Shears.
1. A cutting instrument, operating like scissors, but on a larger scale and somewhat differently shaped.
The edges of the blades are beveled, and the handles adapted for thumb and fingers respectively, instead of being duplicates.
They are adapted for tailors' use.
Shears with two blades and a spring back were used in old
Rome for clipping sheep, hair, and hedges.
Tinman's shears have relatively shorter jaws, and are either grasped in the hand or one leg placed in the vise while the other is worked by hand.
They
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are used for cutting tin-plate and sheet-metal of moderate thickness, such as stove-pipe plate.
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Mat-shearing machine. |
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Sheep-shearing table. |
Bench-shears have powerful blades with obtuse cuttingedges.
The handles are made long in proportion to the blades, and the end of the lower one is bent downwardly at right angles, so that it may be inserted into a hole in the work-bench or table.
Hand-shears are used between the thumb and finger, in the same manner as cloth-shears, but have a stronger edge, being intended for cutting sheet-metal.
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Shears for clipping animals. |
Fig. 4927 is a two-handed shears for clipping horses.
One handle is for holding it to place, and the other drives the circular cutter by means of a crank.
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Hand-shears. |
a, sheep-shears.
See also sheep-shears.
b, hand-shears or
snips, used by sheet-metal workers.
c, bench-shears, used by tinmen and others.
The blades are about one fifth of the total length, which is usually from 1 1/2 to 4 feet; the square tang is to be inserted in a hole in the work-bench or a heavy wooden block.
The handle is sometimes forged thicker at the end, to increase the cutting effect by its momentum when thrown down by a sudden jerk.
d, another form, in which the joint is at the extreme end, and the cutting-edge between it and the handle.
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Bench-shears. |
e, purchase-shears.
These are worked by a lever united by a connecting-rod to the movable blade, and considerably increasing the power; a spring is usually provided to press the two edges together, and a stop to determine the length or width of the pieces cut off. Were the edges of the blades not in contact, as seen at
g, the effect would be to fold rather than cut the metal, and strain the shears.
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Shears. |
f, shears and
squeezer. The lower piece is firmly fixed; the cutting-edges are near the joint; and dies may be placed in the far end for swaging hot pieces of metal.
The long arm of the cutting-lever is operated by a connectingrod and eccentric driven by the engine.
h, double shears, used at the
British Mint.
The lower
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piece has a cutter at each end, and acts by a rocking motion against the fixed upper piece.
i, bench-shears with a pivoted cutter, adjusted in each blade by means of a screw.
j. The blades are recessed at the pivot-hole
j′, so that the metal, in cutting, is not compressed so much at that point, in order that it may remain soft after hammering, allowing the rivet-holes to be readily punched.
k. Two short, strong blades are formed on the sides of the large ones for cutting wire, whalebone, etc.
k′. Cutting-nippers having cutters which are held by screws, so as to be removable and replaceable, are also used for this purpose.
Shears are also made having a thin cutting-blade closing in between two opposite blades, which serve as guides for the cutting-blade.
Another description is provided with a series of removable cutters of different sizes, having triangular cutting-faces; these are secured in one jaw and cut into a suitable slot in the opposite jaw.
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Shears. |
l. A stationary blade is fitted in the rabbeted face of the lower section, and a movable blade operated by a lever is hinged to the rabbeted face of the upper section; the faces of the sections give support to the blades.
m. For brush-makers.
The wedge-shaped throat in the lower stationary blade holds the bristles while they are severed by the downward movement of the upper blade.
n. For cutting the bloom or mill bar as it comes from the roughingrollers.
The cutting-edges of hard steel are bolted to the lower stationary frame and to the upper movable jaw, which is operated by a connecting-rod from the fly-wheel shaft of the engine.
The bar-shears have usually one stationary and one oscillating jaw, and are used to cut bars of iron into pieces to be built into fagots for reheating and rerolling to form beams, nail-plates, or some peculiar grades of iron which owe their quality to repeated working.
The moving jaw is operated by a cam on a rotating shaft, and makes its strokes in uniform time.
See bar-shear, page 241.
o. Metal-shears.
The cutters are attached and arranged as in the preceding case.
The long lever of the upper jaw is operated by an eccentric on the fly-wheel shaft pressing against a roller pivoted in the end of the lever.
The machine for cutting to a length angle-iron for ships' frames consists of a fixed cutter in the form of a right-angled triangular notch, in which the angle-iron to be cut is laid with the angle downward; the movable cutter is a solid right-angled triangle, with the right angle pointing downward; it is fixed in the lower end of a block which slides between vertical guides, and has a reciprocating motion given to it by an eccentric on a rotating shaft, making twenty revolutions per minute or thereabout.
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Hydraulic shears. |
The effort required to shear a piece of iron is about 50,000 pounds per square inch of the area of the shorn surface.
The work performed is about equal to that effort multiplied by half the thickness of the piece in the direction of shearing.
For an equal area of steel, the effort is probably about double.
The
shears for cutting plates for the outside skin of a ship consist of a pair of straight
cast-steel cutters; the lower one is fixed and horizontal; the upper or movable cutter has a slight slope to give it an oblique cut.
q r are forms of hydraulic shears.
The movable cutter is attached to the ram of a hydraulic press, making in the former a downward and in the latter an upward stroke.
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Shears and punch. |
Fig. 4933, a combined shears and punch.
The punch is connected with a lever making its effective stroke at one side of the machine, — the left in the illustration, — and operated by a yoke and a heartcam: the movable shear-blade is attached to a lever making its stroke at the other side, and operated by a yoke and eccentric.
The motions of both are derived from gearconnection with the fly-wheel
p.
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Circular-cutter shears. |
In
Fig. 4934, the circular cutters
e f are rotated in opposite directions by gears operated from the hand-wheel
g. A number of these cutters may be arranged on each shaft, so as to cut a sheet of metal into a series of strips.
2. The
ways or
track of a lathe upon which the lathehead, puppet-head, and rest are placed, and on which the latter is adjusted in the common lathe or slides in the traversing lathe.
3. For the hoisting device, see sheers.
See under the following heads:—
| Bar-shears. | Hydraulic shears. |
| Bench-shears. | Lopping-shears. |
| Button-hole shears. | Pruning-shears. |
| Cattle-marking shears. | Punch and shears. |
| Clipping-shears. | Scissors. |
| Cutting-nippers. | Shear-grinding machine. |
| Edging-shears. | Shearing-machine. |
| Garden-shears. | Shearing-table. |
| Grass-edging shears. | Sheep-shears. |
| Hair-clipping shears. | Sheet-metal shears. |
| Hand-shears. | Tailor's shears. |
| Hedging-shears. | Tinman's shears. |
