Seamless tubes are characterized by high mechanical properties and could be made by special steels upon request.
Dimensional tolerances, surface quality and eccentricity are realized and checked according to the norm UNI EN ISO 10305-1.
A.L.T.A. Spa might supply a very wide range of sizes on request.

By the tube piercing, the mother pipe gets a spiral shape (picture a) which is not a lot modified during the hot rolling and cold drawing process (picture b).

The traditional finishing system called honing and/or roll burnishing, follows the spiral and, even if within the required tolerance, does not modify the defect of spiral shape of the tube against the good function of the cylinder components which requires the perfect coaxiality between rod-piston-cylinder body. The evidence of ALTA finishing system extreme straightness comes out from the picture (c). The machining of a cold drawn tube with a small inside stock allowance shows some raw material stains (the dark spots into the tube of picture c) where the A.L.T.A. Spa machining system was not efficient enough because those raw stain areas were outside the max. allowed straightness tolerance.

To avoid this problem, A.L.T.A. Spa uses tubes with greater inside stock allowance than the norms expects (up to 3 mm on diam.) to grant always perfect straightness, roundness and surface cleaning.


a   b

c

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