Boring tools

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Try square usage

The word boring means one thing to the woodworker and another to the machinist. To the woodworker, boring a hole means using an auger to make a hole in a piece of wood. To a machinist boring means enlarging and truing up a hole which has already been made.

Another word which conveys different meanings is the word drill. The woodworker calls the tool which penetrates the wood a bit or a drill bit and the device which holds and turns it a drill or hand drill and brace. The machinist calls the tool that penetrates the metal a drill.

The tool that drives the drill may be a breast drill, a hand drill, a drill press, a sensitive drill, or an electric drill, but to a machinist the driven tool is always a drill.

The hand drill

The hand drill is very outdated, but some still use them.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.

Hand drill To open a chuck to receive a drill, the shell is held in one hand and the crank is turned in a counterclockwise direction. The jaws of the chuck should be opened only slightly more than is necessary to insert the drill. After the drill is placed in the chuck, the shell is held tightly in one hand while the crank is turned in a clockwise direction.

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

Bit brace

The bit brace is a tool used, when boring a hole, to hold a bit or drill with a square tapered tang. There are two types of bit braces, the plain brace and the ratchet brace. The ratchet permits the handle of a brace to be turned in the opposite direction with out moving the bit. The ratchet collar controls the ratchet action.

Bit braces come in various sizes, the most common of which are 6", 8", 10", and 12". The size of the brace is determined by the sweep — the diameter of the arc made by the handle as it is revolved. Braces having a small sweep should be used with small bits.

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 bit

The 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.

Gimlet bit Gimlet bits are made in sizes ranging from 1/16" to 3/8", with gradations of 1/32". The size of the bit is measured across the widest part of the spiral. A number stamped on the tang indicates the size of the bit. A #4 bit will bore a hole 1/32" in diameter.

The twist bit

The 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 bit The twist bit is made of steel. Its cutting end is ground to a point; and a spiraled flute extends from the point upward along the shank. The end of the shank is a tang by which the bit is held in the brace.

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 bit

The 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.

Auger bit Auger bits range in sizes from 3/16" up, with gradations of 1/16. They are measured from spur to spur. The bit size is stamped on the tang, the number indicating the width of the bit in sixteenths of an inch. A #7 bit will bore a hole “7/16" in diameter.

The Foerstner bit

The 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 bit

The 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 countersink

The 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 drill

The 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.

Twist drill Twist drills are marked for size by means of numbers, letters, or fractions. The numbers range from 1 to 80; #1 drill will bore a hole .2280" in diameter (approximately 15/64") and #80 drill will bore a hole .0135" in diameter (a little smaller than 1/64"). The letter-marked drills run from A to Z; the A drill is .234" in diameter (15/64) and the Z drill is .413" in diameter (a little less than 27/64"). Twist drills marked in fractions of an inch range from 1/64" upward, in gradations of 1/64".

Metal-drilling bits

Metal drilling bits Shown two types of drills are shown; each has special advantages. For iron and steel the twist drill gives satisfactory service. The spiral flute causes the chips to rise to the top of the hole and so prevents choking. In drilling in soft metals, the twist drill has a tendency to screw itself into the material much as a wood screw does in wood. When a drill does this it is said to "hog in," and drill breakage is likely to result. To avoid this difficulty the straight flute drill is used in drilling the softer metals.

Using a bit brace and bit

Using a bit brace and bit

The stock into which a hole is to be bored must be held securely in a vise or held to the bench by means of a clamp. The brace is held with one hand on the head and the other hand on the handle.

The hand that is placed on the head controls the angle at which the bit is to enter the wood; that hand must keep the brace steady. The handle of the brace is turned in a clockwise direction to bore the hole, and turned in the opposite direction to remove the bit from the wood.

When boring holes through a piece of wood with an auger bit or an expansive bit it is desirable to bore from both sides.

If bored through from one side only, the stock should be backed up with a piece of scrap wood in order to prevent splitting the wood when the bit breaks through.

The brad awl

The 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 drills

Twist 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 presses

The sensitive drill

A 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 press

When 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.