Mechanical Drawing Fundamentals

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D R A W I N G S M A D E W I T H P R E C I S I O N D R A W I N G

I N S T R U M E N T S .

Drawing equipment: Drawing board, T square,triangles, scales, erasers and shields, dustbrushes, tape, compass, bow instruments,drawing paper, vellum

1.

S E T U P T H E P A P E R

Set up a piece of paper on the board: 1" from theleft side, at least 4" from the bottom. Equallyspaced top to bottom works well.

1.

Hold the t square high up on the paper, againstthe left edge of the board.

2.

Use the left hand to hold the t square against the

board edge firmly, but not tight.

3.

Also with the left hand, smooth the t square bladeto the right, and press firmly against the paper.

4.

Tape the top left corner; smooth the paper out ifnecessary, and tape the lower right corner.

5.

Tape the remaining corners.6.

Left handers, work with the t square against theright edge of the board.

7.

S H A R P E N T H E P E N C I L :

Never sharpen over the drawing board,

Dress the lead down to a long symmetrical cone

Use the sandpaper pads

Practice it now.

T H E A L P H A B E T O F L I N E S

3 distinct thicknesses of lines

Thick (border lines, visible lines, cutting-planelines and short break lines)

hanical Drawing Fundamentals http://www.arps.org/users/hs/moriartm/cad/general/mechanical_drawin...

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Medium (hidden lines)

Thin (long break lines, section lines, center lines,dimension lines, extension lines and phantomlines)

All lines except construction lines should be denseblack

Never fuzzy, gray or unclear

Construction lines should always be extremelylight. Barely viewed at arm's length.

D R A W I N G H O R I Z O N T A L L I N E S

Set the pencil at about 60 with the paper, whilekeeping the pencil in the vertical plane.

Line will not be straight if the pencil is tilted away

from this position.

Draw the line from left to right, holding the tsquare against the board edge, and across theblade as before.

Little finger of the pencil hand guides lightly alongthe t square blade

Simultaneously, rotate the pencil slowly bypressing the thumb forward, to roll the pencil.


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Prevents the pencil from wearing down in oneplace, which would change the uniformity of theline.

Do not draw lines along the lower edge of the tsquare.

Practice it now.

D R A W I N G V E R T I C A L L I N E S

Use either of the two triangles

Vertical side of the triangle is on the left.

Left handers turn it around.

Hold the head of the t square firmly against theboard edge.

Slide the left hand across the blade to the place

where you want to draw a vertical line.

Position the triangle on the blade.

Set the pencil at about 60 with the paper, whilekeeping the pencil in the vertical plane.

Rotate the pencil slowly by pressing the thumbforward, to roll the pencil.

Draw the line upward.

Practice it now.


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U S I N G T H E T R I A N G L E S

45 triangle

30 x 60 triangle

All vertical lines and most inclined lines are drawnwith these

I N C L I N E D L I N E S

Draw lines at 45

Position the triangle on the t square and draw theline.

Use the long position for long lines

Use the short position for shorter lines. Thisposition is more rigid, stable and therefore more

accurate.


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Draw lines at 30 and 60

Position the triangle on the t square and draw the

line.

Use the long position for long lines

Again, use the short position for shorter lines. Thisposition is more rigid, stable and therefore moreaccurate.


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If 2 triangles are combined, lines may be drawn at15 or 75.

The entire 360 can be divided into 24 sections of

15 with the t square and the triangles.

P A R A L L E L L I N E S

Can easily draw parallel lines at any of thestandard angles by sliding the triangle along the tsquare and repeating lines.

To draw a line parallel to any line flip the t squareover, move the t square and triangle over until thehypotenuse of the triangle lines up with the givenline.

Then while holding t square firmly in place, slidethe triangle to position and draw the line.


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P E R P E N D I C U L A R L I N E S

To draw a line perpendicular to any given line,move the t square and triangle until a side of thetriangle lines up with the given line.

Then, while holding the t square in place, slide thetriangle across the given line and draw theperpendicular line.


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B L O C K I N G I N T H E O B J E C T

Use construction lines to block in and layout thedrawing

Construction lines are very light, drawn with littlepressure applied to the pencil.

Use the scale to measure and mark off thebeginning points for all vertical and horizontallines.

Draw the construction lines lightly.

D A R K E N I N G L I N E S O F T H E C O M P L E T E D O B J E C T

First darken in lines created with a compass

It is easier to match the weight of that line than itis to try to match the weight of straight lines withthe compass, if the compass lines were darkenedafter the straight lines.

Next darken irregular curved lines.

Then darken inclined lines.

Finally darken vertical and horizontal l ines.

Start at the top of the drawing and move down asyou darken lines.

Always move away from lines that have just beendarkened.

Brush off excess graphite after each type of linehas been darkened.

E R A S I N G

Do not draw a line until you are sure you need it.

When erasing, be careful not to spoil the drawing.

Avoid making careless, dirty pencil drawings andthen doing a lot of erasing before heavying-in thefinal lines.

Use the erasing shield to protect line near the lineto be erased.

Brush off eraser residue with the brush rather thanusing your hand.

Practice erasing lines and brushing off thedrawing.


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N E A T N E S S

Essential to quality drawing

Take your time to be neat from the beginning.

Avoid letting pencil dust particles build up on the

drawing. Brush it off periodically.Keep your pencil sharp!

Keep your hands and equipment clean.

Do everything you can to keep the drawing frombeing smeared.

Beware of the oils and sweat in our hands on thedrawing.


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The habit of accuracy is important.

Place the scale along the line to be measured.

If no line exists, draw a construction line.

With your eye directly above the correct mark onthe scale, make a short dash at right angles to the

scale.

Double check the measurement after setting off adimension.

For horizontal measurements, place the scale onthe paper so that the scale in use in on the top.

For vertical measurements, place the scale so thatthe scale in use is on the left.

If a series of measurements is to be set off end toend, do not set off the first dimension and thenmove the scale to start the next dimension from 0.

All the measurements should be set off withoutmoving the scale.

So, it is important to study the scale and learnhow to add fractions using it.

S H E E T L A Y O U T

After the sheet has been attached to the board,

layout the sheet as described and shown in theimage below.

Draw a light horizontal trim line 1/4" from thebottom of the sheet.

Draw a vertical trim line 1/4" from the left edge.Use a triangle to draw the vertical lines.

Set off all width dimensions along the lower trimline. The full size scale should be up.

Set off all height dimensions along the left trimline. The full size scale should be to the left.

Draw horizontal construction lines through themarks at the left side of the sheet.

Draw vertical construction lines from the bottomupward, using a triangle, through the marks at thebottom of the sheet.

Retrace border and title strip to make the linesheavier.


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P R A C T I C E P R O B L E M S

Follow the directions to complete the inlaidlinoleum design drawing.

Then select one other design to draw and makeanother drawing on a second sheet.

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Mechanical Drawing Fundamentals