Tube stockists hold a huge variety of standard tube sizes but could not possibly hold every possible size as some applications call for tolerances of less than 0,02mm on the bore and outside diameter resulting in a lack of availability. The surface finish requirements also vary greatly from simply rough pipe to house or protect another component or cabling all the way through to highly polished bore finishes for hydraulic cylinders or mating part matching.
As a result, customers can often struggle to procure the exact specification they need.
Re-machining standard, stock tubes can often be as expensive as machining the tube to specification from solid bar material. This is for several reasons, straightness can sometimes be an issue and it’s extremely difficult to correct bend without sufficient material to remove and in other cases, it could be that tooling is not currently developed to machine the entire length of the bore to increase the size or improve the surface finish.