper II ar both e a POS they both cut at an angle anyone know of a better unit for cutting plastic stock ?

Paper guillotine’s work well depending on the thickness of the plastic.

The problem is not your Chopper - it's how you have it set up. Those razor blades have a thick edge at the top. When you screw them into the cuttng arm, the blades cants in at an angle. You can easily alleviate that by using very small washers or pieces of shim stock. Once your blade is perfectly vertical your cuts will be too.

The blade can sometimes track at an angle. The easy solution if you are making straight cuts is the cut partway through, then flip the part and cut form the other side. If you have it set up for angled cuts try making the cut in multiple "passes". Cut partway, lift the blade and let it spring, cut again, etc.

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