The Problem: One Angle Does Not Fit Every Metal
A drill bit point angle looks like a small detail, but it decides how the bit enters the material, how much thrust it needs and how cleanly the hole is formed. Use the wrong geometry and the bit skates across the surface, grabs in soft metal, or chips out the exit edge in cast iron.
Buyers who treat every job as "just a twist bit" end up with poor hole quality and wasted tooling.
Why It Happens: The Geometry Behind the Cut
The point angle is the included angle measured across the cutting lips. It controls two competing needs: penetration and strength.
- Narrow angles (90 to 118 degrees) bite aggressively and centre well, but the thin tip is weak.
- Wide angles (135 to 140 degrees) are stronger, self-centring and spread the load, making them better for harder or thin materials.
- Soft, gummy metals like aluminum grab a sharp narrow point and pull the bit in, while cast iron is brittle and chips at the exit if the point is too thin.
Standard off-the-shelf bits are usually 118 degrees; a split-point 135 degree bit is the modern default for precision work.
The Solution: Match the Point to the Material
- Mild and alloy steel: 118 degrees for general work, 135 degree split point when self-centring and low thrust matter. A 135 degree quick-cut DIN338 bit covers most steel jobs.
- Aluminum and soft metals: a 118 to 135 degree point with a polished flute sheds soft chips. A TiN coated DIN338 bit reduces built-up edge.
- Cast iron: a 135 degree point with a slightly blunt edge avoids digging and chipping the brittle surface. A Morse taper shank bit suits cast iron and structural steel on lathes and radial drills.
- Thin sheet: use a 135 degree split point or step drill to stop the tip grabbing as it breaks through.
Application: Reading the Job Before You Drill
On a drill press, a 135 degree split point removes the need for a pilot hole because it self-centres. In hand drilling, the same geometry reduces the force you must push, which keeps holes straight. For CNC work, point geometry works together with rigid tool holding and controlled feed to deliver consistent hole size.
Technical Reference: Point Angle Selection Table
| Material | Recommended point | Why |
|---|
| Mild / alloy steel | 118 or 135 degrees | Balanced strength and cut |
| Stainless steel | 135 degrees split | Low thrust, less work hardening |
| Aluminum / brass | 118 to 135 degrees | Prevents grabbing |
| Cast iron | 135 degrees | Resists edge chipping |
| Thin sheet / PVC | 135 degrees split | Clean breakthrough |
| Hard alloys | 135 to 140 degrees | Strong tip, high heat |
| Problem | Cause | Correction |
|---|
| Bit walks on start | Narrow, non-split point | Use 135 degree split point |
| Grabs in aluminum | Too sharp a point | Wider angle, slower feed |
| Chipped exit in cast iron | Thin point, heavy feed | Back up feed on breakthrough |
FAQ
Q: Is 135 degrees always better than 118?
A: Not always. 135 degrees is better for hard, thin or precision work; 118 degrees still cuts well and is cheaper for general soft steel.
Q: What does "split point" mean?
A: A secondary grind across the tip that creates a self-centring chisel edge and reduces thrust.
Q: Does point angle change drill speed?
A: It changes feed and thrust more than speed, but a stronger point tolerates slightly higher speeds in hard material.
Q: Can I regrind a bit to a different angle?
A: Yes, a competent tool grinder can change the point, but split-point geometry needs a specialist fixture.
Matching HSS Drill Bits to the Material in Front of You
The right point angle turns an average HSS drill bit into a precise one. Whether the job is steel, aluminum or cast iron, HSS drill bits perform best when their geometry is chosen for the material rather than inherited by habit. Standardise on the angles that suit the work in your shop, and HSS drill bits become a predictable part of every process.
Compare Point Geometries
Choose the geometry your material demands. Well-chosen HSS drill bits cut cleaner and last longer. Browse the HSS Drill Bit category to compare 118, 135 degree split point and step-drill options side by side.
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