Types of Drill Bit Tips | 118° vs 135° And Material Selection

Nothing kills a drilling job faster than the wrong tip. A bit that chews through mild steel will skate across stainless steel, and one that bores into concrete will shatter on a hardwood plank. The difference comes down a few millimeters of geometry and the metal alloy the tip is made from — factors that are easy to learn and impossible to fake on the shop floor.

What Do The Two Standard Point Angles Actually Do?

Every twist drill bit has a point where the cutting lips meet at the center. That meeting angle determines how the bit enters the material and how it handles heat and pressure.

118° (standard twist drill): This is the sharper, more aggressive angle. It bites into material fast and cuts cleanly, making it the right pick for mild steel, aluminum, wood, brass, PVC, and most plastics. The trade-off: the sharp tip wears faster under heat and chatter, so it’s not ideal for hard alloys.

135° (split-point drill): The flatter angle spreads the cutting load across a wider area, reducing the pressure at the very center. This prevents “walking” — that frustrating skid across the surface before the bit catches. It’s the standard for stainless steel, carbon steel, cast iron, and hardened tool steel. The split-point tip also eliminates the need for a center punch in many cases, because the bit stays on center by itself.

Specialized angles: A 90° point works best for soft plastics and thin aluminum where a standard 118° would crack the material. A 140° point is used in extreme hardened steels where maximum heat resistance is needed. The chisel point — the center web of a standard twist drill — sits around 60° and is the part that tends to push and wander without a centering aid.

Which Bit Materials Match The Job?

The tip’s material determines how long it stays sharp and what it can survive hitting. Here is how the major grades break down in practice:

High-Speed Steel (HSS) is the workhorse. It withstands temperatures over 600°C without losing its temper, and it handles wood, light metals, PVC, and most shop-floor jobs. This is the cheapest option and the most forgiving for beginners.

Cobalt (HSS + 5–8% Cobalt) is the upgrade when you hit stainless or hardened steel. The cobalt binds with the HSS to keep the edge rigid and heat-resistant even as the bit ages. For tough metal drilling, Cobalt is the point-and-shoot answer. If you need a reliable set for frequent hard steel projects, our tested roundup of the best drill bits for hardened steel covers the current top options.

Carbide-tipped bits aren’t solid carbide — they have a carbide tip bonded to a steel body. Carbide is the hardest common metal, and these bits laugh at concrete, brick, stone, tile, and masonry. They don’t rust, and they stay sharp far longer than HSS, but they are brittle. Dropping one can chip the tip.

Diamond-coated bits use diamond particles bonded to the cutting edge. They are the only choice for glass, ceramic tile, and mineral-based materials where even carbide would chip the workpiece. The coating has a “one-and-done” lifespan — once it wears through, the bit is finished, but that lifespan is long enough for most home jobs.

Material-Specific Tip Selection Table

How To Sharpen A Dull Drill Bit At Home

Sharpening a worn bit restores its cutting geometry, but only if you preserve the original relief angle. The GIA Bench Tip method is the most straightforward documentation available.

Start by inserting a silicon carbide separating disk into a flex shaft hand piece. Secure the worn bit in a screw mandrel and brace it against the bench pin. Position the bit so you can file the relief area, then carefully lower the disk to barely touch the surface. Rotate the bit in the holding device without changing the angle, and repeat on the opposite relief plane. Hone the cutting edges by removing a small amount of metal from each surface, maintaining the ~60° cutting surface angle. The lip-to-web chisel point should sit around 135° when you’re done. Two evenly browned cutting lips will produce two chips of equal size — that is the success cue.

Common Mistakes That Ruin The Job

Walking on metal: A 118° bit on steel will skate across the surface unless you use a center punch to make a starting dimple. Switching to a 135° split-point bit solves this in many cases because the flatter angle catches without the punch.

Heat buildup: Drilling steel or aluminum dry generates friction heat that softens the tip and dulls it fast. Use cutting oil or lubricant for metals; drill slower for tough materials, faster for soft ones.

Long chip strands in aluminum: Ductile materials produce long ribbon chips that wrap around the bit and clog the flutes. If the tip geometry doesn’t support chip breakage, switch to a bit with a steeper helix angle (34°–38°) designed for aluminum.

Skipping the pilot hole: Flatter 135° points sometimes still need a pilot hole in dense material to prevent wandering. A smaller HSS bit at 118° followed by the finished 135° bit is often the cleanest sequence.

Quick Reference For CNC Drill Geometries

If you’re using a drilling center or CNC machine, the helix angle matters alongside the point angle. Low helix (12°–22°) is right for cast iron and brass because it keeps chips short. High helix (34°–38°) works for aluminum and plastics because it clears long chips quickly and prevents packing in deep holes.

Buying Guide: What To Look For Per Bit

The price range is wide: HSS bits can run under $1 each, Cobalt and Carbide bits land between 2–5 dollars per bit for solid quality. Brand names like Irwin, Milwaukee, and Bosch all produce bits that meet the 118° and 135° standards, so you aren’t paying for unique geometry — you are paying for consistent grinding, tip material, and coating quality. For the toughest steel jobs, the material and point angle matter more than the brand badge on the shank.