Glass-fibre-reinforced polyamide 12 (G/PA12) composite, a material with considerable potential in the automotive industry, poses notable machining challenges owing to its low glass transition temperature, low matrix stiffness, and the abrasive nature of the glass fibres. Although near-net-shape manufacturing processes minimize excess material, the free edges often require precise trimming to achieve the specified product accuracy and quality. In this study, optimal cutting conditions and tool geometries for edge trimming of G/PA12 composite plates were investigated. A two-stage experimental design was adopted, beginning with the identification of principal control factors using a standard polycrystalline diamond (PCD) cutter. These findings were subsequently compared with results obtained using various double-helix cutter geometries. Double helix cutters have demonstrated significant improvements in surface quality, achieving up to 100 times improvement with a 20% reduction in temperature and only a slight increase in resultant force. An elevated feed per tooth rate was shown to further enhance surface quality, although at the cost of higher cutting forces. A highly accurate cutting force model was formulated, explicitly accounting for both rake angle and helix effects. Temperature measurements obtained with an infrared camera and based on experimentally determined emissivity values revealed that the glass transition temperature was consistently exceeded; however, the melting point was not exceeded.