The Drawing That Looked Complete

Ranking by consequence - what would actually make a bad part.

1. Chamfer dimensioned 1 × 22.5°. A drawing is always dimensioned to true size, whatever the scale. The trainee scaled the drawing at 1:2 and then halved the dimension as well; he also halved the angle, which is never scaled. A machinist following this sheet cuts a 1 mm chamfer at 22.5° - not the specified 2 × 45°. Both the size and the form are wrong, and the part is scrap or needs rework.
2. Projection mismatch. A plan view placed above the front view is third-angle practice, but the title block says first angle. A fabricator trained on first angle will read the plan as the underside, invert the bracket and machine the bore 45 mm below the base instead of above. The projection symbol is missing, so there is no tie-breaker. This is the error most likely to produce a totally wrong part rather than a slightly wrong one.
3. Hole spacing from a finished edge instead of the bore axis. The bracket works only if the holes and the bore stay in a fixed relationship. Dimensioning from a machined edge builds two tolerance stacks into one functional relationship; dimensioning from the bore axis (the datum) makes the hole positions independent of the edge. On a bracket this is a fit-up failure at assembly, not a scrap at the machine.
4. 120 mm dimensioned twice. Two dimensions for one feature give an inspector no rule for which governs and invite a conflict if one is altered. It is a drafting offence, but a fabricator usually spots it.
5. Missing hidden lines for the bore in the plan view. Poor practice, but the fabricator still sees the bore in the front view, so it rarely causes a bad part.
6. No surface finish symbol, no general tolerance note, no projection symbol. The sheet is not self-contained. It cannot be quoted or inspected without a conversation, which is the definition of an incomplete drawing.

The line to give him. 'The shape being clear is not the test. The test is whether a machinist you have never met can make the part correctly from this sheet alone.'

Marks.

• Views: 5/10. The geometry is right and the views are consistently drawn - but a consistent third-angle set under a first-angle title block is not a correct view layout, it is a wrong instruction. Deduct 3 for the projection error, 1 for the missing hidden lines in the plan view, 1 for the missing projection symbol. Do not deduct for neatness; it is not in the rubric.
• Dimensioning: 2/10. Deduct 4 for the chamfer (wrong size and wrong angle - the highest-value single error), 2 for dimensioning from the edge instead of the datum, 1 for the duplicated 120 mm, 1 for the missing surface finish and general tolerance note. The Ø40 H7 and the 45 mm height dimension are correctly given, which is why it is not zero.

Feedback as returned.

Geometry and line work are good; your problem is drafting convention, not drawing skill.

1. You drew a third-angle layout under a first-angle title block. Choose one, state it, and add the symbol.
2. A dimension is always the true size. At 1:2 the drawing is half size, the dimension is not. Angles never scale - 2 × 45° stays 2 × 45°.
3. Dimension the holes from the bore axis, not from the machined edge. The bore is the datum; the edge is a convenience.
4. Two dimensions for 120 mm: delete one.
5. No finish, no general tolerance, no projection symbol. The sheet is not inspectable. Resubmit the dimension block only, tomorrow, for the dimensioning marks to be reviewed.

Judgement on the resubmission. Offering the resubmission of the dimension block only is deliberate: it targets the assessed weakness without giving him a free redo of the whole sheet, and it keeps the mark defensible if he does not take it up.

The demonstration: one object, two sheets, one symbol.

Take a simple asymmetric object - a stepped block with a hole through the side, nothing more. Draw its front view on the board. Then draw the plan view below it, say 'first angle', and point to the projection symbol. Rub out the plan, draw it above the front view, say 'third angle', and point to the symbol again. Same object, same views, opposite instruction.

Then the test question, out loud, no notes: 'The plan is above the front view. Which angle, and where will the machinist think the hole is?' Take answers from four or five trainees, not the first hand up.

Why this and not a lecture. The trainee's error is not ignorance of the rule; he drew consistently, which means he has a system - it is just not the one his title block declares. Twenty minutes of theory will not shift an established habit. A side-by-side flip does, because it shows that the layout is the instruction and the symbol is what makes it unambiguous.

Follow-through, two minutes. Give the rule as a single sentence they write in the drawing file: top view below = first angle, top view above = third angle, and the symbol always decides.

How you know it landed. In the assessment, count how many sheets carry the projection symbol and how many have view placement consistent with the title block. Target 25 of 30 on both. If the symbols appear but placement is still mixed, the batch has learned the ritual and not the rule - reteach before the next drawing assignment, and record it in the section log.