CEST 51: Civil Drafting Technology Week 3 Lab Assignment Manual Drafting Lab Assignment 3: Basic Dimensioning (30 points) This lab assignment consists of two orthographic drawings (3A & 3B) that are to be fully dimensioned as described in the lecture slides, reading material, and as discussed in class. Use 1/8” tall hand lettering/numbering and 1/8" long arrowheads. Due to time constraints, I have already created the border, title block with guidelines, and the three orthographic views for each object. I have included an isometric view of each object in the upper right-hand corner to help you visualize the views better. Even though vellum is not being used for this assignment, it is still important to use a drafting board and the necessary tools. An architect's scale and an engineering scale will be required. The required scale is noted on each drawing. Be sure to hand letter your name, date, course #, and the title of the drawing "BASIC DIMENSIONING" in the title block spaces. Each correctly dimensioned drawing is worth 15 points. Rules to keep in mind: ● ● The drafter's primary concern when dimensioning an object is to convey the basic information needed to manufacture the part. It is critical that all necessary dimensions are shown. Part 1: Introduction to Basic Manual Drafting Santa Rosa Junior College All object dimensions are one of three types: Overall dimensions: provide the overall object size O Location dimensions: indicate where features lie along or within the object Size dimensions: specify how large the features are Location Size 1 Size Size Overall Location Location Size Overal T Location Dimension lines are drawn as a thin black line. It should be thin enough to contrast with the object lines. Dimension lines are usually broken near the center for the insertion of the actual hand lettered dimension value; however, placement of the lettered dimension may vary depending on space limitations. In order to avoid crowding, the dimension line should be placed at least 3/8" from the object and the spacing between dimension lines should be at least 1/4". Always be consistent with spacing distances. Manual Drafting Skills: Lab Assignment 3 - Page 1 of 2 CEST 51: Civil Drafting Technology Week 3 Lab Assignment ● FI+ ● 1 min. ကထ min. Dimension line does not extend past extension line Length of arrowhead Preferred Part 1: Introduction to Basic Manual Drafting Santa Rosa Junior College The dimension line should be "capped" at each end with arrowheads. Arrowheads are usually drawn 1/8" long with the height being approximately 1/3 of the length. It may seem easy enough but creating a proper hand drafted arrowhead takes a lot of practice. Dimension line Avoid For clarity, dimensions should confirm to the following rules: Place the location and size dimensions on the views that show the true shape of the feature being dimensioned (the primary view). Do not locate or give the size of features in secondary views. A secondary view is a view in which the feature is not visible. In most cases, dimensioning to a hidden line is not an acceptable practice. Always draw dimension lines parallel to the direction of measurement. If there are several parallel dimension lines, the numbers should be staggered to make them easier to read and to avoid crowding. Extension line - Extension line offset from object or object feature (max.) Dimensions should not be duplicated. Omit all unnecessary dimensions. ← Unless absolutely necessary, dimensions should not be placed within the object lines of the views. Instead, extension lines should be used to extend the dimensions to the outer perimeter of the object. If possible, dimensions should be grouped together rather than scattered about the drawing. When grouping, avoid extending extension lines more than halfway across any given view. If this is required, it is best to dimension the feature along the nearer side of the object. Dimensions must be complete. The person manufacturing the part should not have to assume any measurements or scale the drawing to make the part. D D 4 Manual Drafting Skills: Lab Assignment 3 - Page 2 of 2 Dimension the orthographic views below. The use of a straightedge and/or triangle is strongly recommended. Use 1/8" lettering. Follow the basic dimensioning rules as discussed in class. Use the proper scale to determine the dimensions. Round to the nearest 1 foot. SCALE: 1/2"=1'-0" 3A Dimension the orthographic views below. The use of a straightedge and/or triangle is strongly recommended. Use 1/8" lettering. Follow the basic dimensioning rules as discussed in class. Use the proper scale to determine the dimensions. Round to the nearest 1 foot. SCALE: 1" 30" 3B

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