Wrenches
Open-end wrenches
The open-end wrench is the sim-plest type. It has one or two C-shaped ends with flat sides that fit over a hex-head bolt. By pulling on the handle of the wrench, you can turn the bolt. When you apply force to the handle of the wrench to turn a tight bolt, the flat sides of the open-end wrench bear on two corners of the bolt. This tends to round off those corners, and to spread the parallel sides of the wrench opening. If the bolt is a tight one, you may round it off so much that you cannot get it out at all. The better the wrench, the more closely it will fit the bolt. So a good open-end wrench really works better than a cheaper one, and it is often lighter as well. The least expensive open-end wrenches are made from stamped sheet steel. They bend easily, and round off nuts and bolts. Do not buy them.
Better open-end wrenches are made from steel forgings shaped to fit your hand as well as a specific size hex-head nut or bolt. Some pretty good ones are left just as they were forged, with the exception of the openings that are machined to size. These are the leastexpensive of this type and will serve you well.
For very little extra, you can buy chrome-plated wrenches which look a lot better, will not rust, and are easier to wipe clean. They are also a lot nicer to use. Most home mechanics and many professionals use them. Slightly better finish and tougher steels drive the price up fast, making the best wrenches several times as costly as the ordinary ones. Handle some and examine them before deciding what will do the job to your satisfaction.
A wrench is the first tool you think of when you consider automotive tools. Ever since the first car was bolted to-gether some time in the last century, bolts have been holding cars and mostof their parts together. To turn a bolt, you use a wrench. Since the bolts hold-ing your car together are hidden in vari-ous inaccessible places, it takes a great variety of wrenches to turn all of them.
Most wrenches come in sets of six to 12 units, but you can buy them individ-ually. It will usually pay to buy a standard set of open-end wrenches. Sooner or later, you will come across fasteners of most common sizes. Besides, each wrench in a set costs less than when bought separately.
Inches vs. metric
If you have an American car;with a couple of notable exceptions;it will have standard US SAE, Society of Automotive Engineers, fasteners. These are measured in inches across the flats of the hexagonal head. A 9A6-inch open-end wrench will be about .005-inch larger than 9A6-inch between the sides of its opening to fit a 9/,,-inch hex-head.
But the metric system is com-ing. By about the mid-1980's, you will need metric wrenches to work on any car from any country. Now you need them for European and Japanese cars plus the engine on the Ford Pinto and just about everything on the Chevrolet Chevette.
GeneralMotors is designing all new com ponents according to the metric system, so more and more metric tools will be required. The other car makers will not be far behind. At the end of this chapter you will find inches-to-metric conversion tables.
Box wrenches
The next most common type of wrench is a box wrench. Like the open-end, it is made from a steel bar, but the opening forms a ring rather than a letter C. The inside of the ring is shaped in the form of a six-sided or 12-sided figure to fit over a hexagonal nut or bolt. The box or ring will not spread the way the jaws of an open-end wrench will, and the sides grip all six corners of the nut. So, with a box wrench, you can apply a lot more torque to a tight nut or bolt without the risk of slipping off it or rounding off the corners. The disadvantage is that you have to lift the box opening off the nut every time you reposition the wrench for another swing. This is slower than slipping an open-end wrench over the nut.
Six-point openings let you twist harder, but the more common 12-pointers fit on the fastener in more positions;an advantage when working in tight quar-ters. For larger nuts, 12-point box wrenches work fine, but for really tiny ones, six-point wrenches sometimes work better.
Adjustable wrenches
These descendants of the now nearly forgotten monkey wrench are often necessary when you cannot carry a complete set of fixed-opening wrenches with you, or for turning nuts and bolts of odd sizes which you encounter so rarely it does not seem worth getting a special wrench to fit them. When using an adjustable wrench, set it to fit the fastener tightly, then pull on the handle on the same side as the stronger fixed jaw to loosen a tight bolt.
Adjustable wrenches are weaker than those with fixed openings. Check an adjustable wrench carefully before you use it. Make sure the jaws are parallel when you look at the end and the side of the wrench, that they are not wobbly, and that there are no cracks, particularly in the narrow web area where the movable jaw fits into the body of the tool. The adjustment screw should turn smoothly throughout the full range of openings. Some of the latest adjustable wrenches have a locking feature which clamps the jaws a bit tighter on the bolt you are turning and locks them there. These are expensive, but they are the best type of adjustable open-end wrench for the amateur mechanic since they are less apt to round off nuts and bolt heads.
|
