Stainless Steel Capillary Tube Specifications: Complete Guide to Sizes, Tolerances & Standards
Understanding Capillary Tube Specifications
Selecting the right stainless steel capillary tube requires understanding the key specifications including dimensions, tolerances, material grades, surface finishes, and applicable standards. This comprehensive guide covers everything you need to know about capillary tube specifications.
Dimensional Specifications
Outside Diameter (OD) Range
| Category | OD Range (mm) | OD Range (inches) | Typical Applications |
|---|---|---|---|
| Micro Capillary | 0.1 – 0.5 | 0.004 – 0.020 | Medical needles, microfluidics |
| Small Capillary | 0.5 – 1.5 | 0.020 – 0.059 | Instrumentation, sensors |
| Medium Capillary | 1.5 – 3.0 | 0.059 – 0.118 | Hydraulic, pneumatic systems |
| Large Capillary | 3.0 – 6.0 | 0.118 – 0.236 | Industrial, structural applications |
Wall Thickness Range
| Category | Wall Thickness (mm) | Wall Thickness (inches) | Pressure Rating |
|---|---|---|---|
| Ultra-Thin Wall | 0.025 – 0.05 | 0.001 – 0.002 | Low pressure (< 100 psi) |
| Thin Wall | 0.05 – 0.15 | 0.002 – 0.006 | Medium pressure (100-500 psi) |
| Standard Wall | 0.15 – 0.30 | 0.006 – 0.012 | High pressure (500-2000 psi) |
| Thick Wall | 0.30 – 0.50 | 0.012 – 0.020 | Very high pressure (> 2000 psi) |
Common Size Combinations
| OD (mm) | Wall (mm) | ID (mm) | Gauge (approx) |
|---|---|---|---|
| 0.30 | 0.05 | 0.20 | 32G |
| 0.40 | 0.05 | 0.30 | 30G |
| 0.50 | 0.10 | 0.30 | 28G |
| 0.60 | 0.10 | 0.40 | 27G |
| 0.70 | 0.10 | 0.50 | 26G |
| 0.80 | 0.15 | 0.50 | 25G |
| 0.90 | 0.15 | 0.60 | 24G |
| 1.00 | 0.20 | 0.60 | 23G |
| 1.20 | 0.20 | 0.80 | 22G |
| 1.50 | 0.25 | 1.00 | 21G |
| 2.00 | 0.30 | 1.40 | 19G |
| 3.00 | 0.30 | 2.40 | 17G |
| 4.00 | 0.50 | 3.00 | 15G |
| 6.00 | 0.50 | 5.00 | 13G |
Dimensional Tolerances
Outside Diameter Tolerance
| OD Range (mm) | Standard Tolerance | Precision Tolerance |
|---|---|---|
| 0.1 – 0.5 | ±0.02mm | ±0.005mm |
| 0.5 – 1.0 | ±0.02mm | ±0.01mm |
| 1.0 – 2.0 | ±0.03mm | ±0.01mm |
| 2.0 – 3.0 | ±0.05mm | ±0.02mm |
| 3.0 – 6.0 | ±0.05mm | ±0.03mm |
Wall Thickness Tolerance
| Wall Thickness (mm) | Standard Tolerance | Precision Tolerance |
|---|---|---|
| 0.025 – 0.05 | ±0.01mm | ±0.005mm |
| 0.05 – 0.10 | ±15% | ±10% |
| 0.10 – 0.20 | ±12% | ±10% |
| 0.20 – 0.50 | ±10% | ±8% |
Roundness Tolerance
| OD Range (mm) | Roundness Tolerance |
|---|---|
| 0.1 – 1.0 | ≤0.01mm |
| 1.0 – 3.0 | ≤0.03mm |
| 3.0 – 6.0 | ≤0.05mm |
Straightness Tolerance
| Length | Straightness Tolerance |
|---|---|
| Per meter | ≤0.5mm (standard) / ≤1.0mm (precision) |
| Total length | ≤2.0mm per 3m |
Material Grades
Austenitic Stainless Steels
| Grade | UNS | Key Properties | Common Applications |
|---|---|---|---|
| 304 | S30400 | General purpose, good corrosion resistance | Instrumentation, food, general industrial |
| 304L | S30403 | Low carbon, superior weldability | Welded assemblies, chemical processing |
| 316L | S31603 | Superior corrosion resistance, molybdenum | Marine, chemical, medical implants |
| 321 | S32100 | Titanium stabilized, high temperature | Exhaust, engine components |
| 347 | S34700 | Niobium stabilized, creep resistance | High temperature applications |
Ferritic and Martensitic Stainless Steels
| Grade | UNS | Key Properties | Common Applications |
|---|---|---|---|
| 409 | S40900 | Cost-effective, good oxidation resistance | Exhaust systems, catalytic converters |
| 430 | S43000 | Magnetic, formable | Magnetic sensor components |
| 420/420J2 | S42000 | High hardness, wear resistance | Surgical instruments, cutting tools |
Surface Finishes
Standard Surface Finishes
| Finish Type | Surface Roughness (Ra) | Appearance | Applications |
|---|---|---|---|
| Pickled | 0.8 – 1.5μm | Dull gray, matte | Industrial, general purpose |
| Bright Annealed | 0.4 – 0.8μm | Bright, reflective | Instrumentation, food, medical |
| Electropolished | 0.1 – 0.4μm | Ultra-bright, mirror | Medical, pharmaceutical, semiconductor |
| Polished | 0.2 – 0.5μm | Smooth, reflective | Decorative, food processing |
Length Options
| Format | Length Range | Coil Diameter | Applications |
|---|---|---|---|
| Coil | 1m – 30m | 100mm – 300mm | Flexible applications, long runs |
| Straight Length | 0.1m – 6m | N/A | Precision instruments, assemblies |
| Custom Cut | Per specification | N/A | Specific component requirements |
Applicable Standards
International Standards
| Standard | Title | Scope |
|---|---|---|
| ASTM A269/A269M | Seamless and Welded Austenitic Stainless Steel Tubing for General Service | General industrial, instrumentation |
| ASTM A213/A213M | Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes | High temperature, pressure applications |
| EN 10216-5 | Pressure equipment – Seamless steel tubes – Technical delivery conditions for stainless steel | European pressure equipment |
| JIS G3463 | Stainless steel tubes for automotive structural purposes | Automotive applications |
| ISO 1127 | Steel, stainless steel and titanium tubes – Outside diameters and nominal walls | Dimensional standards |
Medical Standards
| Standard | Title |
|---|---|
| ISO 9001:2016 | Medical device quality management |
| ISO 5832-1 | 316LVM stainless steel for surgical implants |
| ISO 7197 | Hypodermic needles and cannulae |
| ASTM F138 | 316LVM stainless steel for surgical implants |
How to Specify Your Capillary Tube
When ordering stainless steel capillary tubes, provide the following information:
- Material Grade: 304, 316L, 321, 420, etc.
- Outside Diameter (OD): mm or inches
- Wall Thickness: mm or inches
- Length: Coil or straight length, meters or feet
- Tolerance: Standard or precision
- Surface Finish: Pickled, bright annealed, electropolished
- Standard: ASTM, EN, JIS, or custom specification
- Quantity: Meters, feet, or number of pieces
- Certification: Material test report, EN 10204 3.1
Custom Specifications
We can manufacture capillary tubes to custom specifications including:
- Non-standard dimensions
- Special tolerances
- Custom surface treatments
- Special packaging requirements
- Custom length cutting
- Bending, flaring, and forming
Contact us with your specific requirements for a custom quote.
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