Final surface resulting in the cold drawn tubes is caused by the condition of the mother tube, because during its hot drilling the tube gains spiral shape (pic A) which is maintained even if reduced, after rolling and drawing (pic B).
Traditional finishing processes of honing and rolling follow this spiral trend, obtaining the requested tolerance and without modifying the spiral shape which is in direct opposition with the principal of concentricity for the specific group: PISTON/TUBE.
Picture c, is demonstrating the extreme straightness of the inside finish, known as “ALTA finish”. The machining of a tube with a reduced inside stock allowance, is generating raw material spots (in the picture the darker spots) those areas are outside of the maximum tolerated straightness, due to the spiral shape of the tube.
To avoid these problems ALTA sources tubes with a higher stock allowance, over and above the norm (up to 3 mm in diameter) removing the necessary material, allowing a better straightness, roundness and surface cleaning finish, against the traditional systems
|Dimensional Range||From O.D. 42 mm to O.D. 305 mm | wall thickness from 5 mm to 25 mm|
metric and imperial size range available
|Lenght||till 12 m|
fix or multiple length on demand
|Type||Ready for skiving|
skived and roller burnished
|Inside Tolerances||H8 | H9 | H10 | H11|
|Steel Grade||E355 | E410|
others on request
|Test Certificate||EN 10204:2004/3.1|