OIT Blueprint Reading and Technical Drawing 2 — Questions and Answers
Question 1: On a blueprint dimension, what does a tolerance notation of '25.00 ± 0.05' indicate?
- The feature must be exactly 25.00 units
- The feature may range from 24.95 to 25.05 units (Correct answer)
- The feature must be at least 25.00 units
- The tolerance applies only to the surface finish
Correct answer: The feature may range from 24.95 to 25.05 units
The ± 0.05 tolerance means the actual dimension may be 0.05 units above or below the nominal 25.00, giving an acceptable range of 24.95 to 25.05.
Question 2: In a standard weld symbol on a blueprint, the arrow side of the reference line indicates what?
- The weld is to be done by a certified welder only
- The weld symbol applies to the joint side the arrow points to (Correct answer)
- The weld is a full-penetration weld
- The direction the welding torch travels
Correct answer: The weld symbol applies to the joint side the arrow points to
The arrow on a weld symbol points to the specific joint, and weld information below the reference line applies to the arrow side of the joint.
Question 3: What does the notation 'TYP' (or 'TYP.') mean when it appears next to a dimension on a blueprint?
- The dimension is approximate only
- The dimension applies to all identical features throughout the drawing (Correct answer)
- The tolerance is tighter than standard
- The feature is optional
Correct answer: The dimension applies to all identical features throughout the drawing
'TYP' (typical) means the dimension or feature shown applies equally to all similar or identical features on the drawing, avoiding repetitive dimensioning.
Question 4: What type of line is used to indicate a cutting plane in a section view drawing?
- A thin solid line
- A thick chain line with arrowheads showing the viewing direction (Correct answer)
- A dashed thin line
- A wavy freehand line
Correct answer: A thick chain line with arrowheads showing the viewing direction
Cutting plane lines are drawn as thick chain lines (long dashes with short dashes) with arrowheads at each end indicating the direction of sight for the section view.
Question 5: On a mechanical blueprint, what does the surface finish symbol (a check-mark-like symbol) indicate?
- The surface has passed quality inspection
- The required texture or roughness of a machined surface (Correct answer)
- The surface is to be painted
- The surface is a mating or joining surface only
Correct answer: The required texture or roughness of a machined surface
Surface finish symbols specify the required surface texture, roughness, and lay of a machined surface, typically measured in micrometers (µm) or microinches (µin).
Question 6: What is an isometric drawing used for in industrial trades?
- Showing only one flat face of an object with true dimensions
- Representing a 3D object in a 2D drawing using 30° axes for a pictorial view (Correct answer)
- Showing internal components through a cutting plane
- Depicting the assembly sequence of parts
Correct answer: Representing a 3D object in a 2D drawing using 30° axes for a pictorial view
Isometric drawings display three faces of an object simultaneously using 30° angles from horizontal, giving a three-dimensional pictorial representation without perspective distortion.
Question 7: On a piping or mechanical blueprint, what does the abbreviation 'NPS' stand for?
- Normal Pipe Size
- Nominal Pipe Size (Correct answer)
- National Plumbing Standard
- Non-Pressure System
Correct answer: Nominal Pipe Size
NPS (Nominal Pipe Size) is the North American standard designation for pipe sizes; the nominal diameter is a reference number that does not necessarily equal the actual pipe diameter.
OIT Blueprint Reading and Technical Drawing 2
On a blueprint dimension, what does a tolerance notation of '25.00 ± 0.05' indicate?