Steel and aluminum alloy are the most widely processed metal materials in CNC machining. Their differences in hardness, ductility, thermal conductivity and chip forming characteristics lead to completely matched cutting speeds, feed rates and cutting depths for milling cutters. Improper parameter setting will cause serious tool wear, chipping, built-up edge, poor workpiece surface finish and dimensional deviation. This guide classifies solid carbide end mills for steel and aluminum, sorts out complete parameter matching rules, and provides adjustment schemes for different processing conditions to guarantee high precision, high efficiency and long tool life machining.

1. Material Machining Characteristic Difference Analysis

1.1 Carbon steel / alloy steel (45#, 40Cr, S136, P20)

Medium hardness, low thermal conductivity, high cutting heat accumulation; chips have moderate toughness, easy to form built-up edge on cutting edges under high temperature; high cutting impact during rough milling, requiring tools with high hardness and good toughness. Excessive cutting speed will accelerate coating oxidation wear, while too low feed will cause work hardening on the machined surface.

1.2 Aluminum alloy (6061, 6063, 7075 cast aluminum)

Low hardness, strong ductility, excellent thermal conductivity; soft chips are easy to stick to the cutter edge to form sticky aluminum; low cutting force, but high friction adhesion. Too high feed speed will produce burrs on the edge of the workpiece, and insufficient chip removal space will cause chip extrusion to scratch the finished surface.

2. Key Parameter Definition & Basic Matching Principles

Core parameters include cutting speed (Vc), spindle speed (S), feed per tooth (fz), axial cutting depth (ap), radial cutting width (ae). General matching principles:

For steel: Medium Vc, moderate fz, control single cutting load to avoid thermal wear and impact chipping;

For aluminum alloy: High Vc, large fz, large chip flute space, sufficient coolant to eliminate aluminum adhesion;

Rough machining: Increase ap and ae to improve material removal efficiency, properly reduce Vc to extend tool life;

Finishing machining: Reduce cutting depth, raise Vc and stabilize fz to lower surface roughness and guarantee dimensional precision.

3. Standard Parameter Matching for Steel Milling

Tool type: AlTiN coated solid carbide end mill, 2/4 flutes, sharp edge honing 0.02~0.05mm

3.1 Medium carbon steel 45# rough milling

Vc: 120–180 m/min; fz: 0.08–0.15 mm/z; ap ≤ 1.5D; ae ≤ 0.7D; coolant: full flood extreme pressure cutting fluid

3.2 Alloy steel 40Cr / mold steel P20 rough milling

Vc: 80–130 m/min; fz: 0.06–0.12 mm/z; ap ≤ 1D; ae ≤ 0.5D; reduce cutting speed to resist high temperature wear

3.3 Pre-hardened mold steel S136 finishing milling

Vc: 150–220 m/min; fz: 0.03–0.06 mm/z; ap ≤ 0.3D; ae ≤ 0.2D; tiny edge load to obtain mirror surface

3.4 Hardened steel (HRC 40–50) high precision finishing

Ultra-fine grain carbide tool; Vc: 60–100 m/min; small fz 0.02–0.04 mm/z; shallow cutting depth to prevent edge chipping

4. Standard Parameter Matching for Aluminum Alloy Milling

Tool type: Uncoated or DLC coated high polished aluminum special milling cutter, large chip flute, sharp edge without honing

4.1 6061/6063 aluminum rough milling

Vc: 1800–3500 m/min; fz: 0.15–0.35 mm/z; ap ≤ 2D; ae ≤ 0.8D; high flow oil mist or alcohol cutting fluid to avoid aluminum sticking

4.2 High-strength aviation aluminum 7075 rough machining

Vc: 1200–2500 m/min; fz: 0.12–0.28 mm/z; properly lower speed due to higher silicon content and abrasion

4.3 Aluminum thin-wall part precision finishing

Vc: 2200–4000 m/min; fz: 0.08–0.15 mm/z; ultra-shallow ap and ae, low cutting force to prevent workpiece deformation; climb milling mode recommended

4.4 Cast aluminum with silicon content ≥10%

Silicon particles cause abrasive wear; reduce Vc by 30% compared with wrought aluminum, add anti-abrasion DLC coating on tools

5. Process Mode Parameter Adjustment Rules

5.1 Climb milling vs conventional milling

Climb milling: Suitable for finishing aluminum and low-hardness steel, smaller tool vibration, better surface quality, can appropriately increase feed;

Conventional milling: For roughing high-hard steel, reduce fz by 20% to avoid impact edge collapse.

5.2 Dry cutting & wet cutting difference

Steel dry cutting: Vc reduce by 40%, fz reduce by 30% to control cutting temperature;

Aluminum dry cutting is not recommended; oil mist lubrication is mandatory to remove built-up aluminum.

5.3 Long overhang deep cavity machining

Tool overhang length ≥3D: Cutting speed decrease 25%–50%, feed reduce 30% to restrain vibration and dimensional jitter.

6. Common Machining Defects & Parameter Correction Solutions

6.1 Tool rapid flank wear when cutting steel: Vc too high or insufficient coolant; lower cutting speed and increase coolant flow rate.

6.2 Cutter edge chipping during steel roughing: Excessive ap/ae or too large fz; reduce single cutting depth and feed per tooth.

6.3 Aluminum sticking severely on cutter: Vc too low, poor tool polishing; raise cutting speed, switch to DLC polished aluminum cutter.

6.4 Aluminum thin wall deformation, dimensional tolerance out of range: Overlarge cutting load; adopt layered shallow cutting and lower feed speed.

6.5 Workpiece surface with obvious vibration ripples: Unmatched high speed feed, long tool overhang; reduce spindle speed and optimize feed parameters.

7. Auxiliary Matching Optimization to Improve Precision & Tool Life

1. Tool clamping: Use high-precision hydraulic collet or shrink fit holder to minimize runout, runout less than 0.003mm for finishing;

2. Chip removal: Aluminum processing uses large-flute 2-flute cutters; steel finishing selects 4-flute tools for stable cutting;

3. Coolant matching: Steel uses extreme pressure water-based cutting fluid; aluminum adopts low-viscosity special aluminum cutting oil or alcohol mist;

4. Tool coating selection: Steel processing AlTiN high temperature resistant coating; aluminum DLC anti-adhesion coating.

Conclusion

The core of parameter matching for high precision CNC milling cutters is to distinguish the physical properties of steel and aluminum alloy, and adjust cutting speed, feed per tooth and cutting depth according to rough/finish machining, material hardness and tool overhang length. Reasonable parameter coordination can effectively control tool wear, eliminate built-up edge, reduce machining vibration and workpiece deformation, stabilize dimensional tolerance and surface roughness, and realize efficient, low-cost and high-precision long-term batch CNC processing of steel and aluminum workpieces.