Machining Tolerances and Surface Roughness of Aluminum Round Bars

Aluminum round bars are widely used in precision machinery and automation systems, thanks to their excellent machinability, strength-to-weight ratio, and dimensional stability. For components such as shafts, housings, and gears, both tight machining tolerances and a fine surface roughness are essential to ensure performance, longevity, and interchangeability.

Standard Tolerances for Aluminum Round Bars

The dimensional tolerances of aluminum bars are typically defined by ISO or ASTM standards, such as ASTM B221. Common tolerance classes include:

• H9 / h9 tolerance: For precision parts requiring close fits (±0.036 mm for 40 mm diameter)
• H11 / h11 tolerance: Used for general machining applications (±0.090 mm for 40 mm diameter)
• Custom tolerances: Available through centerless grinding or CNC turning for ultra-precise needs (±0.005 mm achievable)

Surface Roughness for Machined Aluminum Bars

Surface finish plays a vital role in wear resistance, assembly fit, and sealing performance. Typical surface roughness (Ra) values for aluminum round bars after machining are:

• Ra 3.2 µm: Standard turning or milling
• Ra 1.6 µm: Fine finishing or CNC lathe operations
• Ra 0.8 µm or lower: Achieved by polishing or grinding for ultra-smooth surfaces

Recommended Aluminum Alloys for Precision Machining

• 6061-T6 Aluminum Round Bar: Excellent strength and good machinability for shafts, brackets, and automation parts
• 2024-T4 Aluminum Round Bar: High strength and fatigue resistance for aerospace components
• 7075-T6 Aluminum Rod: Superior mechanical properties for critical high-load parts

Finishing Options to Improve Surface and Tolerance

To meet tight design specifications, aluminum round bars can undergo additional processes such as:

• Precision CNC turning and milling
• Centerless grinding for tolerance ≤ ±0.01 mm
• Anodizing or hard anodizing for surface hardness and corrosion resistance
• Superfinishing or polishing for mirror-like Ra ≤ 0.4 µm

Applications in Precision Machinery

High-tolerance aluminum bars are essential in:

• Linear motion shafts
• Robotic joints and arms
• Hydraulic valve bodies
• Sensor housings
• Optical and medical equipment frames

Get High-Precision Aluminum Round Bars

We offer aluminum round bars with tight machining tolerances and controlled surface roughness, available in various diameters and alloys. All bars are CNC-ready and meet international quality standards.

Contact us now for technical specifications, tolerance charts, and custom machining services for aluminum rods used in precision systems.

Author: frank

Chalco Aluminium is specialized in producing and marketing aluminium bar.Our customer service representatives are qualified,knowledgeable aluminum bars experts, Thire industry expertise and professionalism will save you time and money and ensure that you have the best aluminium bars and rods.