Marking and Measuring Tools
Marking in order to make wooden components of the required size or the marking of exact dimensions on the wooden piece is essential to produce quality jobs. A number of marking and measuring instruments namely Rules, Try Square, Combination Set, Bevel Gauge, Marking Gauge, Mortise Gauge, Cutting Gauge, Spirit Level, Trammel and Compass are commonly used for this purpose. Some of commonly used marking and measuring instruments are discussed as in chapter of fitting and sheet metal work under.
Rules are straight edge of wood or steel engraved in millimeters- centimeters or in inches-foot or in both. Theses are used to mark, measure the length, widths and thicknesses of wood part. Figs. 9.4.-9.6 show steel rule, folding rule and flexible steel rule. These rules are available in different sizes and designs. Metallic taps bearing sizes 6″, 12″ or 18″ are used for general measuring work. For example 24″ folding tape and 5″ or 6″ steel tape are used measuring larger dimensions. An important small instrument in any shop is a good quality straight-edge bench rules. These rules are manufactured of either metal or wood. They are used to check for straightness and to measure and mark straight lines. The bench rule may be graduated in inches, millimeters or both. The length of the bench rule may be 12″, 24″ or 36″. The 36″ rule is called yardstick. Another type of rule is folding two-foot rule which is more convenient than a straight 24″ rule. The zigzag rules are used to measure longer stock when exact measurements are not so important. One of These rules, when open may be of usually 6 or 8 feet long. The push pull steel tape or tape rule is a very compact metal rule that comes in lengths of 6, 8 or 10 feet. There is a hook at the end to slip over the edge of the bold. It is flexible to bends easily and can measure curved surfaces too. It is very good for measuring the inside depth of the hole of components also.
Try square is generally utilized for measuring and checking of squareness, perpendicularity, dimensions, testing of finish of planned surfaces and drawing parallel and perpendicular lines.
The steel blade and metallic or wooden handle of try square are at right angles to each other. Try square is used for testing the level, edge and square ness of the wooden surfaces. It is also used for marking lines across the face or edge of wooden block. There are graduations along the blade of the rule that are used for measuring and marking purposes on the wooden jobs. The blade of try square is made of hard tempered steel of non rusting kind. It is seldom used for hammering work.
Combination set is frequently used in the carpentry shop for different kind of measurements. It consists of blade and a head. The blade has a groove cut along its length so that it can slide into the head. One side of the head makes a 90° angle with the blade and the other side a 45° angle. It can be making, measuring and setting different angle. It also acts as a try square, angle gauge to set 45° angles, a depth gauge and level checking tool.
Bevel gauge is also known as an adjustable bevel which is mainly used for marking, measuring and inspecting angles from 0 to 180 degree. Its blade can be adjusted and set to any desired angle.
The marking gauge is made of wood which is important tool utilized to make lines at a uniform distance from the edge of a board or piece of work and is used principally when preparing wooden components to size before jointing. The marking gauge like the mortise gauge and cutting gauge in use should be positioned correctly. For marking purposes, the gauge is drawn towards the body or pushed away from it but in either case, if the spur does not trail. It will tend to jump and run with the grain. Thumb screw of the marking gauge locks the stock at any position. The spur made of hardened steel should be ground to a fine point. And for ease of working, it should not project too far from the face of the stem. It is commonly used to mark or scribe line parallel to and at any desired distance from a finished edge or face of a surface.
Cutting gauge is similar in construction to the marking gauge but having a knife in place of the marking pin or spur. It can be utilized for gauging and marking deep lines across the grain of wood in thicker sections. It is also used for setting out the shoulder-lines of lap dovetails and similar joints, as well as for trimming veneers parallel to the edge of surface before laying a cross-band. Cross banding is the laying of a strip of cross-grained veneer around the edge of a surface for example the edges of a table top, box lid or drawer front. This gauge is very useful for making very small rebates to receive inlay lines and may be used in place of marking gauge. Inlay lines are thin strips of wood which can be glued into a rebate cut around the edge of a veneered surface.
9.7 shows a mortise gauge. This is an improved form of marking gauge which consists of main components as fixed pin, sliding pin, brass strip, stem, rose wood stock and thumb screw. The fixed pin of the gauge is attached to a short brass strip which is screwed to the stem. The sliding pin is fixed to a long brass strip or slider is adjusted by means of a thumbscrew. The threaded portion of which engages in a cylindrical nut which is embedded in the stem. The stock is locked in position by a metal set screw. This gauge is used for marking out of the parallel sides of a mortises or tenons and other similar joints.
Holding And Supporting Tools
Sometimes it is desirable to support and gold a wooden board in a special manner while the work is being carried out. For these purposes, various supporting and holding devices are needed some of which are discussed as under.
Every carpenter generally needs a good solid bench or table of rigid construction of hard wood on which he can perform or carry out the carpentry operations. Work bench should be equipped with a vice for holding the work and with slots and holes for keeping the common hand tools. One jaw of the vice is tightened to the table and is kept moveable for holding the articles Work benches are built solidly with good heavy tops for providing a good working surface for cutting, as well. The vice on the bench is equipped with an adjustable dog that is, a piece of wood or metal can be moved up and down in the outside jaw of the vice.
Carpenter vice (Fig. 9.
Clamps are commonly used in pairs in gluing up operations at the final assembly of wood joinery work. These clamps can provide pressure required to hold joints together until they are secured due to the setting of glues. Clamps are of two types namely plain rectangular bar type and T-bar type. The former is made of mild steel and is usually rectangular in section. The later may be of T-section, which can easily afford greater rigidity under stress. The coarse adjustment jaw may be located in any position on the bar by means of a steel pin which fits into any of the holes drilled at intervals along the bar. The fine adjustment jaw of the sash clamp is moved along the bar by a square threads screw which passes through a special nut fixed to the end of bar. Considerable pressure can be applied by turning the screw with the Tommy bar for holding a wooden job. Both jaws of the sash clamp are generally made of malleable cast iron which is tougher and less brittle than ordinary cast iron. There are other similar types of such clamps named as rack clamp, screw clamps, light duty parallel clamp, adjustable bar clamp (Fig. 9.9), G or C-clamp (Fig. 9.10), and double bar clamp which are useful for holding different sizes and shapes of wooden jobs.
Various kinds of cutting tools namely various kinds of saws, planes, chisels, scraper, files, and rasp adze and axe and boring tools such as brace and bits, bradawl, auger, gimlet are used in the carpentry shop. Few important types of cutting tools are described as under.
Saws are wood cutting tools having handle and a thin steel blade with small sharp teeth along the edge. They are utilized to cut wood to different sizes and shapes used for making the wooden joints that hold parts together. They can be further classified into three major types namely hand Saws (Rip, Cross-cut, Panel, Keyhole and, Pad saw), Snuff Saws (Tenon and Dovetail) and Frame Saws (Coping, Bow and Fret). Few important types of saws are shown in Fig. 9.11. Some of them are described as under.
The rip saw is shown in Fig. 9.11. It is used for cutting timber along the grains. The teeth of rip saw are chisel-shaped and are set alternately to the right and left. A 24″ long point saw is a good for sawing work. Depending upon whether the saw is designed to rip or cross-cut, the shape of the teeth will also vary. In the case of a ripsaw, the teeth are shaped like chisels.
Cross cut saw is shown in Fig. 9.11 which is similar to rip saw in shape. It is primarily designed for cutting across the grains of wood. The teeth are knife shaped and bent alternately to the right and left for making the saw to cut wider than the blade. The saw cut is called the kerf. Since the kerf is wider than the blade, the blade will not stick as the sawing is done. The saw teeth may be coarse (with only 4 or 5 teeth per inch) or fine (with ten or twelve teeth per inch). A jaw for general purpose cutting should have about eight or nine points per inch (there is one more point than teeth per inch) and should be about 24 inches long.
The turning saw is similar to the copying saw which is designed for cutting curves, scrolls and roundings on wooden jobs. It is used chiefly on heavier work where long fast stroke and less accuracy of cutting are required. The thin blade of the turning saw is removable. This saw can be pivoted between the handles. The saw generally cuts in the pulling stroke.
Dovetail saw is shown in Fig. 9.11 which is little and is closely similar as related to the backsaw or tennon saw. It is lighter and however possesses a thinner blade and finer teeth. The handle is round, to provide a delicate grip for fine cutting. This saw is used where absolutely finer and delicate cutting is required in wood work.
Compass saw carries a tapered blade which is long as shown in Fig. 9.11 which is one of the special saw having thin, narrow and flexible blade. With a blade resembling the beak of a swordfish, this type of saw is commonly used for making cutouts on the inside surface of a piece of work. A hole is first bored inside the portion which is to be cut out and the pointed compass saw is pushed into the hole to start the sawing operation. Its blade contains about 12 teeth per cm length
The keyhole saw is used in the same manner as the compass saw. For this reason it is generally employed for fine internal and intricate work where the compass saw would be too big and clumsy for the carpentry job.
Hacksaw is shown in Fig. 9.12 which consists of steel frame and a hacksaw blade. While essentially designed for cutting metal, this tool comes in for a variety of uses in the wood working shop. The frame of hacksaw is designed in different ways, some with pistol grips, others with handles similar to those used on a conventional saw and others with turned handles. Blades of hacksaw are detachable and can be obtained with teeth of varying coarseness.