How to Draft Machine Parts

Place the T-square on your drawing surface. The drawing surface should be flat, smooth and clean. Tape the paper or vellum to the drawing surface, parallel to the T-square. Divide the paper or vellum sheet into eight equal rectangles by drawing a line along the center of the length of the sheet and three lines along the center and quarter points of the long edge of the sheet. These eight equal rectangles define the drawing space for each orthogonal projection. If you do not have a sheet large enough for the eight drawings, use multiple drawing sheets.

Measure or determine the dimensions of each of the sides of the machine part. Many machine parts are drawn at real scale, where 1 inch equals 1 inch. However, parts larger than the drawing area must be scaled to accurately represent the whole form of the object. Determine the largest scale you can use to draw the part. Many standard scales include 1 inch equals 1 foot, 3 inches equals 1 foot, 6 inches equals 1 foot and 12 inches equals 1 foot, as well as 2:1, 3:1, 5:1 and 10:1, where the drawing is two, three, five or ten times larger than the actual part.

Draw the top, bottom, two sections and four sides of the machine part to scale in the eight boxes, using a pencil with the T-square, circle template and adjustable triangle. All dimensions and angles must be accurate and to scale. Use the circle template for arcs and circles of various diameters. The adjustable triangle, abutting the T-square, drafts any angle, including a 90-degree angle. Usually, the sides of a part are drawn relative to one another, where the front drawing is adjacent to both of the side drawings, etc.

Use an architectural or engineering scale to draw the part to scale. The fraction or number at either end of the architectural or engineering scale provides the scale, such as "1/2" at an end represents the side of the scale that is 1/2 inch equals 1 foot.

Annotate the drawings with text that describes drawing title, material, finish, surface texture, as well as the dimension strings to define the size of the machine part. Do not repeat annotations in each of the drawings-- if the height of the piece is dimensioned in one side view, do not repeat the dimension in another side view. Write the annotations 3/32-to-1/8 inch tall.

Provide a title block in the lower or upper right hand corner of the drawing, which provides the name of the part, associated machine or project, drawing scale, date and your name.