There is a lot of confusion about how round a mechanical tube really is when received from the mill or even after grinding or honing operations.
Tolerance and Ovality are two completely different topics. When discussing DOM or SSID tubing, the limits are defined in ASTM specification A513 and in the sections concerning types 5 and 6, respectively.
Here’s the confusing part of it all. The spec states that ovality shall be within tolerances except when the wall thickness is less than 3% of the outside diameter. While the mean outside diameter is within tolerance there could exist additional ovality of 0.010″ (0.25mm) up to 2″, all the way to 0.065″ (1.65mm) at diameters over 12″ O.D.
Seamless is a completely different product and the chart in ASTM specification A519 is really intense with numerous exceptions and foot notes. The tolerances and ovality mostly exceed those listed in A513.
The best path to follow is to let your sales representative know the tolerance you require and how you plan on measuring it – with a 2 point or 3 point micrometer for instance. We will gladly check our stock and report the findings before entering the order thus reducing the possibility of a claim or reject.
Hope this helps!