tips on CNC cutting, Upcut vs. Downcut

We offer a wide variety of CNC router bits suited for cutting plastics. Some bits are general purpose, and some are more specialized. Often, router bit selection boils down to whether the plastic you are cutting is either soft or hard plastic. It can often be tough to know as most plastics seem pretty hard to the touch. It’s usually helpful to ask your plastics supplier which category your material falls under as the cutting properties of soft and hard plastics are quite different.

We had a customer ask what type of router bit we would recommend for cutting acrylic, PETG (polyethylene terephthalate), and styrene. Both PETG and styrene are considered soft plastics, and the recommendation was to use Onsrud 63-750 series router bits. These single-flute, solid carbide upcut spirals are more universal bits and are designed to provide a smooth finish in soft plastics with upward chip removal.

hard vs. soft acrylicThe trickier part of the recommendation is for the acrylic. Acylic can be classified as either soft or hard, depending on how it was manufactured. Extruded acrylic is soft, and cast acrylic is hard. If the acrylic you’re working with is cast, then you will need the Onsrud 63-700 series of bits which are better designed for the more rigid material. If the acrylic is extruded, then the 63-750 will work.


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