AIT Blueprint Reading 5

Question 1

When a blueprint dimension shows '3/4" – 10 UNC – 2B', what does this callout describe?

Accepted Answer

A 3/4-inch diameter screw thread, 10 threads per inch, Unified National Coarse, class 2 fit (internal)

Answer

This thread callout specifies a 3/4-inch diameter, 10 TPI (threads per inch), Unified National Coarse series, Class 2 fit for an internal (female) thread.

Question 2

What does a zigzag or wavy break line on a blueprint indicate?

Accepted Answer

A long object that has been shortened to fit on the drawing

Answer

A break line (wavy or zigzag) indicates that a long object has been shortened on the drawing while maintaining the correct overall dimensions in the notes.

Question 3

In a floor plan blueprint, what does the symbol of a thin rectangle with diagonal lines inside typically represent?

Accepted Answer

Insulation within a wall cavity

Answer

In construction drawings, a rectangle with diagonal hatching inside a wall cavity represents batt insulation.

Question 4

What is a 'datum' in the context of blueprint dimensions and GD&T?

Accepted Answer

A theoretically exact reference point, axis, or plane from which measurements are taken

Answer

A datum is an exact reference feature (point, line, or plane) used as the starting point for measurements and geometric tolerances on a part.

Question 5

On a blueprint callout reading '4X Ø0.500 ↧ 0.750', what does the '4X' signify?

Accepted Answer

There are four identical holes to be machined

Answer

'4X' before a feature callout means the operation or feature is repeated four times (four identical holes of 0.500" diameter drilled to 0.750" depth).

(AIT) Apprenticeship and Industry Training Practice Test

(AIT) Apprenticeship and Industry Training Practice Test

AIT Blueprint Reading 5