A hydraulic cylinder tube is the precision steel tube used to make the cylinder barrel. The bore becomes the running surface of the piston seal, so inside diameter, tolerance and roughness decide whether the cylinder stays tight. We supply seamless cylinder tube in 27SiMn, 16Mn, 45# and 20#, cold drawn or honed, with bore sizes from 15 to 100 mm.
What matters in a cylinder tube
- Bore and tolerance. H8 or H9 is usual. A 0.05 mm deviation changes the seal clearance.
- Roughness. Honed bores sit at Ra 0.2–0.4 µm. Longitudinal drawing marks wear the seal even when the diameter is correct.
- Wall and eccentricity. The wall carries the pressure; an uneven wall gives an uneven chrome layer after plating.
- Straightness. A bent tube cannot be held in the chuck and machined to size.
Steel grades
| Grade | Yield strength | Use |
|---|---|---|
| 27SiMn | ≥ 835 MPa | High-pressure cylinders, construction, mining |
| 16Mn (E355) | ≥ 345 MPa | High pressure with medium wall |
| 45# (AISI 1045) | ≥ 355 MPa | Barrels machined after welding |
| 20# (AISI 1020) | ≥ 245 MPa | General cylinders, agricultural equipment |
Supply condition
Cold drawn tube is supplied with grinding allowance, typically 0.3–0.5 mm on the bore. Honed or SRB tube is supplied ready to assemble at Ra 0.2–0.4 µm. Both routes are available: honing for corrected or small batches, SRB for production runs.
Standards
Dimensions and tolerances follow EN 10305-4 or DIN 2391. The tolerance class is agreed per size because it depends on diameter, wall and length.
Sizes
Bore from 15 to 100 mm, wall to drawing, cut to length. Send the ID, OD or wall, and the length, and we will confirm the nearest available size.
Quality control
We measure the bore at both ends and mid-length in two directions, wall at four points, roughness at three positions, plus straightness and length. Records are kept against the order and 3.1 certificates are available.
FAQ
What is the difference between cold drawn and honed?
Cold drawn is the starting condition with grinding allowance. Honed is the finished bore with a defined roughness.
Which grade for high pressure?
27SiMn is the usual choice because the high yield strength allows a thinner wall. 16Mn covers many medium-pressure applications.
Do you supply SRB?
Yes. SRB suits series production; honing suits corrected or smaller batches.
For the product specification and quotation, see the Hydraulic Cylinder Tube product page.