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Hand tools Metalworking
Woodworking Moretofollow |
The screwdriver is used to drive screws and to remove them. These are made in a variety of styles, such as the plain, ratchet, offset, and spiral. The screwdriver consists of a blade, the tip of which is shaped to fit the slot in the head of a screw, and a handle, which may be part of the blade, as in an offset screwdriver, or may be made of wood or some other material fastened to the blade by means of rivets.
Phillips screwdriver
The screwdriver tipThe choice of the correct tip to use when driving a screw is of the utmost importance. The tip should fit snugly in the screw slot and should not extend beyond the head. One that is too vide will extend beyond the head of the screw and star the wood as the screw is driven in.
Care of the screwdriverThe care of a screwdriver involves proper use of the tool. A screwdriver is designed to drive or re-move screws having slotted heads, and it should not be used for any other operation. If you use a screwdriver to pry open crates, to separate two pieces of wood, and so on, you are likely to bend the shank. This throws the tip out of center in relation to the handle, and the tool is then no longer safe to use as a screwdriver. The choice of the correct size tip to fit the slot of a particular screw is another factor in the care of the screwdriver. If the proper size of screwdriver is always used, the need for reconditioning the tip will be reduced considerably. While a screwdriver is not a keen-edged tool, the same protection should be given it as should be given a cutting tool. A screwdriver that is dropped or misused requires frequent reconditioning, which is wasteful of time and material. A screwdriver tip that does not have its proper shape should be put back in condition by grinding the blade. The tip of a screwdriver blade is first ground straight and square on the grindstone. The thickness of the tip at the end must be equivalent to the width of the slot in the screw that is to be driven. The flat surf aces on each side of the shank should be ground slightly concave so that they will be parallel at the end which fits into the screw slot. It is important to have the shape of these flat surfaces alike so that the tip will be on the center line of the shank. Use of the screwdriverWhen driving screws, the screw is generally placed in a hole which has been bored for it. The screwdriver is held with one hand over the end of the handle and the other hand on the stock with the thumb and first finger hooked around the blade to steady it. A downward pressure should be applied to the handle, twisting the hand at the wrist in a clockwise direction at the same time. The screwdriver must be held parallel to the vertical axis of the screw; it should never be tilted, for the tip may slide or jump out of the slot. After the screw has taken hold, the hand that was guiding the tip should be moved up and placed around the shank. This is a safety measure, for if the tip should slip out of the slot it might cut the hand. To remove screws, the same procedure should be followed except that the screwdriver is turned in a counterclockwise direction, and only enough pressure is used to hold the screwdriver in place. Safety with screwdriversThere are certain rules that must be observed by a person handling, using, or carrying a screwdriver to prevent injury to himself or damage to the work being assembled. A screwdriver tip should be of such shape and size as to fit the screw slot snugly. If such a screwdriver is not available, the one to be used should be shaped to fit. Failure to do this may result in damaging the screw slot to such an extent that the screw can be neither driven nor extracted. A screwdriver tip of the wrong shape and size may also cause the tool to slip out of the screw slot and damage the work or some vital piece of equipment near by. When the downward, twisting pressure is applied to a screwdriver, there is no way of controlling the screwdriver if it should slip out of the screw slot. When a screwdriver is used it must be kept in line with the axis of the screw and centered in the slot. Any shifting of the blade in its relation to the center of the head and the axis of the screw will result in its slipping out of the slot. A bent screwdriver blade cannot be kept in line with the axis of the screw and therefore should never be used. Although a screwdriver is not classed as a sharp cutting tool, it can do serious injury to a person if not used with the proper care. When using a screwdriver keep your hands behind the tip of the blade. It is a dangerous practice to place one hand behind the work to support it while the screwdriver is held and used in the other hand. If the screwdriver should slip it is very likely to do serious damage to the hand in front of it. Never carry a screwdriver in your pocket; if you should fall it is likely to stab you. Carry it in the tool box or in your hand with the tip down. Emergency substitutesAlthough whenever possible the correct tool should be used for every job, there may be times when a screwdriver, for example, is not to be had, yet a screw must be tightened or removed. A coin, a washer, the head of another screw, and such implements can be substituted for a screwdriver in an emergency.
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