(fig. 2-3) is required. This wrench has a curved armwith a lug or hook on the end. This lug fits into one ofthe notches of the nut and the handle is turned toloosen or tighten the nut. This spanner may be madefor just one particular size of notched nut, or it mayhave a hinged arm to adjust it to a range of sizes.Another type of spanner is the pin spanner. Pinspanners have a pin in place of a hook. This pin fitsinto a hole in the outer part of the nut.Face pin spanners are designed so the pins fit intoholes in the face of the nut (fig. 2-3).When you use a spanner wrench, you must ensurethe pins, lugs, or hooks make firm contact with the nutwhile the turning force is applied. If this is not done,damage will result to either personnel, tools, or equip-ment.SETSCREW WRENCHES(ALLEN AND BRISTOL)In some places it is desirable to use recessed headson setscrews and capscrews. The Allen screw is usedextensively on office machines and in machine shops.The Bristol is used infrequently.Figure 2-3.—General purpose spanner wrenches.Recessed head screws usually have a hexshaped(six-sided) recess. To remove or tighten this type ofscrew requires a special wrench that will fit in therecess. This wrench is called an Allen wrench. Allenwrenches are made from hexagonal L-shaped bars oftool steel (fig. 2-4). They range in size up to 3/4 inch.When using the Allen wrench, make sure you use thecorrect size to prevent rounding or spreading the headof the screw. A snug fit within the recessed head of thescrew is an indication that you have the correct size.The Bristol wrench is made from round stock. Itis also L-shaped, but one end is fluted to fit the flutesor little splines in the Bristol setscrew (fig. 2-4).Figure 2-4.—Allen and Bristol wrenches.2-3
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