Sacramento City College EDT 300/ENGR 306 · 6 EDT 300/306 - Chapter 3 - Use/Care of Drafting...

EDT 300/306 - Chapter 3 - Use/Care of Drafting Equipment 1

The Use and CareThe Use and Care of of

Drafting EquipmentDrafting Equipment

Chapter 3Chapter 3Sacramento City College

EDT 300/ENGR 306

2 EDT 300/306 - Chapter 3 - Use/Care of Drafting Equipment

Objectives Objectives Learn to properly and efficiently use basic drafting tools and equipment to produce technical drawings.


Basic Manual Drafting EquipmentBasic Manual Drafting EquipmentVocabulary

Acute angleAlphabet of LinesAngleCircumferenceCompassDrafting FilmErasing ShieldsInclined

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India ink•

Irregular curves•

Obtuse angle•

Opaque•

Protractor•

Right Angle•

Scales•

Symmetrical•

T-Square•

Transparent•

Vellum•

Vertex


Basic Manual Drafting EquipmentBasic Manual Drafting EquipmentDrafting BoardT-Square or parallel-ruling straight edge or drafting machineDrawing sheets (paper, cloth, or film)Drafting tapeDrafting pencilsPencil SharpenerErasing shieldTriangle, 45o and 30o-60o

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Architect’s, engineer’s and metric scale

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Irregular curve•

Drawing instrument set

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BrushBlack drawing inkTechnical pens


Basic Manual Drafting EquipmentBasic Manual Drafting EquipmentDrawing tables and desks

Come in many different sizes and shapesCan be used standing or sittingCombination drafting table, desk and regular office chair is the most comfortable and efficient.See Figure 3-3.


Drawing Boards Drawing Boards Drawing sheet is taped to the drawing board.Drawing boards usually measure:

9 x 1216 x 2118 x 24Usually made of pine or basswoodMade to stay flat and so the guiding edge will remain straightHardwood or metal strips are used on some board edges to provide more durable edges.


TT--SquaresSquaresA T-Square

is an instrument that consists of a head that lines up with a true edge of the drafting board and a blade, or straightedge, that provides a true edge.Most have plastic-edged wood or clear plastic blades and heads of wood or plastic.If extreme accuracy is required, the T-square may be made of stainless steel.

The blade must be very straight.The blade must be attached securely to the top surface of the T-head.

See Figure 3-4.


Checking TChecking T--Square AccuracySquare AccuracyTo check the accuracy of a T-square

On a clean sheet of paper, draw a sharp, thin line along the drawing edge of the T-square.Then, turn the drawing sheet around and line up the drawing edge of the T-square with the other side of the line.If the drawing edge and the pencil line do not match, the T-square is not accurate and should be replaced.See Figure 3-5.


Drafting MachinesDrafting MachinesTwo kinds are in use

The arm or elbow type (Figure 3-6).The track type (Figure 3-9).The parallel bar type (Figure 3-9).


Arm or Elbow Drafting MachineArm or Elbow Drafting MachineThe anchor and two arms hold a movable protractor head with two scales.

The scales are normally at right angles to each other.The arms allow the scales to be moved to any place on the drawing that is parallel to the starting position.Items are parallel when their edges are exactly the same distance apart at all points.


Arm or Elbow Drafting MachineArm or Elbow Drafting MachineMost industrial drafting departments and many schools use drafting machines.Drafting machines combine the functions of the T-square, triangles, scales, and protractor.

Allow you to draw more quickly and with less work.


TrackTrack--Type Drafting MachineType Drafting MachineThe track-type uses a horizontal guide rail at the top of the board and a moving arm rail at right angles to the top rail.

An adjustable protractor head and two scales, usually at right angles, move up and down on the armThe scales may be moved to any place on the drawing that is parallel to the starting position.This type of drafting machine is easy to use on large boards or on boards placed vertically or at a steep angle.


Other Basic Tools Other Basic Tools Triangles

Drafters use two types of triangles in combination with the T-square to draw lines at various angles.

ProtractorA protractor is an instrument that is used to measure or lay out angles.

Parallel-Ruling StraightedgesMany drafters prefer this device to the drafting machine.


Other Basic Tools Other Basic Tools Irregular Curves

Also called French curvesUsed to draw noncircular curvesThey are made of sheet plasticCome in many different formsSets are made for ellipses, parabolas, hyperbolas, and other special purposes.

Flexible curvesCurves which can be adjusted to complex curves that may be difficult to draw with other irregular curves.


Drawing MediaDrawing MediaDrawings are made on may different materials.


PaperPaperWhite, tinted, blue tint or pale green.

White is used for drawings which will be photographed.Light colored papers reduce eyestrain and are less likely to soil.

Opaque drawing papers are used for Permanent recordsMaster drawings.Maps.Any drawing that will be photographed.


Tracing paper Tracing paper Tracing paper

Is translucent drawing paperName was derived from the practice of first making a drawing in pencil on opaque paper, then “tracing” in ink on a sheet of translucent paper.Translucent papers allow “bluelines” or copies to be made.Natural papers made strong and durable are not very transparent.Papers with high transparency are only moderately durable.


VellumVellumVellum

Is tracing paper that has been treated to make it more transparent.

Vellum provides strength, transparency, durability (handling and folding) and erasability without “ghosting”.


Tracing ClothTracing ClothTracing Cloth

Is finely woven cotton fiber material cloth that has been sized with starch to provide a surface that takes pencil and ink.It comes in white for pencil tracings and blue for ink.



The working side is dull or frosted.

You can erase without damaging the surface by using a soft rubber or vinyl eraser.

Treated to provide a good working surface and good transparency.

Is considerably more expensive than paper media.



Is subject to expansion and shrinkage. The drawing should be completed all at once.


Mylar (Plastic Film)Mylar (Plastic Film)Best qualifications for drawing media.Best for longevity, dimensional stability, great resistance to tearing, easy erasing with soft eraser and high transparency.Waterproof.Will not become brittle with age.Drawing surface is matte (dull and rough).Other side is very smooth, and will not accept graphite.


Drawing Sheet SizesDrawing Sheet SizesDrawing sheets follow standards set by

American National Standards Institute (ANSI)

ORInternational Standards Organization (ISO)


ANSI Sheet SizesANSI Sheet SizesAmerican National Standards Institute (ANSI) provides two sets of standards which are commonly called the US Customary series.Both are developed upward in size from smallest to largest.

8.5 x 11 seriesOR

9 x 12 series


ANSI Sheet SizesANSI Sheet SizesSeries based on 8.5” x 11” sheet.

A - 8.5” x 11.0”B - 11” x 17”

(keep the longest dimension (11); multiply the smallest dimension by 2; 2 x 8.5 = 17)

C - 17” x 22”(keep the longest dimension (17); multiply the smallest dimension by 2; 2 x 11 = 22)

D - 22” x 34”(keep the longest dimension (22); multiply the smallest dimension by 2; 2 x 17 = 34)

E - 34” x 44”(keep the longest dimension (34); multiply the smallest dimension by 2; 2 x 22 = 44)


ANSI Sheet SizesANSI Sheet SizesSeries based on 8.5” x 11” sheet.

A - 8.5” x 11.0”B - 11” x 17”C - 17” x 22”D - 22” x 34”E - 34” x 44”


ANSI Sheet SizesANSI Sheet SizesSeries based on 9” x 12” sheet.

A - 9” x 12.0”B - 12” x 18”

(keep the longest dimension (12); multiply the smallest dimension by 2; 2 x 9 = 18)

C - 18” x 24”(keep the longest dimension (18); multiply the smallest dimension by 2; 2 x 12 = 24)

D - 24” x 36”(keep the longest dimension (24); multiply the smallest dimension by 2; 2 x 18 = 36)

E - 36” x 48”(keep the longest dimension (36); multiply the smallest dimension by 2; 2 x 24 = 48)


ANSI Sheet SizesANSI Sheet SizesSeries based on 9” x 12” sheet.

A - 9.0” x 12.0” sheet.B - 12” x 18”C - 18” x 24”D - 24” x 36”E - 36” x 48”


ISO Sheet SizesISO Sheet SizesISO Sheet sizes

are developed downward in size from a base sheet with an area of about 1 square meter.

(Remember that ANSI sizes are developed upward)

Sheet sizes are based on a length-to-width ratio of 1 to square root of 2.Each smaller size has an area equal to one-half the preceding size.


Setting up a Drawing on the Drafting Setting up a Drawing on the Drafting BoardBoard


Fastening The Drawing Sheet To the BoardFastening The Drawing Sheet To the BoardPlace sheet at least 2” from left edge.

Place sheet at least 4” to 6” from the bottom of the drawing table.

Line up sheet horizontally with drafting machine then place drafting machine over paper to hold in place.

Use strips of tape or round “draft-dots” to hold the sheet in place.


PencilsPencilsPencil “lead” is made from graphite, a form of the element carbon.

It also contains clay, and some resins to hold it togetherGraphite pencils have been used for more than 200 years and are still the most important kind.


Pencils Pencils Leads used in drawing pencils are manufactured by a special process designed to make them strong and capable of producing sharp, even density lines.


Graphite Pencil Grades of HardnessGraphite Pencil Grades of Hardness6B-softest and blackest5B-extremely soft4B-extra soft3B-very soft2B-soft, plusB-softHB-medium softF-intermediatebetween hard and soft

H-medium hard2H-hard3H-hard, plus4H-very hard5H-extra hard6H-extra hard, plus7H-extremely hard8H-extremely hard, plus9H-hardest


Choice of Pencil HardnessChoice of Pencil HardnessThe grade of pencil you used depends

On the kind of surface on which you are drawing.

The roughness of the drawing mediaPaperVellum

On how opaque (dark) and thick you want the finished line to be.


Common Use of Harder LeadsCommon Use of Harder LeadsThe softer grades of lead

deposit more lead on the media and produce more opaque lines.

However, many drafters continue to use the harder grades because

they produce sharper lines and do not smudge readily during drafting process.


Choice of Pencil HardnessChoice of Pencil HardnessExamples“Layout views on fairly hard-surfaced drawing paper”.

4H or higherTracing paper/finished views to be reproduced.

H or 2H

Grades HB, F, H are sometimes used for sketching, and for drawing arrowheads, border lines.


Choice of Pencil HardnessChoice of Pencil HardnessThe exact grade depends on the drawing and the surface.Very hard and very soft leads are seldom used in drafting.


Sharpening PencilsSharpening Pencils


Sharpening PencilsSharpening PencilsTo sharpen a wooden pencil,

Cut away the wood at a long slope (Fig 3-17A) orUse a drafter’s pencil sharpenerSharpen the end opposite the grade markLeave about .38” to .5” exposed.Shape the lead to a long conical point

Do this by rubbing the lead back and forth on a sandpaper pad, while turning the pencil slowly.Burnish the lead by rubbing on drafting paper.

Never sharpen a pencil over a drawing board !


Two Pencil Point Types Two Pencil Point Types Conical

The conical point is used for general line work and lettering.It is shaped in a lead pointer

WedgeUsed for drawing ling straight lines because it holds it point (edge) linger than the conical point.


Lead HoldersLead HoldersAre widely used by drafters

They hold plain sticks of lead in a chuck that allows the exposed lead to be extended to any length desired.

Generally are shaped just like pencilsThe lead is sharpened in a lead sharpener.


Pencil TechniquePencil Technique


Pencil TechniquesPencil TechniquesLines

must ALWAYS be clean and sharp.must be dark enough for the views to be seen when standard line widths are used.


Pencil TechniquesPencil TechniquesPencil pressure

Too muchand you will groove the drawing surface

Not enoughthe line will be too light and will be “fuzzy”.

Sufficient pressure must be used to fill the drawing fibers with graphite.


Pencil TechniquesPencil TechniquesPencil Strokes

More than one pencil stroke is required to produce a line of proper density

The pencil MUST BE ROTATED as you are drawing the line.


Pencil TechniquesPencil TechniquesDevelop the habit of turning the pencil between your thumb and forefinger when drawing a line.

This will helpkeep the line uniform and keep the pencil point from wearing unevenly.


Erasers and ErasingErasers and ErasingUse soft erasers

Vinyl type (only).Pink/green erasers are too abrasive.

On film, only use a vinyl type of eraser.

On paper or cloth, erase across the direction of the line.


Erasing Procedure Erasing Procedure Clean eraser by rubbing on a clean scrap of paper.

With your free hand, hold the drawing securely.Rub soft vinyl eraser lightly back and forth to erase detail or line.

For erasing deeply grooved pencil or ink lines, place a triangle under the paper for backing.

If necessary to protect details close by, use an erasing shield.


Eraser Shields Eraser Shields Use eraser shields to prevent accidentally erasing nearby lines.

Erasing shields are made of metal, or plastic and have openings of different sizes and shapes.

Position the shield so only the part you wish to erase appears in one of the openings on the shield.


Electric ErasersElectric ErasersUse care not to remain in one spot too long, especially with film.

You can “polish” the film to the point that it will no longer accept graphite.

Use only soft rubber or vinyl erasers.

A very gentle pressure avoids overheating the drawing surface.

You can use a piece of thin gauge copper, brass or aluminum sheet under the area to be erased to help dissipate the heat and reduce the possibility of damage to the drawing.


Neatness In DraftingNeatness In DraftingNeatness = Ability

The first impression is a lasting one.Practice cleanliness from the start. The primary source of “dirty” drawings is smeared graphite

Sliding T-squares, triangles, shirt sleeves and hands across drawings.

Lift tools off your work; do not slide!


Neatness In DraftingNeatness In DraftingWash your hands before starting, and occasionally during drawing if your hands tend to be oily.

Always wipe dust and dirt from instrumentswith a soft cloth before starting to draw and frequently during use.

Lay out all views with a hard pencil first. “Heavy-in” lines only when certain they are correct.


Neatness In DraftingNeatness In DraftingRemove graphite dust when it collects.

After each line is drawn, blow loose graphite from the sheet.

Remove erasure dust with a brush, not your hands!


Neatness In DraftingNeatness In DraftingDO NOT slide instruments across drawing!

Lift the drafting machine prior to moving.

Sharpen pencils away from the drawing.

Maintain an orderly drawing area.Keep only the tools you need on top of the deskKeep unused tools OFF THE SHEET!

Sacramento City College EDT 300/ENGR 306 · 6 EDT 300/306 - Chapter 3 - Use/Care of Drafting...

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