1. POWER TOOLS
Learning Objective: Upon completing this section, you should be able to determine the proper use and maintenance requirements of portable power tools.
Your duties as a builder include developing and improving your skills and techniques when working with different power tools. In this section, we’ll identify and discuss the most common power tools that are in the builder’s workshop or used on the jobsite. We’ll also discuss safety precautions as they relate to the particular power tool under discussion. You must keep in mind and continually stress to your crew that woodworking power tools can be dangerous, and that safety is everyone’s responsibility.
As a builder, you might be assigned to a shop. Therefore, you will need to know some of the common power tools and equipment found there.
Shop Radial Arm Saw
Figure 3-1 illustrates a typical shop radial arm saw. The procedures used in the operation, maintenance, and lubrication of any shop radial arm saw are found in the manufacturers’ operator and maintenance manuals. The safety precautions to be observed for this saw are found in these same manuals. The primary difference between this saw and other saws of this type (field saws) is the location of controls.
Tilt-Arbor Table Bench Saw
A tilt-arbor table bench saw (figure 3-2) is so named because the saw blade can be tilted for cutting bevels by tilting the arbor. The arbor, located beneath the table, is controlled by the tilt handwheel. In earlier types of bench saws, the saw blade remained stationary and the table was tilted. A canted (tilted) saw table is hazardous in many ways; most modern table saws are of the tilt-arbor type.
To rip stock, remove the cutoff gauges and set the rip fence away from the saw by a distance equal to the desired width of the piece to be ripped off. The piece is placed with one edge against the fence and fed through with the fence as a guide.
To cut stock square, set the cutoff gauge at 90° to the line of the saw and set the ripping fence to the outside edge of the table, away from the stock to be cut. The piece is then placed with one edge against the cutoff gauge, held firmly, and fed through by pushing the gauge along its slot.
Figure 3-1.—A shop radial arm saw.
Figure 3-2.—Tilt-arbor bench saw.
The procedure for cutting stock at an angle other than 90° (called miter cutting) is similar, except that the cutoff gauge is set to bring the piece to the desired angle with the line of the saw.
For ordinary ripping or cutting, the saw blade should extend above the table top 1/8 to 1/4 inch plus the thickness of the piece to be sawed. The vertical position of the saw is controlled by the depth of cut handwheel, shown in figure 3-2. The angle of the saw blade is controlled by the tilt handwheel. Except when its removal is absolutely unavoidable, the guard must be kept in place.
The slot in the table through which the saw blade extends is called the throat. The throat is contained in a small, removable section of the table called the throat plate. The throat plate is removed when it is necessary to insert a wrench to remove the saw blade.
The blade is held on the arbor by the arbor nut. A saw is usually equipped with several throat plates, containing throats of various widths. A wider throat is required when a dado head is used on the saw. A dado head consists of two outside grooving saws (which are much like combination saws) and as many intermediate chisel-type cutters (called chippers) as are required to make up the designated width of the groove or dado. Grooving saws are usually I/S-inch thick; consequently, one grooving saw will cut a 1/8-inch groove, and the two, used together, will cut a 1/4-inch groove. Intermediate cutters come in various thicknesses.
Observe the following safety precautions when operating the tilt-arbor table bench saw:
- Do not use a ripsaw blade for crosscutting or a crosscut saw blade for ripping. When ripping and crosscutting frequently, you should install a combination blade to eliminate constantly changing the blade. Make sure the saw blade is sharp, unbroken, and free from cracks before using. The blade should be changed if it becomes dull, cracked, chipped, or warped.
- Be sure the saw blade is set at proper height above the table to cut through the wood.
- Avoid the hazard of being hit by materials caused by kickbacks by standing to one side of the saw.
- Always use a push stick to push short, narrow pieces between the saw blade and the gauge.
- Keep stock and scraps from accumulating on the saw table and in the immediate working area.
- Never reach over the saw to obtain material from the other side.
- When cutting, do not feed wood into the saw blade faster than it will cut freely and cleanly.
- Never leave the saw unattended with the power on.
Although the band saw (figure 3-3) is designed primarily for making curved cuts, it can also be used for straight cutting. Unlike the circular saw, the band saw is frequently used for freehand cutting.
The band saw has two large wheels on which a continuous narrow saw blade, or band, turns, just as a belt is turned on pulleys. The lower wheel, located below the working table, is connected to the motor directly or by means of pulleys or gears and serves as the driver pulley. The upper wheel is the driven pulley.
The saw blade is guided and kept in line by two sets of blade guides, one fixed set below the table and one set above with a vertical sliding adjustment. The alignment of the blade is adjusted by a mechanism on the backside of the upper wheel. Tensioning of the blade—tightening and loosening-is provided by another adjustment located just back of the upper wheel.
Cutoff gauges and ripping fences are sometimes provided for use with band saws, but you’ll do most of your work freehand with the table clear. With this type of saw, it is difficult to make accurate cuts when gauges or fences are used.
The size of a band saw is designated by the diameter of the wheels. Common sizes are 14-, 16-, 18-, 20-, 30-, 36-, 42-, and 48-inch-diameter wheel machines. The 14-inch size is the smallest practical band saw. With the exception of capacity, all band saws are much the same with regard to maintenance, operation, and adjustment.
Figure 3-3.—Band saw.
A rule of thumb used by many Seabees is that the width of the blade should be one-eighth the minimum radius to be cut. Therefore, if the piece on hand has a 4-inch radius, the operator should select a 1/2-inch blade. Don’t construe this to mean that the minimum radius that can be cut is eight times the width of the blade; rather, the ratio indicates the practical limit for high-speed band saw work.
Blades, or bands, for band saws are designated by points (tooth points per inch), thickness (gauge), and width. The required length of a blade is found by adding the circumference of one wheel to twice the distance between the wheel centers. Length can vary within a limit of twice the tension adjustment range.
Band saw teeth are shaped like the teeth in a hand ripsaw blade, which means that their fronts are filed at 90° to the line of the saw. Reconditioning procedures are the same as those for a hand ripsaw, except that very narrow band saws with very small teeth must usually be set and sharpened by special machines.
Observe the following safety precautions when operating a band saw:
- Keep your fingers away from the moving blade.
- Keep the table clear of stock and scraps so your work will not catch as you push it along.
- Keep the upper guide just above the work, not excessively high.
- Don’t use cracked blades. If a blade develops a click as it passes through the work, the operator should shut off the power because the click is a danger signal that the blade is cracked and may be ready to break. After the saw blade has stopped moving, it should be replaced with one in proper condition.
- If the saw blade breaks, the operator should shut off the power immediately and not attempt to remove any part of the saw blade until the machine is completely stopped.
- If the work binds or pinches on the blade, the operator should never attempt to back the work away from the blade while the saw is in motion since this may break the blade. The operator should always see that the blade is working freely through the cut.
- A band saw should not be operated in a location where the temperature is below 45°F. The blade may break from the coldness.
- Using a small saw blade for large work or forcing a wide saw on a small radius is bad practice. The saw blade should, in all cases, be as wide as the nature of the work will permit.
- Band saws should not be stopped by thrusting a piece of wood against the cutting edge or side of the band saw blade immediately after the power has been shut off; doing so may cause the blade to break. Band saws with 36-inch-wheel diameters and larger should have a hand or foot brake.
- Particular care should be taken when sharpening or brazing a band saw blade to ensure the blade is not overheated and the brazed joints are thoroughly united and finished to the same thickness as the rest of the blade. It is recommended that all band saw blades be butt welded where possible; this method is much superior to the old style of brazing.
Figure 3-4 shows a drill press. (The numbers in the figure correspond to those in the following text.) The drill press is an electrically operated power machine that was originally designed as a metal-working tool; as such, its use would be limited in the average woodworking shop. However, accessories, such as a router bit or shaper heads, jigs, and special techniques, now make it a versatile woodworking tool as well.
Figure 3-4.—Drill press.
The motor (10) is mounted to a bracket at the rear of the head assembly (1) and designed to permit V-belt changing for desired spindle speed without removing the motor from its mounting bracket. Four spindle speeds are obtained by locating the V-belt on any one of the four steps of the spindle-driven and motor-driven pulleys. The belt tensioning rod (16) keeps proper tension on the belt so it doesn’t slip.
The controls of all drill presses are similar. The terms “right” and “left” are relative to the operator’s position standing in front of and facing the drill press. “Forward” applies to movement toward the operator. “Rearward” applies to movement away from the operator.
The on/off switch (11) is located in the front of the drill press for easy access.
The spindle and quill feed handles (2) radiate from the spindle and quill pinion feed (3) hub, which is located on the lower right-front side of the head assembly (1). Pulling forward and down on any one of the three spindle and quill feed handles, which point upward at the time, moves the spindle and quill assembly downward. Release the feed handle (2) and the spindle and quill assembly return to the retracted or upper position by spring action.
The quill lock handle (4) is located at the lower left-front side of the head assembly. Turn the quill lock handle clockwise to lock the quill at a desired operating position. Release the quill by turning the quill lock handle counterclockwise. However, in most cases, the quill lock handle will be in the released position.
The head lock handle (5) is located at the left-rear side of the head assembly. Turn the head leek handle clockwise to lock the head assembly at a desired vertical height on the bench column. Turn the head lock handle counterclockwise to release the head assembly. When operating the drill press, you must ensure that the head lock handle is tight at all times.
The head support collar handle (6) is located at the right side of the head support collar and below the head assembly. The handle locks the head support collar, which secures the head vertically on the bench column, and prevents the head from dropping when the head lock handle is released. Turn the head support collar lock handle clockwise to lock the support to the bench column and counterclockwise to release the support. When operating the drill press, ensure that the head support collar lock handle is tight at all times.
As you face the drill press, the tilting table lock handle is located at the right-rear side of the tilting table bracket. The lockpin secures the table at a horizontal or 45° angle. This allows you to move the table to the side, out of the way for long pieces of wood. The table support collar (8) allows you to raise or lower the table. Turn the tilting table lock handle counterclockwise to release the tilting table bracket so it can be moved up and down or around the bench column. Lock the tilting table assembly at the desired height by turning the lock handle clockwise. When operating the drill press, ensure that the tilting table lock handle is tight at all times.
The adjustable locknut (14) is located on the depth gauge rod (17). The purpose of the adjustable locknut is to regulate depth drilling. Turn the adjustable locknut clockwise to decrease the downward travel of the spindle. The locknut must be secured against the depth pointer (13) when operating the drill press. The depth of the hole is shown on the depth scale (15).
Observe the following safety precautions when operating a drill press:
- Make sure that the drill is properly secured in the chuck (12) and that the chuck key (9) is removed before starting the drill press.
- Make sure your material is properly secured.
- Operate the feed handle with a slow, steady pressure to make sure you don’t break the drill bit or cause the V-belt to slip.
- Make sure all locking handles are tight and that the V-belt is not slipping.
- Make sure the electric cord is securely connected and in good shape.
- Make sure you are not wearing hanging or loose clothing.
- Listen for any sounds that may be signs of trouble.
- After you have finished operating the drill press, make sure the area is clean.
The woodworking lathe is, without question, the oldest of all woodworking machines. In its early form, it consisted of two holding centers with the suspended stock being rotated by an endless rope belt. It was operated by having one person pull on the rope hand over hand while the cutting was done by a second person holding crude hand lathe tools on an improvised beam rest.
The actual operations of woodturning performed on a modern lathe are still done to a great degree with woodturner’s hand tools. However, machine lathe work is coming more and more into use with the introduction of newly designed lathes for that purpose.
The lathe is used in turning or shaping round drums, disks, and any object that requires a true diameter. The size of a lathe is determined by the maximum diameter of the work it can swing over its bed. There are various sizes and types of wood lathes, ranging from very small sizes for delicate work to large surface or bull lathes that can swing jobs 15 feet in diameter.
Figure 3-5 illustrates a type of lathe that you may find in your shop. It is made in three sizes to swing 16-, 20-, and 24-inch diameter stock. The lathe has four major parts: bed, headstock, tailstock, and tool rest.
The lathe shown in figure 3-5 has an iron bed and comes in assorted lengths. The bed is a broad, flat surface that supports the other parts of the machine.
The headstock is mounted on the left end of the lathe bed. All power for the lathe is transmitted through the headstock. It has a fully enclosed motor that gives variable spindle speed. The spindle is threaded at the front end to receive the faceplates. A faceplate attachment to the motor spindle is furnished to hold or mount small jobs having large diameters. There is also a flange on the rear end of the spindle to receive large faceplates, which are held securely by four stud bolts.
The tailstock is located on the right end of the lathe and is movable along the length of the bed. It supports one end of the work while the other end is being turned by the headstock spur. The tail center can be removed from the stock by simply backing the screw. The shank is tapered to center the point automatically.
Figure 3-5.—A woodworking lathe with accessories.
Most large sizes of lathes are provided with a power-feeding carriage. A cone-pulley belt arrangement provides power from the motor, and trackways are cast to the inside of the bed for sliding the carriage back and forth. All machines have a metal bar that can be attached to the bed of the lathe between the operator and the work. This serves as a hand tool rest and provides support for the operatorin guiding tools along the work. It may be of any size and is adjustable to any desired position.
In lathe work, wood is rotated against the special cutting tools (illustrated in figure 3-6). These tools include turning gouges (view A); skew chisels (view B); parting tools (view C); round-nose (view D); square-nose (view E); and spear-point (view F) chisels. Other cutting tools are toothing irons and auxiliary aids, such as calipers, dividers, and templates.
Figure 3-6.—Lathe cutting tools.
Turning gouges are used chiefly to rough out nearly all shapes in spindle turning. The gouge sizes vary from 1/8 to 2 or more inches, with 1/4-, 3/4-, and 1-inch sizes being most common.
Skew chisels are used for smoothing cuts to finish a surface, turning beads, trimming ends or shoulders, and for making V-cuts. They are made in sizes from 1/8 to 2 1/2 inches in width and in right-handed and left-handed pairs.
Parting tools are used to cut recesses or grooves with straight sides and a flat bottom, and also to cut off finished work from the faceplate. These tools are available in sizes ranging from 1/8 to 3/4 inch.
Scraping tools of various shapes are used for the most accurate turning work, especially for most faceplate turning. A few of the more common] y used shapes are illustrated in views D, E, and F of figure 3-6. The chisels shown in views B, E, and F are actually old jointer blades that have been ground to the required shape; the wood handles for these homemade chisels are not shown in the illustration.
A toothing iron (figure 3-7) is basically a square-nose turning chisel with a series of parallel grooves cut into the top surface of the iron. These turning tools we used for rough turning of segment work mounted on the face plate. The points of the toothing iron created by the parallel grooves serve as a series of spear point chisels (detail A); therefore, the tool is not likely to catch and dig into the work like a square-nose turning chisel. The toothing iron is made with course, medium, and fine parallel grooves and varies from 1/2 to 2 inches in width.
Figure 3-7.—Toothing iron lathe tool.
- Lathe turning can be extremely dangerous. You therefore must use particular care in this work. Observe the following safety precautions:
- When starting the lathe motor, stand to one side. This helps you avoid the hazard of flying debris in the event of defective material.
- The tool rest must be used when milling stock.
- Adjust and set the compound or tool rest for the start of the cut before turning the switch on.
- Take very light cuts, especially when using hand tools.
- Never attempt to use calipers on interrupted surfaces while the work is in motion.
The jointer is a machine for power planing stock on faces, edges, and ends. The planing is done by a revolving butterhead equipped with two or more knives, as shown in figure 3-8. Tightening the set screws forces the throat piece against the knife for holding the knife in position. Loosening the set screws releases the knife for removal. The size of a jointer is designated by the width, in inches, of the butterhead; sizes range from 4 to 36 inches. A 6-inch jointer is shown in figure 3-9.
The principle on which the jointer functions is illustrated in figure 3-10. The table consists of two parts on either side of the butterhead. The stock is started on the infeed table and fed past the butterhead onto the outfeed table. The surface of the outfeed table must be exactly level with the highest point reached by the knife edges. The surface of the infeed table is depressed below the surface of the outfeed table an amount equal to the desired depth of cut. The usual depth of cut is about 1/16 to 1/8 inch.
Figure 3-8.—Four-knife butterhead for a jointer.
Figure 3-9.—Six-inch jointer.
Figure 3-10.—Operating principle of a jointer.
The level of the outfeed table must be frequently checked to ensure the surface is exactly even with the highest point reached by the knife edges. If the outfeed table is too high, the cut will become progressively more shallow as the piece is fed through. If the outfeed table is too low, the piece will drop downward as its end leaves the infeed table, and the cut for the last inch or so will be too deep.
To set the outfeed table to the correct height, first feed a piece of waste stock past the cutterhead until a few inches of it lie on the outfeed table. Then, stop the machine and look under the outfeed end of the piece. If the outfeed table is too low, there will be a space between the surface of the table and the lower face of the piece. Raise the outfeed table until this space is eliminated. If no space appears, lower the outfeed table until a space does appear. Now, run the stock back through the machine. If there is still a space, raise the table just enough to eliminate it.
Note that the cutterhead cuts toward the infeed table; therefore, to cut with the grain, you must place the piece with the grain running toward the infeed table. A piece is edged by feeding it through on edge with one of the facesheld against the fence. A piece is surfaced by feeding it through flat with one of the edges against the fence. However, this operation should, if possible, be limited to straightening the face of the stock. The fence can be set at 90° to produce squared faces and edges, or at any desired angle to produce beveled edges or ends.
Only sharp and evenly balanced knives should be used in a jointer cutting head. The knives must not be set to take too heavy a cut because a kickback is almost certain to result, especially if there is a knot or change of grain in the stock. The knives must be securely refastened after the machine has been standing in a cold building over the weekend.
Each hand-fed jointer should be equipped with a cylindrical cutting head, the throat of which should not exceed 7/1 6 inch in depth or 5/8 inch in width. It is strongly recommended that no cylinder be used in which the throat exceeds 3/8 inch in depth or 1/2 inch in width.
Each hand-fed jointer should have an automatic guard that covers all the sections of the head on the working side of the fence or gauge. The guard should automatically adjust horizontally for edge jointing and vertically for surface work, and it should remain in contact with the material at all times.
When operating the jointer, observe the following safety precautions:
- Always plane with the grain. A piece of wood planed against the grain on a jointer may be kicked back.
- Never place your hands directly over the inner cutterhead. Should the piece of wood kick back, your hands will drop on the blades. Start with your hands on the infeed bed. When the piece of wood is halfway through, reach around with your left hand and steady the piece of wood on the outfeed bed. Finish with both your hands on the outfeed bed.
- Never feed a piece of wood with your thumb or finger against the end of the piece of wood being fed into the jointer. Keep your hands on top of the wood at all times.
- Avoid jointing short pieces of wood whenever possible. Joint a longer piece of wood and then cut it to the desired size. If you must joint a piece of wood shorter than 18 inches, use a push stick to feed it through the jointer.
- Never use a jointer with dull cutter blades. Dull blades have a tendency to kick the piece, and a kickback is always dangerous.
- Keep the jointer table and the floor around the jointer clear of scraps, chips, and shavings. Always stop the jointer before brushing off and cleaning up those scraps, chips, and shavings.
- Never joint a piece of wood that contains loose knots.
- Keep your eyes and undivided attention on the jointer as you are working. Do not talk to anyone while operating the jointer.
Remember, the jointer is one of the most dangerous machines in the woodworking shop. Only experienced and responsible personnel should be allowed to operate it using the basic safety precautions provided above.
A single surfacer (also called a single planer) is shown in figure 3-11. This machine surfaces stock on one face (the upper face) only. (Double surfacers, which surface both faces at the same time, are used only in large planing mills.)
Figure 3-11.—Single surfacer.
The single surfacer cuts with a cutterhead like the one on the jointer, but, on the single surfacer, the cutterhead is located above instead of below the drive rollers. The part adjacent to the cutterhead is pressed down against the feed bed by the chip breakers (just ahead of the cutterhead) and the pressure bar (just behind the cutterhead). The pressure bar temporarily straightens out any warp a piece may have; a piece that goes into the surfacer warped will come out still warped. This is not a defect in the machine; the surfacer is designed for surfacing only, not for truing warped stock. If true plane surfaces are desired, one face of the stock (the face that goes down in the surfacer) must be trued on the jointer before the piece is feed through the surfacer. If the face that goes down in the surfacer is true, the surfacer will plane the other face true.
Observe the following safety precautions when operating a surfacer:
- The cutting head should be covered by metal guards.
- Feed rolls should be guarded by a hood or a semicylindrical guard.
- Never force wood through the machine.
- If a piece of wood gets stuck, turn off the surfacer and lower the feed bed.
The shaper is designed primarily for edging curved stock and for cutting ornamental edges, as on moldings. It can also be used for rabbeting, grooving, fluting, and beading.
The flat cutter on a shaper is mounted on a vertical spindle and held in place by a hexagonal spindle nut. A grooved collar is placed below and above the cutter to receive the edges of the knives. Ball bearing collars are available for use as guides on irregular work where the fence is not used. The part of the edge that is to remain uncut runs against a ball bearing collar underneath the cutter, as shown in the bottom view of figure 3-12. A three-wing cutter (top view of figure 3-12) fits over the spindle. Cutters come with cutting edges in a great variety of shapes.
Figure 3-12.—Three-wing cutter for a shaper. fence.
For shaping the side edges on a rectangular piece, a light-duty shaper has an adjustable fence, like the one shown on the shaper in figure 3-13. For shaping the end edges on a rectangular piece, a machine of this type has a sliding fence similar to the cutoff gauge on a circular saw. The sliding fence slides in the groove shown in the table top.
Figure 3-13.—Light-duty shaper with adjustable
On larger machines, the fence consists of a board straightedge, clamped to the table with a hand screw, as shown in figure 3-14. A semicircular opening is sawed in the edge of the straightedge to accommodate the spindle and the cutters. Whenever possible, a guard of the type shown in the figure should be placed over the spindle.
Figure 3-14.—Shaper table showing straightedge fence and guard
For shaping curved edges, there are usually a couple of holes in the table, one on either side of the spindle, in which vertical starter pins can be inserted. When a curved edge is being shaped, the piece is guided by and steadied against the starter pin and the ball bearing collar on the spindle.
When operating a shaper, observe the following safety precautions:
- Like the jointer and surfacer, the shaper cuts toward the infeed side of the spindle, which is against the rotation of the spindle. Therefore, stock should be placed with the grain running toward the infeed side.
- Make sure the cutters are sharp and well secured.
- If curved or irregularly shaped edges are to be shaped, place the stock in position and make sure the collar will rub against the part of the edge, which should not be removed.
- Whenever the straight fence cannot be used, always use a starting pin in the table top.
- Never make extremely deep cuts.
- Make sure the shaper cutters rotate toward the work.
- Whenever possible, always use a guard, pressure bar, hold-down, or holding jig.
- If possible, place the cutter on the shaper spindle so that the cutting will be done on the lower side of the stock.
- Do not attempt to shape small pieces of wood.
- Check all adjustments before turning on the power.
The spindle shaper is one of the most dangerous machines used in the shop. Use extreme caution at all times.
PORTABLE HAND TOOLS
In addition to using power shop tools, you will be required to operate different types of portable hand tools in the field. You therefore need to understand the safety precautions associated with these.
Portable Electric Circular Saw
Figure 3-15.-Side-drive (view A) and worm-drive (view B) circular saws
The portable electric circular saw is used chiefly as a great labor-saving device in sawing wood framing members on the job. The size of a circular saw is determined by the diameter of the largest blade it can use. The most commonly used circular saws are the 7 1/4- and 8 1/4-inch saws. There are two different types of electric saws, as shown in figure 3-15: the side-drive (view A) and the worm-drive (view B). Circular saws can use many different types of cutting blades, some of which are shown in figure 3-16.
Figure 3-17 shows how versatile the circular saw can be.
Figure 3-16.-Circular saw blades.
Figure 3-17.-Different ways to use a circular saw.
COMBINATION CROSSCUT AND RIP BLADES.— Combination blades are all-purpose blades for cutting thick and thin hardwoods and softwoods, both with or across the grain. They can also be used to cut plywood and hardboard.
CROSSCUT BLADES.— Crosscut blades have fine teeth that cut smoothly across the grain of both hardwood and softwood. These blades can be used for plywood, veneers, and hardboard.
RIP BLADES.— Rip blades have bigger teeth than combination blades, and should be used only to cut with the grain. A rip fence or guide will help you make an accurate cut with this type of blade.
HOLLOW-GROUND BLADES.— Hollow-ground blades have no set. They make the smoothest cuts on thick or thin stock. Wood cut with these blades requires little or no sanding.
ABRASIVE BLADES.— Abrasive blades are used for cutting metal, masonry, and plastics. These blades are particularly useful for scoring bricks so they can be easily split.
To make an accurate ripping cut (Fig. 3-17, view A), the ripping guide is set a distance away from the saw equal to the width of the strip to be ripped off. It is then placed against the edge of the piece as a guide for the saw. To make a bevel angle cut up to 45° ((Fig. 3-17, view B), you just set the bevel adjustment knob to the angle you want and cut down the line. To make a pocket cut ((Fig. 3-17, views C and D), a square cut in the middle of a piece of material, you retract the guard back and tilt the saw so that it rests on the front of the base. Then, lowering the rear of the saw into the material, hold it there until it goes all the way through the wood. Then, follow your line.
Observe the following safety precautions when operating a circular saw:
- Don’t force the saw through heavy cutting stock. If you do, you may overload the motor and damage it.
- Before using the saw, carefully examine the material to be cut and free it of nails or other metal objects. Cutting into or through knots should be avoided, if possible.
- Disconnect the saw from its power source before making any adjustments or repairs to the saw. This includes changing the blade.
- Make sure all circular saws are equipped with guards that automatically y adjust themselves to the work when in use so that none of the teeth protrude above the work. Adjust the guard over the blade so that it slides out of its recess and covers the blade to the depth of the teeth when you lift the saw off the work.
- Wear goggles or face shields while using the saw and while cleaning up debris afterward.
- Grasp the saw with both hands and hold it firmly against the work. Take care to prevent the saw from breaking away from the work and thereby causing injury.
- Inspect the blade at frequent intervals and always after it has locked, pinched, or burned the work. Disconnect the saw from the power source before performing this inspection.
- Inspect daily the electric cords that you use for cuts or breaks. Before cutting boards, make sure the cord is not in the way of the blade.
The saber saw (figure 3-18) is a power-driven jigsaw that cuts smooth and decorative curves in wood and light metal. Most saber saws are light-duty machines and not designed for extremely fast cutting.
Figure 3-18.-Saber saw.
There are several different, easily interchangeable blades (figure 3-19) designed to operate in the saber saw. Some blades are designed for cutting wood and some for cutting metal.
The best way to learn how to handle this type of tool is to use it. Before trying to do a finished job with the saber saw, clamp down a piece of scrap plywood and draw some curved as well as straight lines to follow. You will develop your own way of
Figure 3-19.-Saber saw blades.
gripping the tool, which will be affected somewhat by the particular tool you are using. On some tools, for example, you will find guiding easier if you apply some downward pressure on the tool as you move it forward. If you don’t use a firm grip, the tool will tend to vibrate excessively and roughen the cut. Do not force the cutting faster than the design of the blade allows or you will break the blade.
You can make a pocket cut with a saber saw just like you can with a circular saw, although you need to drill a starter hole to begin work. A saber saw can also make bevel-angle and curve cuts.
Observe the following safety precautions when operating the saber saw:
- Before working with the saber saw, be sure to remove your rings, watches, bracelets, and other jewelry.
- If you are wearing long sleeves, roll them up. Be sure the saber saw is properly grounded.
- Use the proper saw blade for the work to be done, and ensure the blade is securely locked in place.
- Be sure the material to be cut is free of any obstructions.
- Keep your full attention focused on the work being performed.
- Grip the handle of the saw firmly. Control the forward and turning movements with your free hand on the front guide.
- To start a cut, place the forward edge of the saw base on the edge of the material being worked, start the motor, and move the blade into the material.
Portable Reciprocating Saw
The portable reciprocating saw (saw-all) (figure 3-20) is a heavy-duty power tool that you can use for a variety of woodworking maintenance work, remodeling, and roughing-in jobs. You can use it to cut rectangular openings, curved openings, along straight or curved lines, and flush.
Blades for reciprocating saws are made in a great variety of sizes and shapes. They vary in length from 2 1/2 to 12 inches and are made of high-speed steel or carbon steel. They have cutting edges similar to those shown in figure 3-19.
Figure 3-20.-Reciprocating saw.
Before operating this saw, be sure you are using a blade that is right for the job. The manufacturer’s instruction manual shows the proper saw blade to use for a particular material. The blade must be pushed securely into the opening provided. Rock it slightly to ensure a correct fit, then tighten the setscrew.
To start a cut, place the saw blade near the material to be cut. Then, start the motor and move the blade into the material. Keep the cutting pressure constant, but do not overload the saw motor. Never reach underneath the material being cut.
Observe the following safety precautions when operating a reciprocating saw:
- Disconnect the saw when changing blades or making adjustments.
- Place the foot of the saw firmly on the stock before starting to cut.
- Don’t cut curves shaper than the blade can handle.
- When cutting through a wall, make sure you don’t cut electrical wires.
The router is a versatile portable power tool that can be used free hand or with jigs and attachments. Figure 3-21 shows a router typical of most models. It consists of a motor containing a chuck into which the router bits are attached. The motor slides into the base in a vertical position. By means of the depth adjustment ring, easy regulation of the depth of a cut is possible. Routers vary in size from 1/4 to 2 1/2 horsepower, and the motor speed varies from 18,000 to 27,000 rpm.
Figure 3-21.-Portable router with edge guide.
One of the most practical accessories for the router is the edge guide. It is used to guide the router in a straight line along the edge of the board. The edge guide is particularly useful for cutting grooves on long pieces of lumber. The two rods on the edge
guide slip into the two holes provided on the router base. The edge guide can be adjusted to move in or out along the two rods to obtain the desired lateral depth cut.
Figure 3-22.-Router bits.
There are two classifications of router bits. Built-in, shank-type bits fit into the chuck of the router. Screw-type bits have a threaded hole through the center of the cutting head, which allows the cutting head to be screwed to the shank. Figure 3-22 shows a few of the most common router bits.
- Observe the following safety precautions when operating a router:
- Before operating a router, be sure the work piece is well secured and free of obstruction.
- Make sure the router is disconnected from the power source before making any adjustment or changing bits.
- Don’t overload the router when cutting the material.
- Use both hands to hold the router when cutting material.
Portable Power Plane
The portable electric power plane (figure 3-23) is widely used for trimming panels, doors, frames, and so forth. It is a precision tool capable of exact depth of cut up to 3/16 inch on some of the heavier models. However, the maximum safe depth of cut on any model is 3/32 inch in any one pass.
Figure 3-23.-Portable electric power plane.
The power plane is essentially a high-speed motor that drives a cutter bar, containing either straight or spiral blades, at high speed.
Operating the power plane is simply a matter of setting the depth of cut and passing the plane over the work. First, make careful measurements of the piece, where it is to fit, and determine how much material has to be removed. Then, the stock being planed should be held in a vise, clamped to the edge of a bench, or otherwise firmly held. Check the smoothness and straightness of all the edges.
If a smoothing cut is desired, make that cut first and then recheck the dimensions. Make as many passes as necessary with the plane to reach the desired dimensions, checking frequently so as not to remove too much material. The greater the depth of the cut, the slower you must feed the tool into the work. Feed pressure should be enough to keep the tool cutting, but not so much as to slow it down excessively. Keep wood chips off the work because they can mar the surface of the stock as the tool passes over them. Keep your hands away from the butterhead or blades when a cut is finished.
The L-shaped base, or fence, of the plane should be pressed snugly against the work when planing, assuring that the edge will be cut square. For bevel cuts, loosen the setscrew on the base, set the base at the desired bevel, and then retighten the setscrew.
- Observe the following safety precautions when operating a portable power plane:
- Make sure that the plane is turned off before plugging it in.
- Make sure you disconnect the plug before making any adjustment.
- Don’t attempt to power plane with one hand—you need two.
- Always clamp your work securely in the best position to perform the planing.
- When finished planing, make sure you disconnect the power cord.
Portable Power Drills
Portable power drills have generally replaced hand tools for drilling holes because they are faster and more accurate. With variable-speed controls and special clutch-drive chucks, they can also be used as electric screwdrivers. More specialized power-driven screwdrivers are also available; these have greatly increased the efficiency of many fastening operations in construction work.
The two basic designs for portable electric drills (figure 3-24) are the spade design for heavy-duty construction (view A) and the pistol-grip design for lighter work (view B). Sizes of power drills are based on the diameter of the largest drill shank that will fit into the chuck of the drill.
Figure 3-24.-Heavyduty 1/2-inch portable drill (view A) and light-duty 1/2-inch portable drill (view B).
The right-angle drill is a specialty drill used in plumbing and electrical work. It allows you to drill holes at a right angle to the drill body.
Observe the following safety precautions when operating a portable drill:
- Make sure that the drill or bit is securely mounted in the chuck.
- Hold the drill firmly as prescribed by the manufacturer of the drill.
- When feeding the drill into the material, vary the pressure you apply to accommodate the different kinds of stock. Be careful not to bind the drill or bit.
- When drilling a deep hole, withdraw the drill several times to clean the drill bit.
There are three types of portable sanders: belt, disk, and finish sanders. When using a belt sander (figure 3-25), be careful not to gouge the wood. The size of a belt sander is usually identified by the width of its sanding belt. Belt widths on heavier dutymodels are usually 3 or 4 inches. Depending on the make and model, belt lengths vary from 21 to 27 inches. Different grades of-abrasives are available.
Figure 3-25.-Belt sander.
Figure 3-26.-Portable disk sander.
The disk sander (figure 3-26) is a useful tool for removing old finish, paint, and varnish from siding, wood flooring, and concrete. For best results with a disk sander, tip the machine lightly with just enough pressure to bend the disk. Use a long, sweeping motion, back and forth, advancing along the surface. When using a disk sander, always operate it with both hands.
The finish sander (figure 3-27) is used for light and fine sanding. Two kinds of finish sanders are available. One operates with an orbital (circular) motion (view A), and the other has an oscillating (back and forth) movement (view B). Finish sanders use regular abrasive paper (sandpaper) cut to size from full sheets.
Figure 3-27.-Two types of finish sanders: orbital (view A) and oscillating (view B).
Observe the following safety tips when operating portable sanders:
- Make sure the sander is switched off before plugging it in.
- Make sure that you use two hands if using the belt sander.
- Don’t press down on the sander. The weight of the sander is enough to sand the material.
- Make sure the sander is disconnected when changing sandpaper.
- Keep the electrical cord away from the area being sanded.
Power Nailers and Staplers
There is a wide variety of power nailers and staplers available. A typical example of each is shown in figure 3-28. A heavy-duty nailer is used for framing or sheathing work; finish nailers are used for paneling or trimming. There is also a wide variety of staplers that you can use for jobs, such as fastening sheeting, decking, or roofing. These tools are often driven by compressed air. The amount of pneumatic, or air, pressure required to operate the tool depends on the size of the tool and the type of operation you are performing. Check the manufacturer’s manual for the proper air pressure to operate the tool.
Figure 3-28.-Heavyduty pneumatic nailer (view A) and pneumatic stapler (view B).
The power nailer and power stapler are great timesaving tools, but they are also very dangerous tools. Observe the following safety precautions when using them:
When you are not using a nailer or stapler or if you are loading one, disconnect the air supply.
- Use the correct air pressure for the particular tool and job.
- Use the right nailer or stapler for the job and also the correct nails and staples.
- Keep the nose of the tool pointed away from your body.