Precision steel tube is cold drawn tube whose outside diameter, wall thickness and roundness are held tight enough to be used without further machining. We supply seamless precision tube to EN 10305-1 and DIN 2391, and welded cold drawn tube to EN 10305-2, cut to the length your production needs.
When precision tube instead of standard tube
A standard tube is judged on OD and wall. A precision tube is judged on the bore as well: in hydraulic cylinders, shock absorbers and fork tubes the inside surface is the running face of the seal. Three things decide whether it works:
- Dimensional tolerance. OD, wall and roundness have to match, otherwise the wall becomes uneven after machining.
- Surface. Cold drawn bores are smooth and free of scale, which is the starting point for honing or skiving.
- Straightness and wall eccentricity. A tube that moves in the chuck cannot be machined to size, and an eccentric wall gives an uneven chrome layer.
Steel grades
Precision tube is supplied in the grades defined by EN 10305-1 and DIN 2391: E235 and E355 to EN 10305-1, and St35, St45 and St52 to DIN 2391.
| Grade | Standard | Yield strength | Use |
|---|---|---|---|
| E235 | EN 10305-1 | ≥ 235 MPa | General precision tube, machinery, agricultural equipment |
| E355 | EN 10305-1 | ≥ 355 MPa | Higher-strength tube, hydraulic and machine building |
| St35 | DIN 2391 | ≥ 235 MPa | Drawings to DIN 2391 |
| St45 | DIN 2391 | ≥ 340 MPa | Machined tubes, medium load |
| St52 | DIN 2391 | ≥ 355 MPa | Higher-strength precision tube |
E235 is the standard grade for general precision tube. E355 is chosen where higher strength or a thinner wall is needed; St35, St45 and St52 cover drawings to DIN 2391. Other grades are checked against the drawing.
Condition and tolerances
Cold drawn tube is supplied annealed (BK or GBK), deburred, oiled and cut to length. Dimensional, form and wall tolerances follow EN 10305-1 or DIN 2391; the tolerance class is agreed at quotation because it depends on diameter, wall and length.
Standard sizes
The sizes below are produced regularly. Other sizes are made to drawing — send OD, wall and length and we will confirm the nearest available tube.
| Size | OD | Wall | ID | Weight |
|---|---|---|---|---|
| 60 × 10 mm | 60 mm | 10 mm | 40 mm | 12.33 kg/m |
| 22 × 4 mm | 22 mm | 4 mm | 14 mm | 1.78 kg/m |
| 18 × 1 mm | 18 mm | 1 mm | 16 mm | 0.42 kg/m |
Applications
- Hydraulic and pneumatic cylinders
- Shock absorbers and suspension struts
- Motorcycle fork tubes
- Steering and axle components
- Bushings, rollers and machined parts
Quality control
Every batch is checked before packing: mill certificate matched to the heat number, OD and ID at both ends and mid-length, wall at four points, bore surface inspection and length check. Inspection records are kept against the order and can be issued with the shipping documents. 3.1 certificates to EN 10204 are available on request.
What to send with an enquiry
- Outside diameter and wall, or the drawing
- Length per piece and total quantity
- Steel grade, or the working pressure if the grade is open
- Condition: as drawn or annealed
- End finish: plain, deburred, threaded
- Surface: oiled, painted, zinc plated
FAQ
What is the difference between precision tube and seamless tube?
Seamless describes how the tube is made; precision describes the tolerance. A seamless tube can be loosely toleranced — cold drawing to a tighter tolerance is what makes it a precision tube.
Which grades do you supply?
E235, E355, St35, St45 and St52. Other grades are checked against the drawing.
What tolerances can you hold?
The tolerance class is set per size because it depends on diameter, wall and length. Tell us the required tolerance and we will confirm feasibility.
Do you supply cut lengths?
Yes. Tubes are cut to length, deburred and oiled before packing.
How fast do you quote?
With size, quantity and grade, usually within one working day.
Related pages: Seamless steel tube · Hydraulic cylinder tube · 60 × 10 mm · 22 × 4 mm · 18 × 1 mm