No drawing is checked point by point, because not every figure matters equally. A dimension is critical when it decides whether the part fits, seals, aligns or clears something else. Everything downstream of that is produced to the nominal figure and checked for consistency rather than for precision.
On a fabricated part the critical set is usually short: mounting hole centres, flange face angle, the position and direction of a pipe end, the bore at a sealing face, and any clearance the part needs from a component beside it. Once those are identified, the rest of the inspection falls into place.
Every dimension needs a reference. Measuring a part from a convenient edge rather than from a defined datum produces figures that cannot be compared with the drawing, even when the part is correct. Datums exist so that two people measuring the same part describe it the same way.
On a welded assembly, that often means using a machined face, a bore or a pair of mounting points as the reference and measuring everything else relative to them. A part that is right in itself but measured from the wrong reference generates a discrepancy that costs time to resolve.
Flange faces are checked for flatness and for angle, because a face that is not square will not seal no matter how well the bolt holes line up. Bore sizes are checked at the sealing face and along the run, since a bore that closes slightly near a weld will pass a gauge at one end and not the other.
Hole centres and their span are measured as a set, along with the diameter and the direction of any pipe end. On a part that connects at two points, the distance between those points and the relative angle between them usually decide whether the part can be bolted up without forcing anything.
A jig or fixture is often the fastest inspection tool available, because it holds the part in the same positions used to build it. If the part drops onto the fixture without effort, the key geometry is within the tolerance the fixture was built to.
The limit is that a jig only checks what the jig was made to check. A fixture can confirm hole positions while saying nothing about wall thickness, bore condition or finish. Gauges and hand instruments cover what the fixture does not, and the two are normally used together.
A measurement written down against the drawing figure can be reviewed, compared and acted upon. A note that says a part fits is not a result, because it does not say where it was measured or against what. The value of the record is that a second person can reach the same conclusion without repeating the whole exercise.
Photographs belong with that record, showing the measured features and any area that needed attention. When a batch runs later, the earlier record is what tells you whether anything has shifted.
Being out of tolerance is not always a scrapped part. The first question is whether the measurement sits inside the range the part actually needs, which is not always the same as the range written down. The second is which side of the tolerance it falls on, because being oversized is often recoverable while being undersized may not be.
The judgement is always made against the drawing, since that document is the shared definition of the part. On custom work the drawing is created early and used throughout, either from a customer's own dimensions, material and special requirements, or from an engineer gauging a sample and producing it. How that path runs is set out on the custom work page, and it applies to assemblies such as the titanium fab components range just as it does to a single fabricated pipe.
