Capillary Tube Stainless Steel
We supply stainless steel capillary tube from 0.3 mm to 6 mm OD, in 304, 316L and 321. Walls run from 0.05 to 1.5 mm. Tube is supplied in coils, straight lengths or cut pieces.
OD tolerance down to ±0.01 mm
Bright annealed, half hard or full hard
Clean, dry bore; ends deburred on cut pieces
Most stock sizes 1.0–4.0 mm OD with 0.2–0.8 mm walls
Why Order SS Capillary Tube From MTS
01
Tolerance Measured, Not Assumed
OD and wall are measured on each lot with laser gauge or micrometer. The report ships with the goods.
02
Clean Inside
Bores are cleaned and dried after drawing. No oil or drawing residue for medical and analytical use.
03
Temper to Your Process
Annealed for bending and flaring. Hard for needles and probes that must stay straight.
04
Cut to Length With Clean Ends
We cut straight pieces from 5 mm to 2,000 mm long, deburred and free of burrs inside.
05
Processing Capacity and Stock
We process up to 100,000 tons a month and keep 3,000 tons of stainless pipe & tube in stock (out of 80,000 tons in total) in 60,000 m² of warehouse space in Wuxi. Our own cranes load each container for Shanghai, Qingdao or Tianjin.
Precision Where Size Is Measured in Hundredths
Capillary tube carries tiny flows of gas, fluid or signal. In that size, a 0.02 mm error in bore changes flow by a lot.
That is why precision stainless steel tubing goes into medical needles, sensors, chromatography lines, refrigeration controls and thermocouple sheaths. Stainless keeps the bore clean and corrosion free for years.
Capillary and Small Diameter Tubing Range
Medical Capillary Tube
304 and 316L tube for needles, cannulas and catheter parts. Hard or spring temper.
Instrument and Analytical Tube
316L small bore stainless steel tube for gas chromatography and sample lines. Bright, clean bore.
Stainless Steel Micro Tubing
OD below 1 mm for probes, nozzles and electronics. Also called miniature stainless steel tubing.
Small Diameter Stainless Steel Tubing
2mm to 6 mm OD for sensors, heating elements and refrigeration, in 50 m or 100 m coils or straight lengths. From 6 mm up, we supply seamless tube such as 6 × 1, 8 × 1 and 10 × 1.5 mm.
Bright Annealed Tubing
Bright annealed stainless steel tubing, soft and shiny, for bending, coiling and brazing. Our welded tube from 8 mm OD is bright annealed and tested length by length.
Thermocouple Sheath Tube
321 and 316 tube for temperature probes.
Specifications
| Item | Range |
|---|---|
| Grades | 304, 316L, 321; other grades on request |
| OD | 0.3 – 6.0 mm (most stock 1.0–4.0 mm) |
| Wall | 0.05 – 1.5 mm: thin 0.05–0.2, standard 0.2–0.8, heavy 0.8–1.5 |
| ID | From 0.1 mm |
| Small diameter tube | Seamless from 6 × 1 mm; welded and bright annealed from 8 × 0.8 mm |
| Length | Coils of 50 m or 100 m; straight stock 100, 300, 500 and 1,000 mm; cut to 5–2,000 mm; straight max 2 m |
| Temper | Annealed, bright annealed, 1/4 hard, 1/2 hard, full hard |
| Standards | ASTM A269, A632, ISO 9626 (needle tubing) |
How to Specify Stainless Steel Capillary Tube
Give Two of Three: OD, ID, Wall
Capillary tube is defined by OD, ID and wall. You only need two. Give OD and wall if the outside fits into something. Give ID and wall if flow matters most.
If you give all three, they must add up. We often receive drawings where OD minus two walls does not equal the ID. In that case, we ask which two to hold.
When you know only the bore, say so. A “1/8 ID” stainless steel tubing request is quoted by ID with your chosen wall.
Tolerance Costs Money
Standard tolerance is enough for most refrigeration and heating parts. Precision tolerance needs extra drawing passes and more inspection. It can double the price of small tube.
Order precision only on the dimension that matters. For a needle, that is usually OD. For a flow restrictor, it is ID.
Choose the Temper
Annealed tube is soft. It bends, coils and flares without cracking. Annealed stainless steel tubing is right for refrigeration lines and parts you form after delivery.
Bright annealed tube is annealed in a protective gas. It comes out shiny with no scale, so no pickling is needed. It is the usual choice for instrument and analytical lines.
Hard tube stays straight and resists bending. Use it for needles, probes and pins. Hard tube cannot be bent tightly.
Seamless or Welded and Redrawn
Seamless capillary tube starts from a seamless hollow and is drawn many times. Welded and redrawn tube starts from welded strip, then is drawn until the seam disappears in the structure.
For most uses, both perform the same. Some medical and high-pressure specs require seamless. Check your spec before ordering.
Grade Choice
304 suits most dry and mildly corrosive uses. 316L is preferred for medical, analytical and saline service. 321 holds up better in thermocouple and heating parts at high temperature.
Cleanliness and Ends
For analytical and medical tube, ask for cleaned and dried bores, capped ends and sealed bags. Drawing oil left inside will contaminate samples.
Cut ends should be square and free of burrs. Burrs inside a small bore block flow and trap dirt.
Frequently Asked Questions
What is the smallest ss capillary tube you can supply?
We supply OD down to 0.3 mm, with walls from 0.05 mm. Most stock sizes are 1.0–4.0 mm OD. Send your drawing with OD, ID and tolerance.
Can capillary tube be bent?
Yes, if it is annealed. Bend radius should be at least 2–3 times the OD for annealed tube. Hard tube may crack. Use a mandrel or bending tool to avoid flattening.
Is small stainless steel tubing sold in coils?
Yes. Capillary tube leaves the mill in coils, usually 50 m or 100 m long, which saves joints and freight. Straight pieces are cut from 5 mm to 2,000 mm, and stock straight lengths are 100, 300, 500 and 1,000 mm. Straight lengths over 2 m bend too easily, so they are rarely stocked.
What is the difference between capillary tube and instrument tube?
Capillary tube is usually below about 3 mm OD. Instrument tube is usually 1/8" to 1/2" OD, used with compression fittings. The line between them is not strict.
Do you supply medical grade capillary tube?
We supply 304 and 316L tube for medical device makers. Medical approval depends on your own validation. We provide material certificates and dimension reports.
How is capillary tube priced?
Small tube is priced per meter or per kilogram, depending on size. Tolerance, temper, cleaning and cut length affect cost. Send your drawing and annual quantity and we will quote within 2–4 working hours.
Request a Quote
We reply within 2–4 working hours with a price per ton, valid for 3 days.