 |
| |
 |
|
|
|||||
|
Hand tools Metalworking
Woodworking |
The hand drillThe hand drill is very outdated, but some still use them. It is used to bore holes in wood. The hand drill is used with drills or bits having a round tang. The tang is the end of the bit by means of which it is held in the brace. The maximum chuck opening determines the size of a hand drill. Because it is getting rare, some pictures of older drawing tools.
The hand drill is held by the handle with one hand, and the other hand is placed on the crank. The angle at which the drill is to enter the wood and make the hole is controlled by the hand which is holding the handle. This hand applies the downward pressure and must therefore be kept steady to prevent breaking the drill. The crank should be turned at a constant speed in a clockwise direction. When the hole has been drilled to the desired depth, the drill is removed from the hole by continuing the turning of the crank in a clockwise direction and drawing the drill out by the handle. Under no conditions should the rotation of the crank be reversed while drilling a hole. If that is done, the chuck may open and the drill come out. The material being drilled must be held securely in a vise or by some other means. If any attempt is made to drill holes in wood or metal which is not being held securely, the drill is likely to break. The bit brace
When placing a bit in the brace, the bit must be centered in the chuck and locked in place. The jaws of the chuck are opened by revolving the shell in a counterclockwise direction. They should be opened just far enough to set the corners of the tang in the V-grooves of the jaws. With the bit standing up in the jaws, the shell is turned so as to open the jaws more. As the jaws open, the bit will slide down. This is continued until the bit takes a sudden drop. The bit is now in place, and by reversing the rotation of the shell the jaws can be closed around the shank. A bit put into a chuck in this manner will be centered and cannot fall out. The gimlet bitThe gimlet bit is used for boring small holes for screws and nails. The gimlet bit makes a hole by actually removing wood. The function of the point is to center the bit on the hole location and to start the cutting of the wood. The outer edge of the spiral is sharpened to do the cutting. The wood chips, as they are produced by the action of the cutting edge, collect in the flute and are carried up and out of the hole as the bit is revolved.
The twist bitThe twist bit is used to bore holes in wood for screws, nails, and bolts. The twist bit should not be confused with the twist drill, although they look similar. The twist bit has a steeper cutting angle than a twist drill. The twist bit can be used for boring holes in wood only; but the twist drill can be used on both wood and metal.
Twist bits are made in sizes ranging from 1/16”to 5/8”, with gradations of 1/32”. The size of the bit is measured across the widest part of the bit and is indicated on the tang by means of a number. A #8 twist bit will bore a hole 8/32" in diameter. The auger bitThe auger bit is more often used by the woodworker to bore holes than any other type of bit. It consists of four main parts: the cutting end, the twist, the shank, and the tang. The cutting end consists of a feed screw, which draws the bit into the wood as it is turned; the spurs, which cut the fibers around the edge of the hole; and the lips, which follow the spurs and cut out the wood. The twist carries the chips, made by the cutting end, up out of the hole.
The Foerstner bitThe Foerstner bit is similar in action and use to the auger bit, differing in appearance only to the extent that there is no feed screw or centering point. It is used to bore holes in thin stock where there would be danger of splitting the wood with the feed screw if an auger bit were used. It is also used to bore holes part-way through, where if the auger bit were used the feed screw or spurs would go through the wood. The Foerstner bit contains all the essential parts of an auger bit except the feed screw. The spurs are in the form of semicircular rims. The lips extend from the rim to the center. The slit in the side of the rim allows the wood chips to pass from the cutting edge of the bit up through the hole that is being bored. On the smaller sizes of Foerstner bits the shank has a spiraled groove or twist to provide a means for removing the wood chips from the hole. The sizes of the Foerstner bit range from 1/4" up, graduated in sixteenths of an inch. They are measured from spur to spur, with the bit size indicated by a number stamped on the tang. A #4 would indicate a bit that will bore a hole 4/16” in diameter. In order to center a Foerstner bit, a circle the size of the hole must be scribed with dividers. The rim of the Foerstner bit is then pressed into this circle. The expansive bitThe expansive bit is an auger bit which is used to bore holes from7/8" to 3". The bit comes supplied with two cutters which make it possible to bore any size hole within this range. The smaller cutter is used to bore holes from 7/8" to 1 3/4", and the larger cutter is used to bore holes from 1 3/4" to 3". The various parts of the expansive bit are identical in name and function with those of the auger bit. The clamp and clamp screw are used to hold the adjustable cutters in place. The cutters of the expansive bit have marked along the lower edge graduations indicating the diameter of the hole that the bit will bore. On the clamp is a reference mark for setting the cutter. The clamp screw is loosened with a screwdriver, by turning the screw in a counterclockwise direction. When doing this, place the bit on the bench top rather than hold it in your hand. After the screw is loosened, thereby releasing the pressure of the clamp on the cutter, the cutter can be slid in either direction for setting. The graduations on the cutter indicating the diameter of the hole in inches and fractions of an inch must be brought in line with the reference mark on the clamp. The screw is tightened after the cutter has been set. The countersinkThe countersink is a bit used to taper screw holes so that the head of a flathead screw will set flush with the surface of the wood or slightly below the surface. The cutter is shaped at an angle equivalent to the slant or taper of the underside of a flat-head screw. Countersinks come in sizes of 1/2", 5/8", and 3/4", the size indicating the greatest diameter of the cutter. The depth to which a screw hole should be countersunk will depend on the diameter of the screw head and the distance below the surface of the wood that the screw is to be set. The twist drillThe twist drill is primarily a metalworking drill, but it can be used for wood. These drills come in a greater range of sizes than can be obtained in the regular woodworking bits and are extremely useful when boring small holes.
Metal-drilling bits
Using a bit brace and bit
The brad awlThe brad awl is a tool resembling a small screwdriver. It is used to start holes which are to be made by an auger or expansive bit. It is also used to make small holes for screws and nails. The brad awl consists of a steel blade, tapered on opposite sides to produce a sharp edge, and set into a handle. The handle is equipped with a ferrule to prevent it from splitting. Brad awls come in sizes ranging from 5/65” to 1/8", the measurement indicating the width of the tip. When using a brad awl the tip should be placed at the intersection of the lines which locate the hole; the edge of the blade should extend across the grain. If the edge of the awl is run with the grain, the wood is likely to split. The brad awl should be held at right angles to the stock, and pressed downward into the wood. The tip is driven into the piece of wood and held there; then the brad awl is revolved one-quarter of a turn and taken out. When making deep holes for screws or nails, the brad awl is revolved several times chile the downward pressure is maintained. Sharpening bits and drillsTwist bits and twist drills are sharpened on a grindstone. There are three angles at the cutting end of the bit and drill that must be watched: the lip angle, the lip-clearance angle, and the clearance angle in back of the cutting lip. When grinding a twist drill or bit, the lip angle must be identical on each side and the length of the lips must be equal. Any difference in angle will result in only one lip's doing the cutting. If the lengths are not equal, the bit or drill will bore an oversize hole. When grinding, hold the bit or drill against the face of the stone at the angle of the lip. Revolve it slightly until the lip angle has been ground, taking care not to grind away the lip. Auger bits, Foerstner bits, and expansive bits, being similar in form, are all sharpened in the same manner. A special type of file, known as the auger-bit file, is used. This particular file is double-ended; one end has teeth cut on the faces of the file and the edges uncut, and at the other end the teeth are on the edges with the faces clear. A file of this type permits the sharpening of the spurs without damaging the lip. The spur of an auger bit must be sharpened on the inside only. The outside of the spur should never be touched with a file, for this would reduce the diameter of the cutting end of the bit and make it impossible to bore a hole. The lip is sharpened on the top to maintain the clearance of the cutting edge. Drill pressesThe sensitive drillA commonly used type of drill press is a sensitive drill because pressure is applied to the drill by a lever held in the hand of the operator. The operator learns by experience just how much pressure to apply to insure the most efficient operation of the drill. The sensitive drill is widely used for light work employing the smaller sized drills. In the illustration, the piece held in the vise is being drilled. This vise is specially made for use on a drill-press table. It is so made that its sides are parallel, which makes the vise useful in holding work while drilling holes at right angles to a surface. The power-fed drill pressWhen heavy drilling is done, a power-fed drill press is used. In this drill press, power is used to feed the drill into the work. This is done by a series of gears which are driven from the shaft which drives the drill. In the sensitive drill, the operator determines the rate at which the drill is fed into the work by the amount of pressure he applies. In the power-fed drill the rate at which the drill advances into the work is determined by meshed gears in the driving mechanism. The operator may bring different gears into mesh by using levers, much as in shifting the gears of an automobile. In heavy drilling, work must always be strapped to the table of the drill press or held securely by some other means. If the work moves out of line it may be ruined, and someone may be injured. Careless use of a drill press is indicated when holes have been drilled through the table. In shops where skillful and careful mechanics are employed, drill presses are used for years without this happening. |
