Teknologi Dan Rekayasa HAND TOOLS

LINE MARKERS Objective : After studying this unit, the student should be able to Identify and describe the various line markers Explain the difference between the prick punch and center punch Use the markers correctly

LINE MARKERS Marking tools must be able to scribe a line, circle, or arc permanently on a metal sheet so that the worker can follow it accurately with his cut. Prick punches and center punches are markers which permanently locate points, centers, and pattern outlines. Markers are made with hardened steel points for wearing quality and accuracy. Other marking devices, such as the soapstone and felt tipped pen, are used in installation work when marking is needed only for identification purposes.

THE SCRATCH AWL Scratch awl are available in lengths ranging from 5½ to 9 inches. Handles are made of wood, steel or plastic. The pointed blades are long and cylindrical, and measure from 1/8 to ¼ inches in diameter. They are heat treated to hold needle point. The points can be sharpened on a grinding wheel when necessary.

HOW TO USE A SCRATCH AWL 1. Hold the scratch awl as if holding a pencil 2. Mark the line location at two points on the metal surface 3. Place a straightedge on the location points 4. Draw a line with the scratch along the straightedge.

HOW TO USE A SCRATCH AWL

DIVIDER Dividers are available in 6, 8, and 10 inch lengths. They are adjusted to the desired dimension by a wingnut lock or screw. The points are heat treated steel to hold sharpness. Resharpening can done on the grinding wheel. Dividers are used for scribing circles or arcs as large as 48 inches in diameter. Other uses are line, arc, and circle division, and line transfer on a lay out.

THE TRAMMEL When circle or arcs larger than 48 inches must be scribed on a surface, a trammel is used. The trammel can be obtained with an adjustable sliding mechanism, and individual trammel points can be fastened to a rod of any desired length. center

HOW TO USE A DIVIDER OR TRAMMEL 1. Locate the center of the circle or arc on the stock 2. Indent the center with a prick punch or scratch awl. 3. Adjust the points of the dividers or trammel to the desired radius and secure 4. Place one point in the center location as a pivot 5. Rotate the other point by hand to scribe a circle

THE PRICK PUNCH The prick punch is made of tool steel which is hardened and drawn to hold a long, sharp, point. The conical point is ground to an included angle of 30 degrees like that of the scratch awl. The prick punch is very useful for transferring pattern on sheet metal surfaces and for punching hole centers.

HOW TO USE A PRICK PUNCH Scribe the points to be marked on the stock Hold the prick punch vertical to the stock surface with the point on the scribed location. Tap the head of the punch lightly with a hammer

THE CENTER PUNCH Center punch are very similar to the prick punch. They are also made of tool steel and are available in the same lengths and diameters as prick punches. The center punch differs only in respect to its point which is blunter than that of the prick punch and has an included angle of 90 degrees. The purposes of this tool are to mark hole centers and enlarge prick punch marks for drilling.

HOW TO USE A CENTER PUNCH Place the center punch so that it is vertical to the hole center location Tap the head of the punch sharply with a hammer. CAUTION : If the mark is made slightly off center, correct it by tipping the punch and hitting it towards the correct center.

USE A PRICK PUNCH AND CENTER PUNCH 60° 90°

USE A PRICK PUNCH AND CENTER PUNCH

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