Mechanical drawings Mechanical drawings like Figure 2 show outlines of parts, assemblies, and critical
dimensions; assembly and machining notes; and materials used for manufacturing
the parts.
Drawings ________ have been used for centuries in technical applications, and were mostly
produced by people skilled in drawing, or drafters. Drawings were made
mechanically, that is, with pencil or pen with paper on drafting boards,
Image: Drawings
Diazo printing process The next reproduction method was the diazo printing process, which made
copies with white backgrounds and dark lines. The diazo process produced
originals on a special thin drafting paper called vellum, linen paper, or polyester
film.
Modern computer-aided drafting (CAD) Modern computer-aided drafting (CAD). Drawings are now made on computers,
using specialized software, as shown in Figure 3. CAD operators store drawings
electronically on a computer hard disk, so they can be easily retrieved and
modified if required. Once the drawing is complete, it can be printed on a
conventional printer or else plotted in multiple colors on a wide-format plotter.
Title Block A table located in the bottom right-hand corner of an engineering drawing that
identifies, in an organized way, all of the necessary information that is not given on
the drawing itself. Also referred to as a title strip.
, Blue Print Reading Exam
Drawing Scales Drawing scales can range from very large to very small, including full size. For
large objects, such as ships and buildings, all dimensions must be reduced to a
suitable scale that can be represented on the paper. For very small objects, such
as the components of a watch or cell phone, the parts need to be shown much
larger than actual size so that dimensions and other information can be shown
next to the parts.
Understanding Drawing Scales The scale can be denoted as a ratio, such as 4:1 or 1:2; or as a conversion such as
1/2 = 1 or 1-1/2 = 1. Full scale would be 1 = 1 or 12 = 1, etc.
- Here's how to interpret a scale: the first number is the number you would
physically measure on the print; the second number is the actual dimension of the
part. So a scale given as 1/2 = 12 means that for every 1/2 inch you measure on the
print, the actual dimension is 12 inches. inches.
- At this scale, a dimension measured as 2-1/2 on the drawing is actually 60 on the
real part.
______ drawings Detail drawings are drawings of individual parts.
______ drawings Assembly drawings show the arrangement of individual parts that make up the
assembly, as well as how the parts fit together, and give notes for the people who
will actually assemble the par
_____ drawings For construction work or steel fabrication, working drawings refer to the set of
prints used to construct a building, piping assembly, bridge, or other structure.
The Symbol Ø the symbol Ø means a diameter. Ie. The dimension number Ø.500 means the
inside diameter of the hole in the part is 0.500 inches
, Blue Print Reading Exam
(BOM) Bill Of Materials Assembly drawings also usually include a bill of materials (BOM). This is a list of
the individual parts and subassemblies that make up that assembly.
What Mechanical Means in relation to: Most of us use the word "mechanical" to mean mechanical parts, such as gears,
brackets, pistons, springs, and other parts used in manufactured products.
But in regard to buildings or architectural applications, "mechanical" refers to the
electrical; heating, ventilating, and air conditioning (HVAC); and plumbing and
piping components.
A building contractor or architect refers to drawings for these systems as
"mechanical drawings."
Revision Block Drawings always have a _______ block that records all changes done at a certain
time, the drafter who did the changes, and the date the changes were made
Extentsion Line __________ lines are lines that extend from part features such as edges or centers of
holes. They don't touch the object itself, but have a small break between the part
and the beginning of the extension line. Extension lines are most often used for
dimensioning part features.
Object Lines _______ lines, sometimes called visible lines, are thick black lines that outline the
shape of the part. They're the edges of part features you would see if you had the
real part in front of you. They're unbroken and solid.
, Blue Print Reading Exam
Hidden Lines _______ lines are broken dashed lines that show edges you wouldn't be able to see
without x-ray vision. Hidden lines show the relationship of these invisible features
to the visible edges and features.
Section lines _______ lines are thin unbroken lines that show a part has been cut for viewing on
edge.
Dimension lines _______ lines are used with arrowheads to show dimensions between features.
They're usually used with extension lines that extend from part features such as
edges or centerlines to show distance relationships.
Leader Lines ________ lines are thin, solid lines leading from a note or dimension line. An
arrowhead touches the part and extends to the note or dimension. Leader lines
are used for assembly notes or to give information about details such as multiple
(or repetitive) features, and are often used for dimensioning radii and diameters.
.A simple shaft is 1/2 inch in diameter and 2.75 inches Ratio 1:2 MEANS THE PARTS ARE SMALLER THAN THEY APPEAR
long. If a drafter wants to draw the part at a 1:2 scale, on 1/2 divided by 2 = .25 inches
paper the part will be _______ inch(es) in diameter and _______ 2.75 divided by 2 = 1.375 inches long
inch(es) long.