Material Removal Rate by Spindle Power
Power-limited material removal rates for eight CNC alloys on 10 and 20 kW spindles, with the unit-power table, published benchmarks and a worked example.
Roughing MRR capacity at 10 and 20 kW spindle power (power-limited, calculated)
| Material and condition | K_p used (kW per cm³/s) | 10 kW turning (cm³/min) | 10 kW milling, cycle avg (cm³/min) | 20 kW turning (cm³/min) | 20 kW milling, cycle avg (cm³/min) |
|---|---|---|---|---|---|
| Aluminum 6061-T6 (wrought, ~95 HB) | 0.76–0.90 | 425–505 | 340–405 | 850–1,010 | 680–810 |
| Aluminum 7075-T6 (wrought, ~150 HB) | 0.76–0.90 | 425–505 | 340–405 | 850–1,010 | 680–810 |
| Carbon steel 1045 (190–220 HB) | 1.70–2.32 | 165–225 | 130–180 | 330–450 | 260–360 |
| Alloy steel 4140 (Q&T, 280–320 HB) | 2.18–3.29 | 115–175 | 90–140 | 230–350 | 180–280 |
| Stainless 304 (annealed, 150–180 HB) | 1.64–2.94 | 130–235 | 105–190 | 260–470 | 210–380 |
| Stainless 316 (annealed, 150–180 HB) | 1.64–2.94 | 130–235 | 105–190 | 260–470 | 210–380 |
| Titanium Ti-6Al-4V (annealed, 330–350 HB) | 1.65–1.77 | 215–230 | 170–185 | 430–460 | 340–370 |
| Brass C36000 (free-cutting, 90–120 HB) | 0.82–1.90 | 200–465 | 160–370 | 400–930 | 320–740 |
What Metal Removal Rate Can a 10 kW CNC Machine Achieve in Aluminium?
A 10 kW spindle can drive 425–505 cm³/min in 6061-T6 roughing at the 75% load this table assumes; a 40-taper VMC typically sustains 245–410 cm³/min in aluminium with HSM toolpaths. The gap between the two is cutter and chip-evacuation limits, not spindle power.
| Source | Machine / case | Material | MRR (cm³/min) | Note |
|---|---|---|---|---|
| S5 | 40-taper VMC, stable roughing | Carbon steel | 50–100 | 3–6 in³/min in the source |
| S5 | 40-taper VMC, HSM strategy | Aluminum | 245–410 | 15–25 in³/min in the source |
| S5 | 50-taper / horizontal | Steel | 100–200 | About double the 40-taper figure |
| S6 | 120 kW, 27,000 rpm (DST Ecospeed) | Aluminum 7050 | 5,160 | Competitor PCD tooling, case 1 |
| S6 | 120 kW, 27,000 rpm | Aluminum 7050 | 7,465 | RAL90 coating, same case |
| S6 | 120 kW, 33,000 rpm (Makino MAG 3.W) | Aluminum (cutter diameter 50 mm) | 7,000 | 420,000 cm³ removed in 60 min |
| S8 | Bridgeport 2 hp / HAAS 30 hp comparison | Aluminum | 165 | 10.1 in³/min at 1.1–3.0 kW cutting power |
How Much Slower Is 304 Stainless Than 6061 on the Same 10 kW Spindle?
About 2–4× slower: 130–235 cm³/min for 304 versus 425–505 cm³/min for 6061, because austenitic stainless needs 1.64–2.94 kW per cm³/s against 0.76–0.90 for aluminum. On the same 86 cm³/min cut that loads a 10 kW spindle to 15% in 6061, 304 draws 50%.
| Material | Condition | ISO | Hardness (HB) | K_p (kW per cm³/s) | Source (low / high) |
|---|---|---|---|---|---|
| Aluminum 6061-T6 | wrought, T6 | N | ~95 | 0.76–0.90 | S4 / S3 |
| Aluminum 7075-T6 | wrought, T6 | N | ~150 | 0.76–0.90 | S4 / S3 — take the upper end for 7075 |
| Carbon steel 1045 | hot-rolled / normalized | P | 190–220 | 1.70–2.32 | S2 (190 HB) / S3 (200–220 HB) |
| Alloy steel 4140 | quenched and tempered, 28–32 HRC | P | 280–320 | 2.18–3.29 | S3 (280–320 HB) / S4 (220–420 HB upper bound) |
| Stainless 304 | annealed | M | 150–180 | 1.64–2.94 | S3 (150–175 HB) / S4 (austenitic 150–275 HB) |
| Stainless 316 | annealed | M | 150–180 | 1.64–2.94 | S3 (150–175 HB) / S4 (austenitic 150–275 HB) |
| Titanium Ti-6Al-4V | annealed | S | 330–350 | 1.65–1.77 | S4 (300–360 HB) / S3 (Ti-150 A, 340 HB) |
| Brass C36000 | leaded free-machining | N | 90–120 | 0.82–1.90 | S3 / S4 — see the conflict register |
What MRR Should I Plan for 4140 Steel on a 10 kW Machine?
Plan 115–175 cm³/min in turning and 90–140 cm³/min as the milling cycle average for 280–320 HB 4140, and quote from the low end. The power ledger below shows why: the same 86 cm³/min cut that loads a 10 kW spindle to 15% in 6061 loads it to 55% in 4140. Parameters that give 86 cm³/min in aluminium do not transfer to steel — each material drops to its own cutting speed first, so the ledger compares power cost only.
| Material | K_p (kW per cm³/s) | P_c at the tool (kW) | P_spindle input (kW) | Load on a 10 kW spindle (%) |
|---|---|---|---|---|
| Aluminum 6061-T6 | 0.90 | 1.29 | 1.5 | 15 |
| Carbon steel 1045 | 2.32 | 3.33 | 3.9 | 39 |
| Alloy steel 4140 | 3.29 | 4.72 | 5.6 | 55 |
| Stainless 304 | 2.94 | 4.21 | 5.0 | 50 |
| Titanium Ti-6Al-4V | 1.77 | 2.54 | 3.0 | 30 |
| Brass C36000 | 1.90 | 2.72 | 3.2 | 32 |
Is Titanium Roughing Limited by Spindle Power?
No: Ti-6Al-4V needs only 1.65–1.77 kW per cm³/s, so a 10 kW spindle has a power ceiling of 215–230 cm³/min — heat and tool life limit the real cut long before the spindle does. Treat the titanium row as an upper-bound check, never as a target, and keep the high-pressure coolant the cutting-parameters table calls mandatory.
| Item | Value | How to read it |
|---|---|---|
| K_p (unit power) | 1.65–1.77 kW per cm³/s | Below 4140 — the spindle is not the bottleneck |
| 10 kW turning ceiling | 215–230 cm³/min | Power allows more than shops typically run |
| 10 kW milling ceiling, cycle avg | 170–185 cm³/min | Cycle average at the 80% in-cut factor |
| 20 kW turning ceiling | 430–460 cm³/min | Doubles the ceiling, not the allowable cut |
| Actual limiter | Heat and tool life | Run the cutting-parameters speeds with high-pressure coolant — the coolant is a precondition, not an option |
Does a 20 kW Spindle Double My Removal Rate?
It doubles the power ceiling — 850–1,010 cm³/min in 6061 — but only if the cutter and fixture can absorb it. In a 50 × 50 mm pocket with a Ø12 cutter, a 20 kW spindle changes nothing: the cutting time stays 17.5 s because the tool, not the spindle, is the constraint.
| Parameter | Ø12 cutter (worked example) | Ø20 cutter (illustrative) |
|---|---|---|
| Tool | Ø12 mm, 3-flute carbide end mill | Ø20 mm — an example, not a recommendation |
| Radial width a_e (mm) | 6 | 10 |
| Axial depth a_p (mm) | 6 | 10 |
| Feed speed V_f (mm/min) | 2,388 | 2,000 |
| MRR (cm³/min) | 86 | 200 |
| Cutting time for 25 cm³ | 17.5 s | 7.5 s |
Why Is Milling MRR Lower Than Turning on the Same Machine?
The cut is interrupted and the tool spends about 20% of the cycle not cutting, so the cycle-average milling rate is 0.8× the turning rate: 340–405 vs 425–505 cm³/min in 6061 on 10 kW. The instantaneous in-cut rate can still reach the turning figure.
| Step | Rule | 6061-T6, 10 kW |
|---|---|---|
| 1 | Turning ceiling: Q_max = 60 × 10 × 0.6375 / K_p, rounded to 5 cm³/min | 425–505 |
| 2 | Milling column = 0.8 × the rounded turning column, rounded to 5 cm³/min | 340–405 |
| 3 | 20 kW columns = 2 × the 10 kW columns (exact doubling) | 850–1,010 turning / 680–810 milling |
What Spindle Load Should I Target When Roughing?
70–85% of rated power; this table uses 75%, which leaves margin for tool wear and hardness variation. The fixed assumptions below are planning values — calculated, not measured — so if your shop measures drive efficiency at 0.80 or 0.90, scale the whole table proportionally.
| Parameter | Value | Basis |
|---|---|---|
| Rated spindle power P_rated | 10 / 20 kW | The two common VMC power classes |
| Drive efficiency η | 0.85 | Planning assumption, not a measurement — confirm against the machine tool builder data |
| Roughing load factor L | 0.75 | Midpoint of the 70–85% target band (S5) |
| Usable cutting-power factor | 0.85 × 0.75 = 0.6375 ≈ 0.64 | Only 0.64 kW of each rated kW reaches the chip |
| Tool condition | Sharp carbide | The K_p tables are compiled for sharp cutting tools |
| Milling in-cut factor | 0.80 | S5 worked example: 80% of the cycle in cut |
| Coolant and setup | Stable, no chatter | Steel and stainless flood emulsion; titanium high-pressure coolant; aluminum flood or MQL |
What Is the MRR Formula for Milling and Turning?
Milling: Q = a_e × a_p × V_f / 1,000. Turning: Q = V_c × f × a_p. Worked example: a 12 mm cutter at 6 × 6 mm engagement and 2,388 mm/min removes 86 cm³/min. The parameters are deliberately conservative — 0.10 mm per tooth against 0.15–0.19 for a Ø12 cutter in the cutting-parameters table — so every step stays checkable.
| Step | Quantity | Value |
|---|---|---|
| 1 | Removal volume V | 50 × 50 × 10 mm pocket = 25 cm³ |
| 2 | Tool and engagement | Ø12 mm, 3-flute carbide end mill; V_c 300 m/min; f_z 0.10 mm/tooth; a_e = a_p = 6 mm |
| 3 | Spindle speed n = 1,000 × V_c / (π × D) | 7,958 → take 7,960 rpm |
| 4 | Feed speed V_f = n × z × f_z | 7,960 × 3 × 0.10 = 2,388 mm/min |
| 5 | MRR Q = a_e × a_p × V_f / 1,000 | 6 × 6 × 2,388 / 1,000 = 85.97 → 86 cm³/min |
| 6 | Cutting time T = V / Q | 25 / 86 = 0.291 min = 17.5 s (21.8 s with 20% non-cutting) |
| 7 | Power check P_c = K_p × Q, spindle input P_c / 0.85 | 0.90 × 1.433 = 1.29 kW → 1.52 kW → 15.2% of 10 kW |
| 8 | Reading | Spindle only 15% loaded — the Ø12 cutter in a 50 mm pocket is tool-limited; the 425 cm³/min ceiling would need V_f 11,806 mm/min, five times beyond this cutter |
How Do I Convert MRR to Machining Time?
T = V / Q. A 50 × 50 × 10 mm pocket is 25 cm³, so at the example's 86 cm³/min the cutting time is 17.5 s — about 22 s once 20% non-cutting time (plunge, retract, layer changes) is added. Tool-change and inspection allowances come on top of that. The times below are T = 25 / Q for the same pocket, rounded to one decimal — calculated, not measured.
| Rate case | Q (cm³/min) | Time for 25 cm³ (s) |
|---|---|---|
| Worked example toolpath (Ø12 in 6061) | 86 | 17.5 |
| Ø20 cutter example | 200 | 7.5 |
| 6061 10 kW turning ceiling | 425 | 3.5 |
| 304 planning low end | 130 | 11.5 |
| 4140 milling planning low end | 90 | 16.7 |
How Accurate Are These MRR Numbers for Quoting?
Treat them as a ±25% planning band, not a guarantee: they assume sharp carbide, 85% drive efficiency and a stable setup. Published 120 kW aluminum cases reach 5,160–7,465 cm³/min — 43–62 cm³/min per kW — consistent with the linear scaling this table assumes. Where sources disagree, the conflicts stay registered and unresolved rather than averaged.
| Conflict | Source A | Source B | Handling on this page |
|---|---|---|---|
| 304 / 316 unit power | S3 handbook band 1.64–1.97 (150–200 HB, sharp tools) | S4 energy-study value 2.94 (austenitic 150–275 HB) | The full 1.64–2.94 band stays in the tables; quote from the 130 cm³/min low end unless hardness and tools are confirmed at the favorable end |
| C36000 unit power | S3 leaded brass 0.82 | S4 leaded brass 1.90 | 0.82 matches brass physics (K_p ≈ k_c / 1,000, k_c ≈ 800 N/mm²), so prefer the 0.82 end; the 200–465 band stays as the registered envelope |
| 1045 / 4140 ranges | S3 by 20 HB steps | S4 220–420 HB envelope | Not a conflict — the range tracks hardness; do not describe it as sources disagreeing |
How to Use These Numbers
- These columns are power-limited capacity, not typical MRR: published 40-taper benchmarks run 50–100 cm³/min in carbon steel against the 165–225 cm³/min 1045 ceiling, so quoting the ceiling as a typical rate overstates capacity 2–4×.
- Titanium and the austenitic stainless rows are tool-life limited, not power limited: 215–230 cm³/min for Ti-6Al-4V is an upper-bound check, while the achievable band is set by heat and tool life at the cutting-parameters speeds.
- Rounding convention: 10 kW columns are rounded to 5 cm³/min, milling columns are 0.8 × the rounded turning column (rounded to 5 again), and 20 kW columns are exactly double the 10 kW columns — the doubling in the table is precise.
- The 0.85 drive efficiency, the 0.75 roughing load and the resulting 0.64 usable-power factor are calculated planning assumptions, not measurements — if your shop measures different values, scale the table proportionally.
- Each K_p band spans published sources: the low end is the most power-frugal value, the high end the conservative one. Quote capacity from the low end — hardness at the top of the band, worn edges and thin chips all push K_p up.
- K_p (kW per cm³/s) is numerically k_c / 1,000; Sandvik tables publish k_c while spindle books publish K_p, and this page standardizes on K_p.
Frequently Asked Questions
425–505 cm³/min in 6061-T6 at the assumed 75% load; a 40-taper VMC typically sustains 245–410 cm³/min with HSM toolpaths.
About 2–4× slower: 130–235 cm³/min for 304 against 425–505 cm³/min for 6061, because 304 needs 1.64–2.94 kW per cm³/s against 0.76–0.90 for aluminum.
115–175 cm³/min in turning and 90–140 cm³/min as the milling cycle average for 280–320 HB 4140; quote from the low end.
No — Ti-6Al-4V needs only 1.65–1.77 kW per cm³/s, so the 10 kW power ceiling is 215–230 cm³/min; heat and tool life limit the real cut first.
It doubles the power ceiling (850–1,010 cm³/min in 6061), but only if cutter and fixture can absorb it; a Ø12 cutter in a 50 × 50 mm pocket gains nothing.
The tool spends about 20% of the cycle out of cut, so the milling column is 0.8× the turning column: 340–405 vs 425–505 cm³/min in 6061 on 10 kW.
70–85% of rated power; this table uses 75% to leave margin for tool wear and hardness variation.
Milling Q = a_e × a_p × V_f / 1,000; turning Q = V_c × f × a_p — a 12 mm cutter at 6 × 6 mm and 2,388 mm/min gives 86 cm³/min.
T = V / Q: a 50 × 50 × 10 mm pocket is 25 cm³, so 86 cm³/min cuts it in 17.5 s (about 22 s with 20% non-cutting time).
Use them as a ±25% planning band: they assume sharp carbide, 85% drive efficiency and a stable setup; published 120 kW aluminum cases reach 5,160–7,465 cm³/min, matching linear scaling.
Standards & Sources
- S1 — Sandvik Coromant, Specific cutting force: k_c1 definition, chip-thickness correction and the power formula
- S2 — Sandvik Coromant, Workpiece materials (MC code tables): P-group steel k_c1 values and the m_c exponent
- S3 — DynoSpindles, Application Engineering Data Part Two (Book of Spindles), Tables 5/9/10/11/12: K_p unit-power values for sharp carbide tools
- S4 — Kellens et al. (2012), UPLCI-CO2PE! Appendix II, Table MR1.2(a), Int. J. Life Cycle Assess. 17: 242–251: independent unit-cutting-energy cross-check
- S5 — MFG Calcs, Driving Material Removal Rate Without Burning Up Spindles: 40/50-taper shop benchmarks, the 70–85% spindle-load target and the 80% in-cut example
- S6 — Sandvik Coromant aerospace case C-1040-169: 120 kW aluminum machining at 5,160 / 7,465 / 7,000 cm³/min
- S7 — Rough Logic spindle-MRR calculator (unit-power values per Machinery Handbook): third-party cross-check
- S8 — MIT OCW 2.008 Lecture 7 (Cutting): specific cutting energy and a 165 cm³/min, 1.1–3.0 kW milling example
- S9 — Sinbo cutting-parameters table: the same eight materials, speeds and feeds these power ceilings plug into
- K_p (kW per cm³/s) equals k_c / 1,000 numerically; both notations are kept with their own sources
- All Q_max values are calculated from the K_p bands plus the fixed assumptions — calculated, not measured; the three shop-confirmation items of the source study (per-machine drive efficiency, the 4140 hardness band on hand, a dedicated 7075 K_p row) are pending shop data, not published values
Related Pages
- /wiki/reference/cutting-parameters/ — Sibling quick table: the speeds and feeds that turn these power ceilings into actual parameters
- /wiki/reference/material-density/ — Sibling quick table: density for the same eight materials
- /wiki/reference/thermal-expansion-coefficients/ — Sibling quick table: thermal expansion coefficients for the same materials