High precision cold drawn DOM welded tubes are ERW carbon steel mechanical tubes processed by cold drawing over a mandrel to improve OD/ID accuracy, wall uniformity, concentricity, surface finish, and mechanical stability. They are suitable when ordinary ERW tubing is not precise enough for machining, press-fitting, bearing support, or controlled assembly clearance. For international purchasing, the recommended baseline is ASTM A513/A513M Type 5 for DOM mechanical tubing or EN 10305-2 for welded cold drawn precision tubes.

• Controlled OD, ID, and wall uniformity
  Diameter tolerance can be controlled from ±0.08 mm on smaller precision sizes up to ±0.80 mm on larger EN preferred sizes. Wall thickness tolerance is normally ±7.5% or ±0.10 mm, whichever is greater. When both OD and ID are specified, eccentricity control can be applied to improve concentricity.
• Stable straightness for machining and assembly
  For tubes above 15 mm OD and longer than 1000 mm, straightness can be controlled to 0.0015L for yield strength up to 500 MPa, with a maximum deviation of 3 mm over any 1 m length unless tighter straightness is agreed.
• Defined surface roughness
  The OD and ID surfaces are smooth after cold drawing, with an EN 10305-2 reference roughness of Ra ≤ 4 µm. Lower roughness values can be specified when the tube is used for sliding, telescopic, sealing, or precision-fit components.
• Selectable mechanical strength level
  In normalized condition, EN 10305-2 grades cover tensile strength from 270-410 MPa for E155 up to 490-630 MPa for E355. In stress relieved condition, E355 can reach minimum Rm 590 MPa, ReH 435 MPa, and elongation 10%.
• Weld seam quality verification
  For critical use, NDT can be specified for longitudinal imperfections or leak-tightness. Eddy current, flux leakage, or ultrasonic methods can be used depending on the selected standard and acceptance level.
• Practical end preparation
  Tubes are supplied with square-cut ends free from harmful burrs. Deburring, chamfering, or special end finishing can be specified for automated assembly or machining lines.

Automotive shock absorber cylinder tube -- used where the tube must provide controlled ID, stable straightness, good surface condition, and predictable mechanical performance for piston movement and assembly reliability.