Short answer: A good drawing review checks, in this order, that the drawing is the right document (title block, revision, standard), complete (every feature defined once, no missing views or dimensions), manufacturable and inspectable (tolerances, GD&T, datums, finish), and consistent with the model, the BOM and the previous revision. Use a written checklist so every reviewer covers the same ground. Give each comment a location and a requested action.
The checklist
1. Title block and document control
- Correct part number, description and revision letter.
- Material and finish are stated, or referenced to a spec.
- The governing standard is named (for example ASME Y14.5-2018 or ISO GPS), along with units and projection method (first or third angle).
- General tolerance block or general tolerance standard (for example ISO 2768) applies only where intended.
- Scale, sheet count, and drawn, checked and approved fields.
2. Views and representation
- Enough views to define every feature with no ambiguity. Use section views where internal features matter.
- Hidden lines only where they add clarity.
- Detail views at a readable scale, with labels matching their callouts.
- Thread callouts follow the standard (for example ISO 965 or ASME B1.1 designations).
3. Dimensions
- Every feature is fully defined, with no double dimensioning and no unnecessary reference dimensions.
- Dimensions come from functional datums, not from convenient edges.
- No dimensions to hidden lines where avoidable. No chained dimensions where accumulation matters.
- Units and decimal places are consistent with the tolerance convention.
4. Tolerances and GD&T
- A datum reference frame exists and reflects how the part mounts and functions.
- Feature control frames are complete: symbol, ⌀ where needed, value, modifiers and datums.
- Basic dimensions are boxed wherever position or profile is used.
- Fits are stated with ISO 286 classes or explicit limits, not "slip fit."
- Surface finish is called out on functional surfaces (sealing faces, bearing bores, sliding surfaces).
5. Notes
- Notes are numbered, specific and not contradictory.
- Deburr, edge break, cleaning, marking and packaging are specified where they matter.
- For cleanroom or UHP parts: cleaning spec, handling, and bagging requirements.
- Welding: weld symbols per AWS A2.4 or ISO 2553, a weld spec reference and inspection requirements.
6. Assembly drawings
- Balloons match BOM item numbers, and each item appears once.
- BOM quantities match the model.
- Hardware has torque or installation notes where needed.
- Critical interfaces are dimensioned for inspection at the assembly level.
7. Revision control
- The revision table describes every change, and changes are marked on the sheet (clouds or flags, per company practice).
- Only intended changes happened. Compare against the previous released revision.
Worked example
A reviewer checks Rev C of a bracket.
1. Title block: the revision letter is C, but the revision table only lists A and B. Comment: "Add Rev C entry describing changes."
2. Views: a slot appears only in the top view, and its depth isn't shown. Comment: "Add section A-A through slot, dimension depth."
3. Dimensions: the overall length is dimensioned both overall and as a chain of three segments. Comment: "Remove one segment or mark as reference."
4. GD&T: a four-hole pattern has a position callout, but datum B isn't identified anywhere on the sheet. Comment: "Add datum feature symbol B."
5. Revision compare: overlaying Rev B and Rev C shows a hole size changed from ⌀6.6 to ⌀6.4. The revision table doesn't mention it. Comment: "Confirm intended. If so, describe it in the revision table."
Point 5 is the most common real-world miss: a change nobody declared. A visual diff of the two revisions catches it quickly. You can use your CAD tool's compare function or a free tool such as MST's DrawingDiff, which highlights what changed between two drawing PDFs.
Common mistakes
- Reviewing only what changed, as declared in the revision table, instead of comparing the full sheet against the previous revision.
- Comments without a location or action, such as "dimensions unclear."
- Accepting general tolerances on functional features.
- Leaving out the standard edition. Y14.5-2009 and Y14.5-2018 differ in some rules.
- Treating the model as the authority when the drawing is the contract document, or the other way around, without stating which one governs.
- Missing inspection feasibility. A feature that can't be measured as specified will be "interpreted" on the shop floor.
Writing useful review comments
A good comment has a location (sheet, zone, view), what is wrong, and the requested action. "Sheet 2 zone C4, section B-B: thread depth missing. Add depth per standard" can be acted on. "Check threads" can't. Track comments in a list with a status (open, accepted, rejected with reason) so the next revision can be checked against it.
FAQ
Should I review the model or the drawing?
Both, but the release document defines what governs. If it's model-based definition, review the annotated model to the same checklist.
How long should a review take?
It depends on complexity. A checklist keeps it consistent, and splitting into passes (document, geometry, tolerances, notes) avoids fatigue.
Who should review?
A peer designer for geometry and function, plus manufacturing and quality for producibility and inspection, on critical parts.
What about legacy drawings without GD&T?
Review them against the standard they were made to. Add GD&T only through a formal revision.