AIT Technical Drawing 3 — Questions and Answers
Question 1: What is the correct reading direction for a unilateral tolerance such as +0.005 / -0.000?
- The dimension may only vary in the negative direction
- The dimension may only vary in the positive direction (Correct answer)
- The dimension can vary equally in both directions
- The tolerance applies only to the nominal value
Correct answer: The dimension may only vary in the positive direction
A unilateral tolerance of +0.005/-0.000 means the actual size may be up to 0.005 larger than nominal but no smaller.
Question 2: On a welding symbol, where is the reference line drawn?
- Vertically, connecting the arrow to the tail
- Horizontally, with the arrow on one end and the tail on the other (Correct answer)
- As a dashed circle around the weld location
- Diagonally at 45 degrees from the joint
Correct answer: Horizontally, with the arrow on one end and the tail on the other
The welding symbol reference line is always horizontal; the arrow points to the joint and the tail holds supplementary information.
Question 3: What does an 'R' prefix before a dimension value indicate?
- The dimension is a reference (non-mandatory)
- The feature is a radius (Correct answer)
- The surface requires a reamed finish
- The dimension applies to a right-hand thread
Correct answer: The feature is a radius
The prefix 'R' designates a radius dimension, measured from the center of the arc to its circumference.
Question 4: In a thread callout '1/2-13 UNC-2A', what does '2A' specify?
- The thread is 2 inches long with an A-grade finish
- The thread class of fit — external thread with moderate allowance (Correct answer)
- The second pass in a two-pass threading operation
- The thread starts at position A on a 2-start helix
Correct answer: The thread class of fit — external thread with moderate allowance
In the Unified thread system, class 2A denotes an external thread with a standard allowance suitable for most general applications.
Question 5: What information is typically found in the title block of a technical drawing?
- Bill of materials and part quantities only
- Part name, drawing number, scale, material, tolerances, and approvals (Correct answer)
- Only the drafter's name and date
- The assembly sequence and torque specifications
Correct answer: Part name, drawing number, scale, material, tolerances, and approvals
The title block consolidates essential administrative and technical information needed to identify and use the drawing correctly.
Question 6: A phantom line (long dash, two short dashes) is commonly used to show:
- The cutting plane for a section view
- Alternate positions of a moving part or adjacent parts (Correct answer)
- Hidden interior features of a solid
- Extension lines for chain dimensioning
Correct answer: Alternate positions of a moving part or adjacent parts
Phantom lines depict alternate positions, repeated detail, or the outline of adjacent parts without implying they are part of the main object.
Question 7: When dimensioning a drawing using the baseline (datum) method, all dimensions originate from:
- The geometric center of the part
- A single common reference surface or point (Correct answer)
- The largest feature on the part
- The previous dimension in the chain
Correct answer: A single common reference surface or point
Baseline dimensioning measures every feature from one fixed datum, preventing the accumulation of tolerances found in chain dimensioning.
AIT Technical Drawing 3
What is the correct reading direction for a unilateral tolerance such as +0.005 / -0.000?