PRECISION MEASURING EQUIPMENT

chucks. In general, the larger the drill (and motor), the slower the rpm, which provides the needed extra torque to twist a greater size drill bit. CAUTION Unplug the drill before attempting to tighten or remove drill bits. PORTABLE ELECTRIC OR NEUMATIC OPERATED SANDER The power sander (fig. 2-31) is one of the most desirable tools for scaling rust, removing paint, and smoothing decks and bulkheads before painting. The design of the portable power sander is much like that of the electric drill motor with the addition of the sanding disk attached at right angles. The average size disk sander used in the Navy is either 7 or 9 inches. PNEUMATIC CHIPPING HAMMER The pneumatic chipping hammer (fig. 2-32) is another tool useful to the ABF when scaling large areas in preparation for repainting. Air pressure sup- ply should be maintained to the manufacturer’s rec- ommended working pressures found on the nameplate attached to the tool. Never point the pneumatic chip- ping hammer at another person or yourself while air pressure is supplied to the tool. Personal injury could occur if the chisel was expelled at high speed from the scaling hammer. ROTARY IMPACT SCALER The rotary impact scaler (fig. 2-33) is a scaling and chipping tool, sometimes called a jitterbug. It is electric or pneumatic powered and has a bundle of cutters mounted on either side. In use, it is pushed along the surface to be scaled with the rotating chip- pers doing the work. Replacement bundles of cutters are available. NEEDLE IMPACT SCALER The needle impact scaler (fig. 2-34) has needlelike attachments that fit into one end. It is often called a needle-gun. This tool is used in conjunction with the rotary scaler and can clean out (scale) corners not reached by the other tool. PRECISION MEASURING EQUIPMENT LEARNING OBJECTIVES: Identify precision measuring equipment used by the ABF. Ex- plain the use and care of precision measuring equipment. As an ABF, you will be using measuring tools that read in the thousandths (0.001). On PMS and in major maintenance work, you will be required to use torque wrenches, micrometers, telescoping gages, vernier calipers, and dial indicators. Aligning pumps, check- ing shafts for wear, and checking bearings’ inside and outside diameters are just a few places where these tools are used. We will now go through the selection and use of the proper tool for the job at hand. TORQUE WRENCHES There are times when, for engineering reasons, a definite force must be applied to a nut or bolt head. In such cases a torque wrench must be used. For example, equal force must be applied to all the head bolts of an engine. Otherwise, one bolt may bear the brunt of the force of internal combustion and ultimately cause engine failure. The three most commonly used torque wrenches are the deflecting beam, dial indicating, and Figure 2-33.—Rotary impact scaler. 2-23 Figure 2-34.—Needle impact scaler (needle-gun).