SpecCalcsReference calculators for the shop floor

Cutting speed & RPM for Brass (free-machining)

Brass (free-machining) turns at roughly 500–1000 SFM with carbide (200–350 SFM with HSS). A 1/2″ tool then wants about 3800–7600 rpm — enter your own diameter below.

Surface-speed bands are starting points · tune to your tool coating, coolant and rigidity

Speed & feed calculator n = SFM·12/πD
Spindle speed
Spindle speed from surface speed
n=SFM×12π D  =  Vc×1000π Dmmn = \frac{\text{SFM} \times 12}{\pi \, D} \;=\; \frac{V_c \times 1000}{\pi \, D_{mm}}
n spindle rpm · SFM surface ft/min · Vc surface m/min · D tool or work diameter

Brass (free-machining) cutting speed — SFM by operation & tool

OperationHSS
SFM		Carbide
SFM
Turning200–350500–1000
Milling160–280400–800
Drilling120–210300–600

Turning is the baseline; milling ≈ 0.8×, drilling ≈ 0.6× (rule of thumb). Bands per Machinery’s Handbook and tool-maker charts — starting points, not limits.

These are starting speeds, not targets. Real surface speed depends on tool coating, coolant, setup rigidity and how the chip clears. Start mid-band, then push up while the finish, chip colour and tool wear stay healthy.

Machining Brass (free-machining)

Cuts fast and clean but can grab a positive-rake tool and climb into the work. A zero or slightly negative rake tames it.

How the RPM is worked out

Surface speed — SFM, or Vc in m/min — is the speed of the cutting edge past the work, and it is the number that actually protects tool life. Spindle rpm is just what that surface speed becomes once you fix the diameter: n = SFM × 12 / (π·D). Halve the diameter and the rpm doubles for the same surface speed, which is why a small drill spins so much faster than a face mill in the same material.

HSS vs. carbide

Carbide holds its edge hot, so it runs roughly three to six times the surface speed of HSS in Brass (free-machining) — the two columns above. HSS still earns its place on flexible setups, interrupted cuts and small-shop drilling, where its toughness beats carbide’s brittleness. Match the speed column to the tool actually in the holder, not the one you wish you were using.

Turning the feed into a number

Once you have the rpm, feed follows from chip load: feed = rpm × feed-per-tooth × flutes for milling. The calculator does this from the values you enter — pick a feed-per-tooth from your cutter’s data, then read the feed rate alongside the rpm.

Need chip-load numbers to set the feed? Brass (free-machining) feed rate & chip load

References

  1. Machinery’s Handbook — “Cutting Speeds and Feeds”: surface-speed tables by material and tool material.
  2. Tool-manufacturer speed & feed charts (grade- and coating-specific) — use these to refine the starting bands above.

Last reviewed: 2026-07 · Calculation method & assumptions