Specialist tubing

Stainless Steel Capillary Tubes

Request capillary tube pricing by grade, outside diameter, bore, wall tolerance and cut length.

Technical reference

Specifications and ordering data

Specification

Field	Order reference
Standard	A632 small-diameter austenitic tubing where applicable, or the approved drawing
Product or route	Small-bore straight tube or continuous coil
Critical dimensions and fit	Give bore tolerance and prioritise OD or ID if both are tightly controlled
Supply enquiry	Confirm sizes, lengths, route, documentation and lead time for your order

Dimensions and weight

Illustrative drawing sizes. The bore and mass are calculated from the nominal dimensions. Use the project tolerance and confirm the size and route in the quote.

Tube OD (mm)	Wall (mm)	Nominal bore (mm)	Estimated kg/m at 8,000 kg/m³
1.6	0.3	1.00	0.01
2	0.5	1.00	0.02
3	0.5	2.00	0.03

Service and pressure basis

Use the approved design code and service conditions. The applicable rating depends on material, temperature, minimum effective wall, joint details and the limits of the connected assembly. A schedule or a hydrostatic test result alone cannot establish an operating pressure.

Reference ASME process piping code B31.3

Chemical composition

The grade on the purchase line controls chemistry. Specify the grade with the finished product standard or drawing.

Check	What to match
Grade and specification	TP or UNS on the quotation and material report
Heat analysis	Full limits and any stabilising or alloy additions under the ordered edition

Reference ASTM steel standards

Mechanical properties

Use the ordered grade, delivery condition and product standard to review the actual tensile, yield, elongation or hardness results required by the order.

Check	What to verify
Condition	Heat treatment or cold-work condition stated for the offered form
Acceptance	Project-specified dimensions and relevant test records

Reference ASTM steel standards

Testing and certificates

Check end burrs, bore gauging, cleanliness and lot identification.

When	What to check
Before ordering	Document the required test method, edition and any witness points
At delivery	Match the material report and heat or lot identification to the shipment

Application and product comparison

Instrumentation tube is typically selected to match the exact fitting OD.

For the enquiry, give bore tolerance and prioritise OD or ID if both are tightly controlled.

Example request for quotation

A632 small-diameter austenitic tubing where applicable, or the approved drawing · 1.6 × 0.3 mm. Add quantity, lengths, delivery city and the required reports.

Request a quote

Ordering guidance

Specify which small dimension controls performance

Give actual OD, bore or ID and the required tolerance. If wall thickness is used instead of bore, state it clearly. When all three are listed, identify the dimensions that govern acceptance if tolerances overlap.

For a repeat order, include cut length, end condition and any cleanliness or finish requirements. If the tube must mate with a fitting, include the fitting or assembly drawing rather than relying on the word capillary.

Check pricing and availability →

Illustration: Small-bore stainless tubes and a continuous coil

Buyer’s guide

Capillary tubing for controlled bore and small connections

Specify the bore as well as the OD

Two capillaries can share the same outside diameter and have different bore sizes. If flow or response time matters, give the inside diameter and its tolerance along with the OD or wall specified by the drawing. If the order defines both OD and ID, state which limits govern when tolerances are evaluated.

Protect small ends during preparation

Short cut pieces can be sensitive to burrs, flattened ends or contamination. Specify how cut ends are to be deburred, cleaned and protected. If the tube must accept a wire, pin or fitting, give the clearance or approved gauging requirement. For coils, give the required continuous length and any restrictions on joins.

Tie inspection to the application

For sampling, analytical instruments or metering, send the equipment drawing and any cleanliness, leak or dimensional tests it calls for. Specify units clearly on mixed inch and metric orders. Small dimensional differences may be difficult to see at receiving, so agree how the supplier will identify each size and pack separate lots.

Example enquiry

For a metering line, give actual OD, the critical bore and tolerance, clean-cut ends and the number of pieces or unbroken coil length. Add the approved material and inspection requirements from the instrument drawing.

Can the supplier infer flow capacity from the tube OD?

The outside diameter alone leaves the bore unknown. Give the bore and use the application’s approved flow calculations and tolerances.

Technical references ASTM steel standards directory

Prepare your enquiry

What to put on the purchase list

Item	What to send
Product details	OD · ID or wall · controlling tolerance · cut length · end condition
Delivery	Quantity with units, delivery city and required date if known
Acceptance	Required certificates and inspection scope; attach the drawing revision where applicable

Is a “thin-wall tube” automatically a capillary tube?

No. State the actual dimensions and tolerances; those define what can be compared and quoted.

Technical reference: ASTM steel standards catalogue

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Project enquiries

Request pricing and availability

Send your dimensions, quantities and delivery city. Include any inspection or material certificate requirements so they can be quoted against the same line items.

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