Geometry & Mechanics
Drill Point Angle Chart by Material
Selecting the proper point angle prevents drill wandering, reduces breakthrough burrs, lowers machine thrust force, and maximizes edge life.
| Point Angle | Tip Length Multiplier | Trigonometric Formula | Recommended Materials | Machining Characteristics |
|---|---|---|---|---|
| 118° Standard | 0.300 × D | (D / 2) / tan(59°) | Mild Steel (1018, 1045), Aluminum 6061, Brass, Cast Iron, General Purpose Wood/Plastic | Universal point angle. Has a broad chisel edge requiring higher thrust force to penetrate. Can walk on curved surfaces without a spot drill. |
| 135° Split Point | 0.207 × D | (D / 2) / tan(67.5°) | Stainless Steel (304/316), Alloy Steels (4140/4340), Titanium, Inconel, Hard Structural Steel | Four-facet self-centering point. Eliminates center walk, reduces thrust force by 45%, and breaks chips faster in tough work-hardening alloys. |
| 140° High-Performance | 0.182 × D | (D / 2) / tan(70°) | Solid Micro-Grain Carbide, High-Speed CNC Machining Centers, Deep Hole Drills | Optimized corner strength for brittle carbide substrates. Flatter point distributes cutting loads evenly, resisting chipping at high SFM. |
| 90° Spot / Point | 0.500 × D | (D / 2) / tan(45°) | Acrylic / Plexiglass, Thin Sheet Metal, 90° Spotting & Hole Chamfering | Sharp point slices through thin polymers and acrylic without grabbing or shattering the exit face. Creates a ready 45° lead-in chamfer. |
| 60° Center Drill | 0.866 × D | (D / 2) / tan(30°) | ANSI / ISO Combined Drill & Countersinks for Lathe Workpiece Centering | Matches standard 60° lathe dead/live centers. Not intended for CNC spotting because twist drill corners will contact the steep 60° wall first. |
Need to calculate exact depth for blind or through holes?
Compute conical tip offsets, cylindrical depth, and total travel with live SVG cross-sections.