The 118° included point angle is the factory default for a reason. It's a compromise that performs well across a wide band of common materials: low-carbon steel, cast iron, many alloy steels in the annealed condition, and medium-hardness plastics.
At 118°, the cutting lips have enough wedge angle to shear steel efficiently without generating excessive heat or requiring extreme feed pressure. The chisel edge is moderate in length — not so stubby that it requires extreme thrust, not so long that it wanders badly before engaging.
When to use it:
One caveat: 118° is not great at self-centering. On flat or lightly pre-spotted surfaces, the broad chisel edge will skate. Use a center punch or a spot drill.
Step up to 135° when the material fights back. The flatter geometry distributes cutting force over a wider area, which matters enormously in hard materials and alloys that work-harden under the chisel edge.
304 and 316 stainless steel are the canonical case. These alloys work-harden rapidly under sustained pressure — the kind of pressure an undersized or poorly angled chisel edge generates as it scrubs rather than cuts. A 135° split-point (with web thinning) gets into the cut fast and keeps moving before the material can harden ahead of the tip.
Other applications:
The 135° geometry also dramatically improves self-centering. The flatter angle brings the cutting lips to engagement sooner, which means less wandering before the drill stabilizes. On CNC work where you're eliminating the spot drill operation, 135° split-point is almost always the right call.
A practical note: resharpening to 135° requires either a drill grinder with the right fixture setting or a skilled hand-grind. The geometry is less forgiving than 118° — if the half-angles aren't symmetric, runout and wandering get worse, not better. This is one reason professional resharpening pays off on the harder angles.
When you drill into dead-soft copper or fully annealed aluminum, the problem isn't hardness — it's the opposite. The material is so compliant that a standard 118° drill will grab, chatter, and pull itself through in an uncontrolled lunge that tears the hole rather than cutting it cleanly.
Flattening the point to 90°–100° reduces the rake angle at the cutting lip. This gives the lip a more scraping, controlled action rather than an aggressive dig. The drill still cuts efficiently but doesn't self-feed so aggressively that it yanks the part off the table.
This range covers:
Sixty degrees is aggressive and flat — it looks wrong if you're used to steel drills. But for thermoplastics, particularly acrylic (PMMA), polycarbonate, and nylon sheet, it's the right answer.
The problem with drilling plastics using standard geometry is heat and grab. A 118° drill in acrylic generates enough friction heat to melt and re-fuse the hole wall, leaving a cloudy, undersized bore. The steep cutting angle also grabs on breakthrough, cracking the back face of the sheet.
A 60° point does several things simultaneously:
Pair 60° geometry with slow spindle speed, high feed (don't dwell), and back the workpiece with a sacrificial board. For acrylic especially, letting the drill dwell — even for a fraction of a second — melts the cut surface.
Point angle is not a fine-tuning variable. It's a primary geometry parameter that determines how force is distributed, how heat builds, how aggressively the chisel edge presses, and how well the drill centers itself.
Using 118° in stainless causes work hardening, burned lips, and broken drills. Using 135° in soft aluminum causes chatter and grabbing. Using a standard steel drill in acrylic leaves a melted, cracked hole. None of these outcomes are mysterious — they follow directly from geometry mismatch.
The good news is that resharpening lets you dial this in. A worn drill going out for reconditioning can come back with a different point angle if your material mix has changed. That's not possible with disposable drills — you'd need separate bins for every material. With resharpenable HSS, you have control over the geometry every cycle.
If your shop runs a consistent material mix, standardize your angles and label the bins. If you run mixed work, keep a reference card — like this one — so the person loading the spindle makes the right call before the program starts.
Mail in your dull HSS drills. We'll sharpen them on our WinsloMatic — back to spec, ready to cut.
Get a Quote →