- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2400) Unit Title: WOODWORKING ___________________________________________________________________________ (CLF2402) Topic: MEASURING & MARKING WOOD Time Year(s) 3 hours 1 / 2 / 3 / 4 ___________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the students will be able to: Learning Outcome #: (I-3) - Measure and mark wood for cutting and drilling. Special Material and Equipment: A measuring tape, combination square, carpenter's square, bevel square, level, chalk line, plumb line & bob, sharp pencil, and boards to be marked References: Cooper, Elmer L. (1987). AGRICULTURAL MECHANICS: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Jones, M. M. (1955). SHOPWORK ON THE FARM. New York: McGraw-Hill. Wagner, W. H. (1987). MODERN CARPENTRY. South Holland, IL: Goodheart Willcox. Evaluation: Quiz by instructor. TOPIC PRESENTATION: Measuring & Marking Wood A. Measuring and Marking Vocabulary 1. Straight - an adjective describing a line that is the shortest distance between two points 2. Square - an adjective describing lines, surfaces, or planes positioned at right angles (90 degrees) to one another 3. Perpendicular - an adjective describing a line, surface, or plane that is positioned at a right angle to another line, surface, or plane 4. Level - an adjective describing a line, surface, or plane lying parallel to the plane of the horizon (axis or the earth) having the same height everywhere 5. Plumb - an adjective describing a line, surface, or plane that is exactly vertical or true. 6. Flush - an adjective describing the positioning of two or more objects so that their edges, surfaces, or ends are even, level, or on the same plane 7. Bevel - a sloping edge (less than 90 degrees) 8. Miter - a term usually referring to a 45 degree angle 9. Working edge or surface - the main edge or surface from which the other surfaces are measured or squared A. Using a Tape Measure to Measure and Mark Wood: 1. Measuring the Distance between Two Points: a. Place the end of the tape precisely on the first point. 1) The hook on the end of most tapes slides a distance equal to the thickness of the hook in order to provide accurate measurements whether it is hooked onto the end or edge of a board or pushed against a surface. 2) If the hook is damaged or missing, start the measurement at the one inch graduation line and subtract one inch from tape reading. b. Extend the tape to the second point. 1) Make sure all slack is taken out of the tape between the two points, or the resulting reading will be too long. 2) Make sure the tape is flush with the edge of the board being measured. If the tape angles even slightly across the board, the reading will be too long. c. Read the tape at the graduation line on or nearest the second point (see lesson CLF2152 "Reading Measuring Tools"). 1) Long tapes are slightly arched across their width so they will remain fairly rigid while being extended; therefore, make sure the edge of the tape touches the wood if a very exact reading is required. 2) If measuring the distance between two inside surfaces, push the tape hook against one side and the tape case against the other, then read the graduation line nearest the tape case and add the length of the case to the reading. 2. Marking Wood for Cutting a. To lay off a measurement on a board, attach the tape hook to the end of the board or place the one inch graduation precisely at the beginning mark and mark the board with a sharpened pencil at the desired graduation line on the tape. 1) When laying off several measurements in a straight line along a board, do not raise or move the tape until all the measurements are marked. 2) If the tape is raised and moved for each measurement, the possibility of errors is greatly increased. b. To quickly and easily locate the middle of a board when the total width is a difficult-to-divide number (for example, 2 5/8" or 11 13/16"), lay a measuring tape across the board at any angle necessary to make full inch marks on the tape line up with both edges of the board. Then mark on the board the halfway point along the tape that is between the two edges of the board. 1) Do this at both ends of the board, then connect the two marks with the help of a straight edge or gauge. 2) This procedure can also be used to divide a board into three or more equal widths. B. Using Squares to Measure and Mark Wood 1. Using a Carpenter's Square (Framing Square) a. To mark boards to be sawed square (90 degrees to the working edge), use the following steps: 1) Measure and mark the desired length of the board. 2) Place the body of the square firmly against the working edge of the board. 3) Move the square until the inside edge of the tongue is against the length mark. 4) Holding a sharp pencil against the edge of the tongue, draw a thin line through the length mark and across the board. b. To mark boards to be sawed at the same angle, use the following steps: 1) Position the square with the outside edge of the tongue along the angle cut in the end of the board to be duplicated. 2) Record the readings where both the tongue and the body meet the edge of the board. 3) Position the square on the board to be marked with so that the same two readings meet the edge of the board. 4) Holding a sharp pencil against the edge of the tongue, draw a thin line across the board, which will be the same angle as the original board. 2. Using a Combination Square a. As a ruler, it can be used to measure distances up to 12 inches. b. As a straight edge, it can be used as a guide for marking straight lines between points. c. As a try square, it can be used for both marking and checking angles on wood. 1) It can be used as a guide to draw both 90 degree and 45 degree lines across the face, edge, or ends of boards. a) To mark a 90 degree angle, extend the blade from the 90 degree shoulder, and place that shoulder firmly against the working edge from which the other surfaces are to be measured or squared. b) To mark a 45 degree angle, extend the blade from the 45 degree shoulder, and place the shoulder firmly against the working edge. 2) It can be used to check the exactness of a right angle or miter angle cut by placing the appropriate shoulder firmly against the working edge and attempting to line up the blade with the cut. d. As a marking gauge, it can be used for marking lines parallel to the edge of a board. 1) Extend the blade the desired distance from the 90 degree shoulder. 2) Move the 90 degree shoulder along the edge while marking the wood with a pencil held against the end of the blade. e. As a depth gauge, it can be used to measure the depth of a dado or rabbet. f. As a level, it can be used to level or plumb an object. 3. Using the Sliding T-bevel Square a. It can be used to mark angles or bevels on wood. 1) The adjustable blade can be set to the desired angle by several methods. a) Place the handle against the working edge of the board and adjust the blade so that it fits the angle marked or cut across the board. b) Or, the angle can be set using a protractor if the degrees are known. 2) The bevel square set to the desired angle is then used as other squares are to mark off the angle. b. It can be used to check angles cut in wood. 1) Place the handle against the working edge of the board and adjust the blade so that it fits the angle cut across the board. 2) Place the handle against the base of a protractor and note the reading where the adjusted blade meets the arch. C. Using Chalk Lines, Plumb Lines, and Levels to Mark and Check Wood 1. Using a Chalk Line to Mark Wood a. Stretch a strong cotton or nylon string coated with colored chalk between the two points meant to be joined by a straight line. b. Lift the line midway between the two points and allow it to snap back into place. c. Remove the chalk line and a straight mark will be left. 2. Using a Plumb Line to Mark Wood a. It can be used to locate a point directly below another. 1) Tie the plumb line to a nail in the point desired and allow the plumb bob to come to rest. 2) Mark the wood directly below the point of the plumb bob. b. It can be used with a carpenter's square to mark a level line. 1) Suspend the plumb line and allow the plumb to come to rest. 2) Align the body of the square with the plumb line. 3) Mark the level line with a sharp pencil along the edge of the tongue of the square. 3. Using a Level to Mark Wood a. To make a level mark on a vertical surface, position the level against the surface so that the bubble in the middle tube is centered, then mark a line with a sharp pencil along the edge of the level. b. To make a plumb mark on a vertical surface, position the level against the surface so that the bubble in the tube located near the end of the level is centered, then mark a line with a sharp pencil along the edge of the level. _________________________________________________________ ACTIVITY: 1. Practice using a measuring tape to measure and mark wood for cutting. 2. Practice using squares to measure and mark wood for cutting. 3. Practice using a chalk line, plumb line, and level to mark wood for cutting. 4. Measure and mark wood to be cut for an ongoing wood project, such as a toolbox or sawhorse. _________________________________________________________ 6/20/91 OLR/tf #%&C