Presentation on theme: "Unit 14 Portable Power Saws"— Presentation transcript:
1 Unit 14 Portable Power Saws Power Tool Safety • Circular Saws • Reciprocating Saws • Jigsaws • Cutout Saws • Chain Saws
2 A portable GFCI compares the amount of current in the hot or ungrounded conductor with the amount of current in the common or grounded conductor and immediately breaks the circuit if a difference greater than 5 mA exists.Per OSHA 29 CFR , Wiring Design and Pro-tection, all electric corded tools, equipment, or devices must use either ground fault circuit interrupter (GFCI) outlets or acceptable means of grounding to ensure worker safety. A GFCI protects against electrical shock by detecting an imbalance of current in the normal conductor pathway and then quickly opening the circuit (in as little as 1/40 of a second). The most common type of GFCI outlet used on a job site is a portable GFCI. See Figure Portable GFCIs should be inspected and tested before each use. GFCIs have a built-in test circuit to ensure that the ground fault protection is operational.
3 Various configurations of approved grounded outlets are available for construction power tools and equipment.If GFCIs are not available, an acceptable means of grounding must be established to prevent shock. In order to be grounded, a power tool must have a three-conductor cord with a three-prong plug that fits into a grounded outlet. See Figure 14-2.
4 In a typical grounding system, a ground wire runs from the power tool (in this case, a circular saw) to the grounded plug. Another ground wire runs from the grounded receptacle to a grounding bar in the service panel. A copper ground wire extends from the service panel to a ground rod or other grounding means in the earth.A grounded outlet has a ground wire that is connected to a water pipe or a ground rod driven into the earth. If a fault occurs in the tool, the electrical current travels through the ground wire in the cord and then to the ground wire connected to the outlet. Figure 14-3 shows a typical grounding system.
5 Side-drive and worm-drive circular saws are frequently used in construction work. Two types of circular saws are used in construction—side-drive and worm-drive saws. See Figure 14-4.
6 Blade diameter affects the maximum depth of cut Blade diameter affects the maximum depth of cut. When the blade angle is set to 45°, the depth of cut is decreased.The size of a circular saw is based on the largest diameter blade that can be properly installed. Circular saw blade diameters range from 4 1/2″ to 12″, with 7 1/4″, 7 1/2″, or 8 1/4″ diameter blades commonly used by carpenters. Figure 14-5 lists the different sizes of blades that are available and the depths to which they can cut at 45° or 90° angles.
7 Different blades are used with a circular saw for different operations. Many types of blades are used with circular saws. The proper circular saw blade to use for an application is based on the material being cut and the grain direction in which the cut is being made. See Figure Rip blades have teeth shaped for cutting in the direction of the grain. Rip blades should not be used for plywood. Crosscut blades are used to cut across the grain and can be used to cut plywood. Combination blades are used for both crosscut and ripping operations. Combination blades are used more often than rip or crosscut blades since most jobs require sawing with and across the grain. Combination blades produce a rough cut.
8 When cutting a compound angle with a circular saw, set the depth of the blade slightly more than the thickness of the material.When cutting a piece of material with a circular saw, set the blade so the blade gullets clear the wood. The depth of the cut is adjusted by raising or lowering the blade in relation to the saw base. The blade is locked into place with a lever or knob. When adjusting the blade to cut at an angle, loosen the bevel-adjustment knob, or tilt knob or lever, to tilt the base to the desired angle of the cut. See Figure The knob or lever is then retightened.
9 When crosscutting long boards supported by sawhorses, do not cut between the sawhorses. Instead, make a cut past the end of a sawhorse.When crosscutting long pieces, support the material with sawhorses. See Figure Position the material with the waste piece overhanging the sawhorse. Do not make cuts between sawhorses; this causes the saw to bind and kick back.
10 Position the panel to be cut with the waste piece overhanging the supporting panels. Plywood panels are supported by sawhorses or by other panels. When using sawhorses to support plywood panels, some carpenters place 2″ boards beneath the panels to prevent the cut pieces from dropping down and binding the saw. When using other panels for support, position the panel to be cut with the waste piece overhanging the supporting panels. See Figure 14-9.
11 An adjustable fence attachment aids in making a narrow rip cut with a circular saw. Most circular saws can accommodate a fence attach-ment to make an accurate narrow rip cut. In Figure , a fence attachment is used to guide a circular saw along the bottom of a door when trimming it to size.
12 A straightedge aids in making a straight cut across a panel. To make an accurate cut for a wider piece, tack down a straightedge as shown in Figure
13 Stand to one side of a circular saw during use. Circular saws are equipped with a constant pressure switch or control that shuts off the power when the pressure is released. A circular saw must be properly grounded or double-insulated to ensure carpenter safety. Safety rules to observe when using a circular saw include the following:• Wear appropriate eye protection such as safety glasses or goggles.• Verify the retractable guard is operational before using a circular saw.• Wait until the blade stops rotating before removing the saw from the material after completing a cut.• Stand to one side of a circular saw in case of kickbacks. See Figure• Always disconnect the electrical plug before changing blades or making adjustments.• Remove all damaged or cracked saw blades from service.
14 A reciprocating saw is used for a variety of applications such as cutting a door jamb or notching a stud.A reciprocating saw is a multipurpose cutting tool in which the blade reciprocates (quickly moves back and forth) to create the cutting action. A reciprocating saw is particularly useful for remodeling work where sections of framing members, sheathing, or inside wall covering must be cut out. See Figure
15 Different blades are used with a reciprocating saw to cut different materials. Many different blades are available for cutting different materials and for various types of cutting operations. Shapes of some of the more common blades are shown in Figure In general, the more teeth per inch, the smoother the cut. Fewer teeth per inch result in a rougher, but quicker cut.
16 A jigsaw is used to saw along curved lines and to cut circular and rectangular openings. A jigsaw, or saber saw, is a portable power saw used to cut thin wood and nonwood products. See Figure
17 The jigsaw cuts with an orbital movement The jigsaw cuts with an orbital movement. The blade cuts on the upstroke and moves slightly away from the material on the downstroke.The narrow blade of a jigsaw extends from the base and cuts with an orbital (circular) movement. The blade cuts on the upstroke and moves slightly away from the material on the downstroke. See Figure
18 A cutout saw uses a spiral bit to cut openings in wood and nonwood materials such as an opening in gypsum board for a receptacle box.A cutout saw, or spiral-cut saw, uses a 1/8″ or 1/4″ bit to cut through wood and nonwood materials up to 1″ thick. See Figure While especially useful for cutting openings in gypsum board, a cutout saw can also be used to cut laminate countertop sink cutouts, cement and backer board, and other materials. The tip of the bit is slowly plunged into the material until the base rests against the surface. The bit is then guided either free-hand or against a surface such as the interior edges of a receptacle box.
19 A chain saw is used to cut heavy timbers and pilings. A chain saw is used to cut heavy timbers and pilings and is useful equipment on demolition projects. See Figure Chain saws are electrically or gasoline powered. Gasoline-powered chain saws are typically more pow-erful and easily used in remote locations.