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<\/p>\n\u00a0Week 4; drawing instrument<\/p>\n
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\u00a0Chapter – 1A
\nDRAWING INSTRUMENTS
\nAND THEIR USES
\nDrawing Instruments are used to prepare neat and accurate Drawings. To a greater extent, the ac-
\ncuracy of the Drawings depend on the quality of instruments used to prepare them. The following is the list
\nof Drawing Instruments and other materials required.
\na)
\nDrawing Board
\nb)
\nT-square or Drafter (Drafting machine)
\nc)
\nSet Squares
\nd)
\nProtractor
\ne)
\nDrawing Instrument Box
\nf)
\nDrawing Sheet
\ng)
\nDrawing Pencils
\nh)
\nDrawing Pins\/Clips
\na) Drawing Board :
\nDrawing board is made from strips of well seasoned soft wood generally 25 mm thick. It is cleated
\nat the back by two battens to prevent warping. One of the shorter edges of the rectangular board is pro-
\nvided with perfectly straight ebony edge which is used as working edge on which the T-square is moved
\nwhile making Drawings.
\nBattens
\nWorking edge
\n(ebony)
\nFig. 1A.1
\nNote:
\nWhen Minidrafter (Drafting machine) is used to prepare Drawings, the working edge is not
\nused.
\n2
\nComputer Aided Engineering Drawing
\nDrawing board size:
\nDrawing boards are made in various sizes. The selection of Drawing board depends on the size of
\ndrawing paper used. The sizes of Drawing board recommended by Bureau of Indian Standards (B.I.S) is given
\nbelow
\nStandard size of Drawing boards
\nDesignation
\nSize (mm)
\nDesignation
\nSize (mm)
\nB0
\n1500 \u00d7 1000
\nB3
\n500 \u00d7 350
\nB1
\n1000 \u00d7 700
\nB4
\n250 \u00d7 350
\nB2
\n700 \u00d7 500
\nb) T-square :
\nT-squares are made from hard wood. A T-square consists of two parts namely the stock and the
\nblade joined together at right angles to each other by means of screws and Pins as shown in figure 1A.2. The
\nstock is made to slide along the working edge and the Blade moves on the Drawing board.
\nWo r k i n g e d g e
\nBlade
\nStock
\nScrews
\nFig. 1A.2
\nThe working edge of T-square is used to draw parallel lines, vertical lines or inclined lines at 30
\n\u00b0
\n, 60
\no
\nto the horizontal using set squares.
\nDrafting machine (or Drafter):
\nIn a Drafting machine, the uses and advantages of T-square, set square, scales, protractors are
\ncombined. One end of the Drafter is clamped at the left top end of the Drawing board by a screw provided
\nin the drafter.
\nAn adjustable head with a Protractor is fitted at the other end of the Drafter. Two blades made of
\ntransparent celluloid material are fitted to the adjustable head and are perfectly perpendicular to each other.
\nThese blades are used to draw parallel, horizontal, vertical and inclined lines. The blades always move parallel
\nto the edges of the board. Use of Drafting machine helps in reducing the time required to prepare Drawing.
\nDrawing Instruments and their Uses
\n3
\nScale
\nScale
\nPotractor
\nAngle
\nDrawing sheet
\nDrawing board
\nParallel bar arm
\nParallel bar arm
\nFig. 1A.3
\nc) Set Squares :
\nSet squares are generally made from Plastic or celluloid material. They are triangular in shape with
\none corner, a right angle triangle. A pair of set squares (30
\n\u00b0
\n\u201360
\n\u00b0
\n) and 45
\n\u00b0
\n(45
\n\u00b0
\nset square are generally pro-
\nvided with Protractor) facilitate marking of angles as shown in figures 1A.4 and 1A.5.
\nThey are used to draw lines at 30
\n\u00b0
\n, 60
\n\u00b0
\nand 45
\n\u00b0
\nto the vertical and horizontal.
\nmm
\ng
\n. 1A.6. 45 Set Square with Protractor
\n0
\nd) Protractor:
\nProtractors are used to mark or measure angles between 0 and 180
\n\u00b0
\n. They are semicircular in shape
\n(of diameter 100mm) and are made of Plastic or celluloid which has more life. Protractors with circular shape
\ncapable of marking and measuring 0 to 360
\n\u00b0
\nare also available in the market.
\n180
\ne) Drawing Instrument Box :
\nIt consists of the following
\na) Large size compasses,
\nb) Large size divider,
\nc) Small size bow pen, bow divider, and
\nd) Lengthening bar
\nf) Drawing sheet:
\nThey are available in many varieties and good quality paper with smooth surface should be selected
\nfor Drawings which are to be preserved for longer time. Sizes of Drawing Sheets recommended by Bureau
\nof Indian Standards (B.I.S) is given below,
\nDrawing Instruments and their Uses
\n5
\nStandard size of Drawing sheet
\nDesignation
\nSize (mm)
\nDesignation
\nSize (mm)
\nA0
\n1189 \u00d7 841
\nA3
\n420 \u00d7 297
\nA1
\n841 \u00d7 594
\nA4
\n297 \u00d7 210
\nA2
\n594 \u00d7 420
\nA5
\n210 \u00d7 148
\ng) Drawing Pencils:
\nThe accuracy and appearance of a Drawing depends on the quality of Pencil used to make Draw-
\ning. The grade of a Pencil lead is marked on the Pencil. HB denotes medium grade. Increase in hardness
\nis shown by value put in front of H such as 2H, 3H etc., Softer pencils are marked as 2B, 3B, 4B etc. A
\nPencil marked 3B is softer than 2B and Pencil marked 4B is softer than 3B and so on. Beginning of a Draw-
\ning may be made with H or 2H. For lettering and dimensioning, H and HB Pencils are used.
\nh) Drawing Pins and clips:
\nThese are used to fix the Drawing sheet on the Drawing board.
\nCompass:
\nCompass is used for drawing circles and arcs of circles. The compass has two legs hinged at one
\nend. One of the legs has a pointed needle fitted at the lower end where as the other end has provision for
\ninserting pencil lead. Circles upto 120mm diameters are drawn by keeping the legs of compass straight. For
\ndrawing circles more than 150 mm radius, a lengthening bar is used. It is advisable to keep the needle end
\nabout 1mm long compared to that of pencil end so that while drawing circles, when the needle end is pressed
\nit goes inside the drawing sheet by a small distance (approximately 1mm).
\nassignment <\/p>\n
\u00a0Week 4; drawing instrument \u00a0 Technical pens More \u00a0 \u00a0 Drawing ink More \u00a0 \u00a0…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,61],"tags":[],"class_list":["post-299","post","type-post","status-publish","format-standard","hentry","category-posts","category-second-term-jss1-basic-technology"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/299","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/comments?post=299"}],"version-history":[{"count":1,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/299\/revisions"}],"predecessor-version":[{"id":300,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/299\/revisions\/300"}],"wp:attachment":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/media?parent=299"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/categories?post=299"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/tags?post=299"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}