ENGINEERING REFERENCE CHART
CNC Material Machinability Chart
This machinability chart ranks 50+ metals and engineering plastics by how easily they machine — from free-cutting brass at 120% to Waspaloy at 10%. Every rating is relative to the industry baseline: AISI 12L14 free-machining steel at 100%.
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50+ Metals & Plastics Rated
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Cutting Speed & Tooling Guidance
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Cost-Per-Part Translation
Machinability Ratings
Relative to AISI 12L14 (100%)
120%
Free-cutting brass
100%
AISI 12L14 baseline
50%
Stainless steel 304
10%
Waspaloy
Cost translation: 22% vs 270%
Machinability · Speed · Tool Life
MATERIAL SCIENCE
What Is a Machinability Rating?
A machinability rating is a percentage that tells you how easily a material cuts compared to a reference standard. The standard is AISI 12L14 free-machining steel, assigned a rating of 100%.
Every other material’s rating is relative to that baseline: 200% means the material machines twice as fast as 12L14 with equivalent tool life. 50% means it runs at half the speed or produces the same amount of tool wear in half the time. The rating is a practical, shop-floor number with direct implications for cycle time, tooling cost, and part price.
Rating Baseline
AISI 12L14 free-machining steel is the industry reference at 100%. It contains lead and sulfur for chip-breaking, producing short chips, low tool wear, and predictable cutting forces — the standard against which all other materials are compared.
Real-World Meaning
A 50% material run at its optimal speed will wear a tool to a defined flank-wear limit in the same number of minutes that 12L14 does. Run it at 12L14’s speed and tool life drops to roughly 25% of baseline — the rating has direct practical consequences.
Cost Impact
Machinability rating translates directly to cycle time and tooling cost. A 50% material takes twice as long to machine or requires twice the tooling cost per part compared to a 100% material. The chart above includes cost translation data for every material.
MACHINING REFERENCE DATA
CNC Material Machinability Chart — 50+ Metals & Plastics Rated
Compare machinability ratings across 50+ engineering materials using reference data derived from production experience and standardized tool-life testing. All ratings relative to AISI 12L14 baseline at 100%.
Machinability ratings are production-proven values based on real CNC machining data. A 50% material takes twice as long to machine or wears tools twice as fast as 12L14. Use these values for cost estimation and process planning.
| Material Group | Grade / Alloy | Machinability Rating | Recommended Tool | Cutting Speed (SFM) |
|---|---|---|---|---|
| Aluminum | 6061-T6 | 250% | Carbide — 3 flute | 600–1200 |
| Aluminum | 7075-T6 | 220% | Carbide — 3 flute | 500–1000 |
| Brass | 360 (free-cutting) | 120% | Carbide / HSS | 400–800 |
| Copper | 101 (OFC) | 85% | Carbide — sharp edge | 300–600 |
| Carbon Steel | 1018 (hot rolled) | 70% | Carbide — TiN coated | 250–400 |
| Carbon Steel | 1045 (medium carbon) | 60% | Carbide — TiCN coated | 200–350 |
| Alloy Steel | 4140 (hardened, 34 HRC) | 50% | Carbide — AlTiN coated | 150–250 |
| Alloy Steel | 4340 (hardened, 36 HRC) | 45% | Carbide — AlTiN coated | 120–220 |
| Stainless Steel | 303 (free-machining) | 60% | Carbide — TiAlN coated | 150–300 |
| Stainless Steel | 304 / 316 (annealed) | 35% | Carbide — TiAlN coated | 80–180 |
| Stainless Steel | 17-4 PH (H900) | 30% | Carbide — AlTiN coated | 60–150 |
| Tool Steel | A2 (hardened, 58 HRC) | 25% | Carbide — AlTiN coated | 50–120 |
| Tool Steel | D2 (hardened, 60 HRC) | 20% | Carbide — AlTiN + ceramic | 40–100 |
| Titanium | Ti-6Al-4V (annealed) | 22% | Carbide — AlTiN coated | 80–150 |
| Nickel Alloy | Inconel 718 (aged) | 12% | Ceramic / carbide — AlTiN | 40–80 |
| Nickel Alloy | Waspaloy | 10% | Ceramic / carbide — AlTiN | 30–60 |
| Plastic | Acetal (POM) | 270% | Carbide — polished | 400–800 |
| Plastic | Nylon (PA6) | 230% | Carbide — polished | 300–700 |
| Plastic | PEEK (unfilled) | 180% | Carbide — polished | 250–500 |
| Plastic | ABS | 200% | Carbide — polished | 300–600 |
Tool Life & Cost Translation
A material rated 50% produces tool life exactly half that of 12L14 at its optimal speed. At 12L14 speeds, tool life drops to ~25% of baseline. Use these ratings to estimate tooling cost per part and compare material economics before selecting a grade.
Production-Proven Data
Ratings reflect actual production experience across 30+ CNC machines, not just handbook values. Speeds and tool recommendations are starting points — optimize based on your specific machine rigidity, toolholder, and coolant setup.
MACHINING PHYSICS
Why Machinability Varies: The Physics Behind the Numbers
Every number in this machinability chart has a physical cause. Four interacting properties explain why aluminum cuts like butter while Inconel eats tooling for breakfast.
01
Thermal Conductivity
Aluminum: 167 W/m·K. Titanium: 6.7 W/m·K. Aluminum chips carry ~70% of heat away; titanium only 25% — the rest hits the tool edge at 900–1,100°C. Carbide softens at 800°C.
02
Work Hardening
304 stainless converts austenite into harder martensite during cutting. A half-second dwell hardens the spot. Next pass chips or wears the tool. Solution: constant feed, sharp carbide, flood coolant.
03
Chip Formation
12L14 and C360 produce short, self-breaking chips. 5052 and 316 produce continuous, stringy chips that wrap tools and mar surfaces. Chip character matters as much as the rating.
04
Abrasive Inclusions
Cast irons contain hard carbides. Titanium’s α+β microstructure is abrasive. Inconel has intermetallic phases. These inclusions physically scratch the tool flank, accelerating wear.
Example: Why 304 Stainless Fights Back
304 stainless undergoes strain-induced martensitic transformation — cutting converts austenite into harder martensite at the cut surface. A half-second dwell creates a hardened spot that chips the next cutting edge. The physics explains why stainless needs sharp tools, constant feed, and aggressive coolant.
Thermal
6.7 W/m·K (Ti)
Hardening
304 → Martensite
Solution
Coolant + Constant Feed
MATERIAL REFERENCE
Machinability Drivers by Material Group
The dominant physical property that determines cutting behaviour for each common material family. Adjust strategy accordingly.
| Material Group | Dominant Driver | Effect on Cutting | Mitigation Strategy |
|---|---|---|---|
| Aluminum | Thermal Conductivity | High heat removal → fast cutting | High speeds, polished carbide, 3-flute |
| Copper / Brass | Chip Formation | Short chips (brass) vs gummy (copper) | Sharp tools, coolant, avoid dwell |
| Steel (1018, 1045) | Abrasive Inclusions | Flank wear from carbide precipitates | TiN/TiCN coating, moderate speeds |
| Alloy Steel (4140, 4340) | Hardness | High cutting forces, edge chipping | AlTiN coating, reduced speeds, rigid setup |
| Stainless Steel | Work Hardening | Surface hardens during cut | Constant feed, positive rake, flood coolant |
| Titanium | Thermal Conductivity | Heat stays in tool zone | High-pressure coolant, reduced speed, AlTiN |
| Nickel Alloys | Thermal + Abrasive | Extreme heat + hard carbides | Ceramic / carbide, low speed, rigid machine |
| Plastics (POM, PEEK) | Thermal Softening | Melts if heat builds | Sharp tools, high speeds, chip evacuation |
Machinability vs. Cost: What Each Rating Tier Costs You
The machinability rating does not just describe how easily a material cuts — it describes how much more machining time and tooling cost a given part will incur compared to a 6061-T6 aluminum baseline.
| Machinability Tier | Rating Range | Example Materials | Relative Machining Time* | Relative Tooling Cost* | Relative Total Machining Cost* |
|---|---|---|---|---|---|
| Excellent | ≥200% | 2011 Al, 6061 Al, C360 Brass | 0.5–1.0× | 0.5–1.0× | 0.5–1.0× (baseline = 6061) |
| Very Good | 100–199% | 12L14, 1215, 11L17 | 1.0–1.5× | 1.0–1.5× | 1.0–1.5× |
| Good | 65–99% | 1018, 1144, 303 SS, 416 SS | 1.5–2.5× | 1.5–2.0× | 2–3× |
| Moderate | 40–64% | 1045, 4140, 304 SS, 17-4PH | 2.5–4.0× | 2.0–3.0× | 3–6× |
| Difficult | 20–39% | 316 SS, D2, Ti CP, Monel 400 | 4.0–8.0× | 3.0–5.0× | 5–10× |
| Very Difficult | <20% | Ti-6Al-4V, Inconel, Hastelloy, Waspaloy | 8.0–15.0× | 5.0–10.0× | 10–20× |
*Relative to 6061-T6 aluminum: A material in the “Very Difficult” tier can cost 10 to 20 times more to machine than the same part in 6061 aluminum. Use these multipliers for cost estimation, supplier comparisons, and material selection trade-offs.
MACHINABILITY BASELINE
The 12L14 Baseline — What 100% Means
12L14 is a resulfurized and leaded low-carbon steel designed specifically for machinability. Every other material in this machinability chart is compared to it.
The lead (0.15–0.35%) acts as an internal lubricant at the cutting edge, promoting chip breaking and reducing built-up edge. The sulfur (0.26–0.35%) forms manganese sulfide inclusions that shear easily, producing short, discontinuous chips instead of long, stringy ribbons. Together, lead and sulfur make 12L14 the reference for what “easy machining” looks like in steel.
0.15–0.35%
Lead Content
Acts as an internal lubricant at the cutting edge, promoting chip breaking, reducing friction, and minimizing built-up edge formation on the tool rake face.
0.26–0.35%
Sulfur Content
Forms manganese sulfide inclusions that shear easily during cutting, producing short, discontinuous chips that clear the cut zone quickly and reduce tool contact time.
100%
Machinability Rating
The reference standard for steel machinability. Materials rated above 100% cut faster or with longer tool life. Materials rated below 100% require slower speeds, shorter tool life, or both.
Why This Matters for Your Parts
When a material is rated 50% versus 12L14’s 100%, it does not mean the part takes twice as long to machine in all cases — but it does mean the material removes chip volume at roughly half the rate at equivalent tool life. For high-volume production, the difference between 12L14 and a 50% material can be the difference between a part that is profitable and a part that loses money per piece. This is why the machinability rating is the first number a manufacturing engineer checks when evaluating material selection.
100%
12L14 Baseline
Lead + Sulfur
Chip-breaking additives
Cost Factor
Reference for pricing
MACHINABILITY QUESTIONS
Frequently Asked Questions
A machinability rating compares cutting ease to AISI 12L14 free-machining steel at 100%. A 200% material machines twice as fast; a 50% material runs at half speed or wears tools twice as fast. The rating predicts cycle time and tooling cost directly.
C360 brass (120%) is the fastest metal on the chart. 2011-T3 aluminum (310%) is the fastest on the non-ferrous scale. Delrin (acetal/POM) is the easiest plastic — it holds tighter tolerances than most metals but has a low max operating temperature.
304 work-hardens — cutting transforms surface austenite into harder martensite. Low thermal conductivity concentrates heat at the tool tip. Requires sharp positive-rake carbide, rigid setups, flood coolant, and continuous feed. Never dwell.
Aluminum ranges from 200% to 310%. 2011-T3 (310%) is the fastest screw-machine grade. 6061-T6 (270%) is the general-purpose standard. 7075-T6 (240%) is slightly more abrasive. 5052-H32 (200%) is prone to built-up edge. All machine faster than steel.
Lower rating increases cycle time and tooling consumption. 304 stainless (45%) costs 3–6× more than 6061 aluminum (270%). Inconel 718 (18%) costs 10–20× more. Machining time dominates total part cost — material price is often the smaller number.
Delrin (acetal/POM) is the easiest — it produces clean-breaking chips, machines dry, holds ±0.001″ tolerances, and wears tools minimally. Nylon is good but requires sharp tools and dry stock. PEEK is moderately difficult with higher heat and forces.
Waspaloy (≈10%) is among the most difficult. Inconel 718 (18%), Hastelloy C-276 (15%), hardened D2 (27%), and Ti-6Al-4V (22%) follow. All combine low thermal conductivity, high hot strength, work-hardening, and abrasive carbide formers.
From Aluminum to Inconel: We Machine Every Material in This Chart
This machinability chart exists because the material you choose determines everything downstream — cycle time, tooling cost, achievable tolerance, surface finish, and the final price on your quote. Baetro’s CNC programmers apply the data in this chart to every job, selecting the right tooling, coating, speeds, and coolant strategy for the specific material on the setup sheet.