Plastic Drilling Machining Guidelines

When drilling plastic components, pay attention to heat build-up or dimensional changes

Drilling Guidelines

Drilling is a common method for machining plastics. Below are general best practices as well as guidelines for drilling several performance plastics.

More heat is generated in drilling than in most other machining processes. Heat reduction is critical to minimize machined-in stress. A 90° to 118° drill point angle with a 9° to 15° lip angle is usually sufficient for most plastic materials. Acrylic drilling requires a 0° rake angle. The back side of plastic parts should be supported to prevent chipping during drilling. Drilling into unsupported areas should be avoided. The feed rate should be reduced when the drill gets close to exiting the material.

Deep hole drilling requires "peck drilling" for proper chip clearance and heat dissipation. The drilling depth should not be allowed to exceed 3-4 times the drill diameter before withdrawal. Drills must be sharp. Incorrectly sharpened or dull drills can induce high levels of stress into the workpiece. Proper chip ejection is critical. Poor chip ejection will cause frictional heat buildup.

Signs of improper drilling techniques include cracks, crazing, melted surfaces, poor finishes, and dimensional changes (typically undersize holes).

Special Measures: Preheat material to 250°F Caution when using coolants, susceptible to stress cracking Use carbide-tipped tools

The angle of the twist of the drill bit should be approximately 12° to 16°.

Heat before drilling: From 60mm diameter - PEEK, PPS | From 80mm diameter - PET, PBT | From 100mm diameter - Nylon 6

Material	α Clearance Angle (°)	ϒ Rake Angle (°)	φ Point Angle (°)	V Cutting Speed (ft/min)	S Feed (mils/rev)
ABS	8 - 12	10 - 30	90	165 - 650	0.008 - 0.012
Acetal (copolymer)	5 - 10	15 - 30	90	165 - 650	0.004 - 0.012
Acetal (homopolymer)	5 - 10	15 - 30	90	165 - 650	0.004 - 0.012
Noryl	8 - 10	10 - 20	90	165 - 320	0.008 - 0.012
Nylon 6	5 - 15	10 - 20	90	165 - 490	0.004 - 0.012
PAI	5 - 10	5 - 10	120	260 - 320	0.008 - 0.004
PBT	5 - 10	10 - 20	90	165 - 320	0.008 - 0.012
PEEK	5 - 10	10 - 30	90	160 - 650	0.004 - 0.012
PET	5 - 10	10 - 20	90	165 - 320	0.008 - 0.012
Polycarbonate	8 - 10	10 - 20	90	165 - 320	0.008 - 0.012
Polyethylene	5 - 15	10 - 20	90	165 - 490	0.004 - 0.012
Polyproylene (homopolymer)	5 - 15	10 - 20	90	165 - 490	0.004 - 0.012
Polysulfone	3 - 10	10 - 20	90	65 - 260	0.004 - 0.012
PPS	5 - 10	10 - 30	90	160 - 650	0.004 - 0.012
PTFE	10 - 16	5 - 20	130	790 - 650	0.004 - 0.012
PVDF	10 - 16	5 - 20	130	790 - 650	0.004 - 0.012
PPSU (Radel® R)	3 - 10	10 - 20	90	65 - 260	0.004 - 0.012
Ultem®	3 - 10	10 - 20	90	65 - 260	0.004 - 0.012
DuPont™ Vespel® Polyimide	0.50	5 - 10	90 -120	260 - 320	0.022 - 0.006