This YouTube video shows 10mm hex being machined in Nylon. Typical speeds, feeds and part preparation can be used. Rotary broaching is ideal for aluminum, brass and mild steel but can also be used for various plastic materials and nylon.

10mm Nylon hexagon made using Polygon Solution's GT Series Rotary Broach Tool Holder

10mm Nylon hexagon made using Polygon Solution’s GT Series Rotary Broach Tool Holder