ITMC Blueprint Reading 2 — Questions and Answers
Question 1: On a mechanical drawing, what does a hidden line (dashed line) represent?
- A surface that is visible from the current view
- An edge or feature not visible from the current viewing angle (Correct answer)
- A centerline for symmetrical features
- A cutting plane for a section view
Correct answer: An edge or feature not visible from the current viewing angle
Hidden lines (dashed) show edges or features that exist behind visible surfaces in the current view.
Question 2: What is the purpose of a revision block on an engineering drawing?
- To list all materials used in the assembly
- To record changes made to the drawing after its initial release (Correct answer)
- To specify the drawing scale and units
- To identify the drafting software version used
Correct answer: To record changes made to the drawing after its initial release
The revision block documents changes, dates, and descriptions of modifications made to a drawing after original issue.
Question 3: A first-angle projection differs from third-angle projection primarily in that:
- It uses different line weights for features
- The view is placed on the opposite side from where the observer looks (Correct answer)
- It only applies to circular parts
- Dimensions are placed inside the part outline
Correct answer: The view is placed on the opposite side from where the observer looks
In first-angle projection (common in Europe), the view is projected onto the plane beyond the object, opposite to the observer's side.
Question 4: On a blueprint, the symbol GD&T uses for flatness is:
- A circle with a crosshair
- Two parallel horizontal lines (Correct answer)
- A triangle pointing upward
- A rectangle with diagonal lines
Correct answer: Two parallel horizontal lines
The GD&T flatness symbol is two parallel horizontal lines, indicating that a surface must lie within two parallel planes.
Question 5: What does 'MAX' written next to a dimension on a blueprint indicate?
- The dimension is a reference only
- The feature must not exceed that value (Correct answer)
- The feature must equal that value exactly
- The dimension applies to both ends
Correct answer: The feature must not exceed that value
'MAX' indicates an upper limit — the manufactured feature must be at or below that value.
Question 6: In a piping and instrumentation diagram (P&ID), a dashed line connecting two instrument symbols typically indicates:
- A mechanical linkage between components
- An electrical or signal connection (Correct answer)
- A pneumatic tubing run
- A future installation path
Correct answer: An electrical or signal connection
On P&IDs, dashed lines represent electrical or signal connections between instruments or controllers.
Question 7: A scale of 1:2 on a drawing means:
- The drawing is twice the actual size of the object
- The object is drawn at half its actual size (Correct answer)
- The object is drawn at twice its actual size
- One drawing unit equals two feet
Correct answer: The object is drawn at half its actual size
A 1:2 scale means one unit on the drawing equals two units in reality, so the drawing is half the actual size.
ITMC Blueprint Reading 2
On a mechanical drawing, what does a hidden line (dashed line) represent?