# Reamer Feed and Speed Calculator

Reamer feed and speed calculator. Enter reamer diameter, material, and flute count to get RPM, IPR, IPM feed rate, and SFM for HSS or carbide reamers across aluminum, steel, stainless, and more.

## What this calculates

Reaming is a finish-sizing operation, not a material removal operation, so it runs at roughly one-third of the SFM used for drilling the same material. Pushing a reamer too fast glazes the flutes and oversizes the hole; feeding too lightly chatters and leaves a chewed-up bore. This reamer feed and speed calculator returns spindle RPM, feed per flute, feed per revolution, and linear feed rate for HSS or carbide reamers across a full range of shop materials.

## Inputs

- **Reamer Diameter** (in) — min 0.001 — Nominal reamer diameter. Enter the finish hole size.
- **Workpiece Material** — options: Aluminum (150/400 SFM), Mild steel / 1018 (50/150 SFM), Alloy steel / 4140 (40/120 SFM), Stainless steel (30/90 SFM), Cast iron (50/150 SFM), Brass (130/300 SFM), Bronze (80/180 SFM), Copper (100/250 SFM), Titanium (20/60 SFM), Plastic / Delrin (200/500 SFM) — Pick the workpiece material. Reaming SFM is about a third of drilling SFM.
- **Reamer Material** — options: HSS (high-speed steel), Solid carbide — HSS reamers are the shop standard. Carbide reamers run 3x faster.
- **Number of Flutes** — min 2, max 16 — Typical chucking reamers are 4-6 flute. Even counts balance load on opposed edges.
- **Feed per Flute Override (IPT)** (in/flute) — min 0 — Optional. Leave at 0 to use a material default. Typical range 0.001-0.006 IPT.

## Outputs

- **Spindle Speed** (RPM) — Spindle RPM = (SFM x 12) / (pi x D).
- **Cutting Speed** (SFM) — Surface feet per minute for the chosen material and reamer.
- **Feed per Flute** (IPT) — Chip load per flute used in the feed rate calculation.
- **Feed per Revolution** (in/rev) — IPR = feed per flute x number of flutes.
- **Feed Rate** (in/min) — Linear feed rate in IPM = RPM x IPR.

## Details

The reamer feed and speed formulas

The same cutting speed equation that drives drilling and milling applies to reaming, scaled for the slower SFM a reamer expects.

  - RPM = (SFM x 12) / (pi x D) where SFM is surface feet per minute and D is reamer diameter in inches.

  - Feed rate (IPM) = RPM x IPR where IPR is feed per revolution.

  - IPR = feed per flute x flute count. Reamers use large feeds relative to drills because each flute only needs to shave a light chip.

For a 1/2 inch HSS 6-flute chucking reamer in mild steel at 50 SFM: RPM = (50 x 12) / (pi x 0.5) = 382 RPM. At 0.004 IPT per flute, IPR = 0.024 and feed rate = 382 x 0.024 = 9.17 IPM. Doubled or tripled feed rates are common on rigid CNC setups once the first hole proves the tool is cutting cleanly.

Reamer SFM reference

  
    MaterialHSS SFMCarbide SFM
  
  
    Aluminum150400
    Mild steel (1018)50150
    Alloy steel (4140)40120
    Stainless steel3090
    Cast iron50150
    Brass130300
    Titanium2060
    Plastic (Delrin)200500
  

Why reamers run so slow

A reamer is a precision tool that sizes and finishes a hole left slightly undersized by a drill or boring bar. Each flute removes a chip measured in tenths of a thousandth. Fast SFM builds heat faster than the thin chip can carry it away, and the heat softens the cutting edge and expands the hole diameter. Machinery's Handbook and the Cleveland Twist Drill reaming guide both recommend starting at half the drilling SFM and dialing up only if surface finish and hole size stay in tolerance.

Chucking, shell, and carbide reamers

A chucking reamer is the standard CNC reamer, typically 4-6 flute HSS. Shell reamers mount on an arbor and handle larger diameters (3/4 inch and up). Carbide reamers (solid or tipped) run 3x the HSS SFM and give excellent finish in hardened steels or stainless, but they chip easily if feed per flute is too high. For stainless, start at 0.0025 IPT, 30 SFM with HSS, and dial to 90 SFM with carbide only after the first hole proves clean.

## Frequently Asked Questions

**Q: How do I calculate feed and speed for a reamer?**

A: Use RPM = (SFM x 12) / (pi x D) where SFM is the cutting speed for your material (50 SFM for HSS in mild steel, 150 with carbide). Then feed rate (IPM) = RPM x IPR, where IPR equals feed per flute (0.002 to 0.006 typical) times the flute count. For a 1/2 inch 6-flute HSS reamer in steel: 382 RPM and 9.17 IPM.

**Q: What SFM should I run for a reamer in stainless steel?**

A: HSS reamers in 304 or 316 stainless run 30 SFM. Carbide reamers run 90 SFM. For a 1/4 inch HSS reamer at 30 SFM: RPM = (30 x 12) / (pi x 0.25) = 458 RPM. With a 4-flute reamer at 0.0025 IPT: feed rate = 458 x 0.010 = 4.58 IPM. Use good coolant; stainless work-hardens if the reamer stalls or rubs.

**Q: Why is reamer speed so much slower than drill speed?**

A: A drill removes gross material; a reamer shaves a finish chip of 0.004 inch or less per side. Running fast builds heat that glazes the cutting edges and oversizes the hole, both of which ruin the finish. Start at about one-third of the drilling SFM for the same material. This matches Machinery's Handbook and every reamer manufacturer's chart.

**Q: How much stock should I leave for reaming?**

A: Leave 0.005 to 0.015 inch on diameter for reamers under 1/2 inch, and 0.015 to 0.030 inch for reamers larger than 1 inch. Too little stock and the reamer rubs instead of cutting, glazing the flutes. Too much and the reamer deflects and oversizes or tapers the hole. The right prep drill size is the reamer OD minus the stock allowance.

**Q: Can I use this calculator for hand reamers?**

A: Yes, but ignore the RPM output. Hand reamers turn at whatever speed your wrist allows, usually 30-60 RPM. Use the feed-per-flute figure as a guide for how hard to push the reamer: about 0.002-0.004 IPT for steel and brass, 0.005-0.008 IPT for aluminum. Keep the reamer aligned with the hole and turn it in the cutting direction only.

**Q: What is the best feed per flute for a carbide reamer?**

A: Carbide reamers want light feeds: 0.001-0.003 IPT in hard materials, up to 0.004 IPT in aluminum. Carbide is brittle; a fat chip per flute chips the cutting edge. Start at the low end, run an inspection, and dial up only if the finish is poor. High-quality carbide reamers in hardened steel can hold 0.0002 inch hole tolerance at these feed rates.

---

Source: https://vastcalc.com/calculators/physics/reamer-feed-and-speed
Category: Physics
Last updated: 2026-04-08