Blueprint Reading: Lines, Views, Dimensions, and Specifications

Vocabulary practice flashcards covering engineering drafting, line types, orthographic projection, dimensioning standards, tolerances, scales, thread specifications, and bills of materials.

Object Line

A thick solid line used to show the visible shape and edges of an object.

Hidden Line

A broken line that shows edges and surfaces not visible to the eye.

Center Line

A broken line made of alternating long and short dashes that shows the center of a circle, arc, or symmetrical areas.

Dimension Line

A fine line with an arrow or dash at each end that shows the distance or size being dimensioned.

Extension Line

A thin straight line extending outward from an object to show a dimension point.

Leader Line

A fine line drawn at an angle with an arrow or dot that points to a surface to provide dimensions or add notes.

Chain Line

A heavy broken line made of long and short dashes that indicates the location and extent of a surface area.

Long Break Line

A ruled light line featuring zigzags used to conserve space on a drawing by indicating a long break.

Orthographic Projection

A drawing system that shows the exact form of an object by projecting different views, typically aligned horizontally and vertically.

Front View

The primary view in orthographic projection that provides the best indication of the object's shape and detail.

Orthographic View Arrangement

The standard placement where the top view is lined up directly above the front view, and the right side view is lined up directly to the right of the front view.

Notes

Lettered information written in CAPITAL LETTERS providing construction details and extra information needed to make parts.

Local Note

A note applying to a particular part or specific location on an object; placed near the view and uses a leader to point to the exact location.

General Note

A note applying to the drawing as a whole; placed in an open space away from the views.

Specification Notes

Notes located near the view they refer to that specify construction details such as required material, welding process, and the type or size of electrodes and welding rods.

Title Block

The identification card of a drawing that includes details such as part name, quantity required, order number, material, scale size, general specifications, drafter, checker, drawing number, date, tolerances, company name, and revision record.

Standard Drawing Sheet Sizes

Standard paper sizes defined as: Size A ($8\frac{1}{2}'' \times 11''$), Size B ($11'' \times 17''$), Size C ($17'' \times 22''$), Size D ($22'' \times 34''$), and Size E ($34'' \times 44''$).

Linear Dimensions

Measurements indicating length or distance, expressed as whole numbers, fractions (commonly used on weld drawings), or decimals (preferred for machining and precision work).

Angular Dimensions

Dimensions used when a line or edge is at an angle, usually shown in degrees ($^\flat$ or $^\times$ notation/degrees, minutes, and seconds) measured horizontal to vertical or angle to angle.

Bevel

A sloping edge extending along all or part of an edge prepared specifically for welding purposes.

Feather Edge

A sharp edge formed by the slope of a bevel.

Root Face (Land)

The flat, unsloped area remaining along the edge of a beveled part.

Chamfer

A beveled or sloping edge that is the exact same shape as a bevel, but manufactured for purposes other than welding.

Radius ($R$)

The dimension measured halfway across a circle or arc, indicating both location and size when corners or ends are rounded.

Diameter ($\varnothing$, $D$, or $\text{Dia}$)

The dimension measured the entire way across a circle.

Drilled Hole Callout

A note or leader pointing to a hole view giving three pieces of information: diameter (size), depth (drilled to depth or 'thru'), and the number ($\#$) of identical holes required.

Drill Bit Size Designations

Four methods to specify drill size on a drawing: a letter (e.g., 'F'), a number (wire gauge), a fraction (most common), or a decimal.

Tolerance

The permitted variation or allowable error in a dimension, specifying how much a finished measurement can be over ($+$, plus) or under ($-$, minus) to ensure parts fit properly.

Default Standard Tolerances

Allowable variations applied unless otherwise noted: Fractions ($\pm \frac{1}{8}''$), Decimals ($\pm 0.005''$), and Angular ($\pm 2^\times$).

Full Scale

A drawing scale of $1'' = 1''$, where the drawn object matches the exact size of the actual object in real life.

Reduced Scale

A scale where the drawing is smaller than the actual object (e.g., $\frac{1}{4}'' = 1'\text{-}0''$ or $\frac{1}{8}'' = 1'\text{-}0''$), commonly used for large objects and prints.

Enlarged Scale

A scale where the drawing is larger than the actual object (e.g., $\frac{1}{2}'' = \frac{1}{8}''$, making the drawing $4\times$ larger than real life), useful for showing small details.

Conventional Dimensioning

A dimensioning method giving overall dimensions of length and height, where intermediate dimensions not directly specified can be found by adding conventional dimensions together.

Baseline Dimensioning (Running Dimensioning)

A dimensioning method in which all dimensions originate from a single base reference line, such as a machined surface, centerline, symbol, or datum.

UNC

Unified National Coarse; a standard form designation for coarse screw threads.

UNF

Unified National Fine; a standard form designation for fine screw threads.

Class of Fit

A thread specification designating fit tightness: Class 1 (loose fit), Class 2 (standard fit), or Class 3 (precise, tight fit).

Thread Specification Elements

The breakdown of a thread callout (e.g., $\frac{3}{4}\text{-}10\text{ UNC-3 LH}$): thread diameter ($\frac{3}{4}''$), threads per inch ($10$), thread form (UNC), class of fit ($3$), and thread direction (LH = Left Hand).

Actual Size

The measured, as-built dimensions of a fabricated part.

Nominal Size

The approximate or commercial size designation of a part or material (e.g., lumber dimensions).

Dual Dimensions

The practice of displaying both imperial and metric dimensions side-by-side on a print, allowing the manufacturer to use either system.

Bill of Materials (BOM)

A table or list on a drawing specifying all parts and materials needed to assemble an object, detailing Item/Part Number, Quantity (QTY), Description, and Material Size.