Technical Drawing Flashcards

What is the correct reading direction for a unilateral tolerance such as +0.005 / -0.000?

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.

On a welding symbol, where is the reference line drawn?

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.

What does an 'R' prefix before a dimension value indicate?

Answer: The feature is a radius

The prefix 'R' designates a radius dimension, measured from the center of the arc to its circumference.

In a thread callout '1/2-13 UNC-2A', what does '2A' specify?

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.

What information is typically found in the title block of a technical drawing?

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.

A phantom line (long dash, two short dashes) is commonly used to show:

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.

When dimensioning a drawing using the baseline (datum) method, all dimensions originate from:

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.