# Drill Cutting Speed Calculator

Calculate drill cutting speed (SFM or m/min) and spindle RPM from drill diameter and material. Machinery's Handbook values for HSS and carbide drills in 11 materials.

## What this calculates

Drill cutting speed is the velocity of the drill's outer cutting edge across the workpiece, measured in surface feet per minute (SFM). This calculator pulls Machinery's Handbook values for 11 common materials, applies the standard RPM = (SFM x 12) / (pi x D) equation, and returns spindle RPM for the drill size you enter. Works for both HSS and carbide drills, imperial or metric.

## Inputs

- **Drill Diameter** (in) — min 0.001 — Drill bit cutting diameter.
- **Workpiece Material** — options: Aluminum (300/800 SFM), Mild steel / 1018 (80/250 SFM), Alloy steel / 4140 (60/180 SFM), Stainless steel (40/130 SFM), Cast iron (60/200 SFM), Brass (200/400 SFM), Bronze (100/250 SFM), Copper (150/350 SFM), Titanium (25/80 SFM), Tool steel (50/150 SFM), Plastic (400/1000 SFM) — Material being drilled. SFM values shown as HSS/carbide.
- **Drill Material** — options: HSS (high-speed steel), Solid carbide — HSS is the default for general shop drilling. Solid carbide runs 2-3x faster but requires a rigid setup.
- **SFM Override** (SFM) — min 0 — Optional. Enter a specific SFM to override the material table.

## Outputs

- **Cutting Speed** (SFM) — Surface feet per minute for the drill and material combination.
- **Cutting Speed (metric)** (m/min) — Vc = SFM x 0.3048.
- **Spindle RPM** (RPM) — RPM = (SFM x 12) / (pi x D).
- **Surface Velocity** (ft/s) — Useful cross-check: SFM / 60.

## Details

Drill cutting speed formula

Two equations:

  - SFM (target cutting speed) is pulled from a material table. Aluminum is 300 SFM with HSS, 800 with carbide. Mild steel is 80 SFM with HSS, 250 with carbide.

  - RPM = (SFM x 12) / (pi x D) where D is the drill diameter in inches.

For a 1/4 inch HSS drill in mild steel at 80 SFM: RPM = (80 x 12) / (pi x 0.25) = 1,222 RPM. For a 1/2 inch HSS drill in aluminum at 300 SFM: RPM = (300 x 12) / (pi x 0.5) = 2,292 RPM.

Why drills run slower than end mills

A drill runs at about 75 percent of end-mill SFM in the same material. Three reasons: (1) coolant cannot reach the cutting edge at the tip, so heat builds up; (2) chip evacuation is harder in a hole than on an open face, so chips recut; (3) the drill point has a low relative velocity near the web, meaning the center rubs rather than cuts. All three combine to make drilling hotter than milling at the same SFM.

Drill cutting speed table

  
    MaterialHSS drill SFMCarbide drill SFM
  
  
    Aluminum300800
    Mild steel (1018)80250
    Alloy steel (4140)60180
    Stainless steel40130
    Cast iron60200
    Brass200400
    Titanium2580
    Plastic4001000
  

Handheld drill vs mill drill press vs CNC

The formula does not care about the machine, but your setup does. A handheld cordless drill cannot reach 1200 RPM on a 1/4 inch bit in steel, so drop SFM or use a smaller bit. A benchtop drill press usually tops out at 3000 RPM, adequate for 3/16 and larger HSS drills in steel. CNCs and VMCs can hit 8000 to 20000 RPM, more than enough for small drills. If the calculated RPM exceeds your spindle max, cap it there and accept the lower SFM.

Feed rate pairs with cutting speed

Cutting speed is half of the drilling recipe. Feed rate is the other half, specified in inches per revolution (IPR) and scaled to drill diameter. For a 1/4 inch drill in mild steel at 1,222 RPM with 0.0045 IPR feed, feed rate = 1,222 x 0.0045 = 5.5 IPM. See the drill feed rate calculator for the full feed equation.

## Frequently Asked Questions

**Q: How do I calculate drill cutting speed?**

A: SFM is looked up from a material table (80 SFM for HSS in mild steel, 250 for carbide). Then RPM = (SFM x 12) / (pi x D), where D is the drill diameter in inches. For a 1/4 inch HSS drill in mild steel, RPM = (80 x 12) / (pi x 0.25) = 1,222 RPM. This drill cutting speed calculator does both steps in one entry.

**Q: What speed should I drill steel at?**

A: For HSS drills in mild steel, 80 SFM. A 1/4 inch drill runs at 1,222 RPM, a 1/2 inch at 611 RPM, a 3/4 inch at 407 RPM. Carbide drills run 3x faster (250 SFM). Drop SFM 20-30 percent for alloy steel (4140) and 50 percent for stainless.

**Q: Why does drill cutting speed use diameter in the denominator?**

A: Cutting speed is tangential velocity at the drill's outer edge, which equals pi x D x RPM. If you want a fixed SFM, RPM has to scale inversely with diameter. A 1/4 inch drill spins 4x faster than a 1 inch drill at the same SFM because the outer edge has 4x less circumference to sweep per revolution.

**Q: Can I use this drill cutting speed calculator for metric drills?**

A: Yes. Enter the drill diameter in millimeters via the unit toggle. The calculator returns SFM (imperial) and m/min (metric) cutting speeds, plus RPM which is unit-independent. A 6 mm HSS drill in mild steel at 80 SFM runs at about 1,293 RPM.

**Q: What is the difference between drill cutting speed and feed rate?**

A: Cutting speed is the velocity of the cutting edge (SFM, which sets RPM). Feed rate is how fast the drill advances into the material (IPM, from RPM x IPR). Speed controls heat and tool wear; feed controls chip thickness and hole quality. Both have to be right for the drill to last.

**Q: Do handheld cordless drills matter here?**

A: The formula holds, but a cordless drill runs at 400-1500 RPM no-load. For a 1/4 inch HSS drill in mild steel you want 1,222 RPM, which most cordless drills can hit. For a 1/8 inch drill you need 2,445 RPM, which is out of reach. Use the calculator to spot these limits before you start the hole.

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Source: https://vastcalc.com/calculators/physics/drill-cutting-speed
Category: Physics
Last updated: 2026-04-08