AIT Technical Drawing 5 — Questions and Answers
Question 1: What is the purpose of a 'break' symbol on a long uniform part in a technical drawing?
- To indicate where the part is intentionally cut during manufacturing
- To shorten the drawing representation without changing the stated length dimension (Correct answer)
- To show a stress concentration or fracture location
- To indicate a change in cross-section along the length
Correct answer: To shorten the drawing representation without changing the stated length dimension
Break lines allow a long, uniform object to be drawn at a larger, clearer scale while the true overall length is still specified in the dimension.
Question 2: In the Unified thread system, what does the designation 'UNF' indicate compared to 'UNC'?
- UNF threads are used for fluid fittings; UNC is for structural connections
- UNF has more threads per inch (fine pitch); UNC has fewer threads per inch (coarse pitch) (Correct answer)
- UNF is an internal thread; UNC is an external thread
- UNF requires a tap; UNC is a self-tapping thread
Correct answer: UNF has more threads per inch (fine pitch); UNC has fewer threads per inch (coarse pitch)
Unified National Fine (UNF) threads have a smaller pitch and more threads per inch than Unified National Coarse (UNC), providing greater holding strength in thin materials.
Question 3: A 'spotface' operation is called out on a drawing when:
- A decorative surface finish is required on a cast surface
- A small flat bearing area must be machined around a hole on a rough or curved surface (Correct answer)
- A tapered recess is needed to accept a flat-head screw
- The hole depth must be precisely controlled
Correct answer: A small flat bearing area must be machined around a hole on a rough or curved surface
Spotfacing machines a shallow, flat circular area around a hole so a bolt head or washer seats squarely on an otherwise rough or angled surface.
Question 4: What does the abbreviation 'TYP' mean when placed next to a dimension on a drawing?
- The dimension is approximate and for reference only
- The same dimension applies to all identical features unless noted otherwise (Correct answer)
- The tolerance is tighter than the general title-block tolerance
- The feature must be machined using a template
Correct answer: The same dimension applies to all identical features unless noted otherwise
'TYP' (typical) indicates that the dimension or note applies to every similar feature on the drawing without having to dimension each one individually.
Question 5: Which view is added to a multiview drawing when a surface is not parallel to any principal projection plane?
- An isometric view
- An auxiliary view (Correct answer)
- A perspective view
- A revolved section view
Correct answer: An auxiliary view
An auxiliary view is projected perpendicular to the inclined surface so its true shape and size are shown without distortion.
Question 6: When a drawing callout reads 'Ø.375 ±.005 THRU', what does 'THRU' specify?
- The hole tolerance applies through the full thickness of the material
- The hole goes completely through the part from one side to the other (Correct answer)
- The thread runs through the entire length of the hole
- The dimension is verified by a go/no-go gauge through the part
Correct answer: The hole goes completely through the part from one side to the other
'THRU' (or 'THROUGH') indicates the hole passes entirely through the part, eliminating any ambiguity about depth.
Question 7: In a surface finish callout, what does the Ra value represent?
- The maximum peak height allowed on the surface
- The arithmetic average roughness of the surface measured from the mean line (Correct answer)
- The minimum acceptable surface hardness after machining
- The required number of machining passes to achieve the finish
Correct answer: The arithmetic average roughness of the surface measured from the mean line
Ra is the arithmetic mean of the absolute deviations of the surface profile from the mean line, expressed in microinches or micrometers.
AIT Technical Drawing 5
What is the purpose of a 'break' symbol on a long uniform part in a technical drawing?