Shop Information Study Guide for McGraw-Hill's ASVAB (page 7)

Practice problems for this study guide can be found at:

Shop Information Practice Problems for McGraw-Hill's ASVAB

The shop information questions that appear on the ASVAB measure how much you understand about shop tools, practices, materials, and procedures. The questions may ask you to identify a particular shop tool, to tell how it is used, or to choose the correct procedure when working with wood, metal, or construction materials. If you took shop courses in high school, or if you have done any woodworking or metalworking on your own, you may already be familiar with many of the topics covered on the test. You may also have learned shop and construction tools and procedures on the job.

On the paper-and-pencil version of the ASVAB, shop questions are one part of the Auto and Shop Information test. On the CAT-ASVAB, they form a separate test of their own.

Whichever ASVAB version you take, you'll have only about half a minute to answer each shop information question, so you'll have to work fast if you want to get a good score. That's why it pays to spend time studying the test topics and tackling plenty of sample ASVAB shop information questions.

The topic review that follows will help prepare you to answer ASVAB shop information questions. It lists and describes the different tools you should know, with an emphasis on traditional hand tools. It also covers common fasteners and materials. There is also important information about tool safety.

Measurement and Layout

New projects and many repairs start with measurement and layout. This is where you amass the proper tools and materials, and mark out the cutting and drilling.

Measuring Tools

Carpenters usually use a tape measure, marked in 1/16-inch increments. The tape retracts automatically into the case, but locks in place when it must be extended for a while. The tape has a hook on the end that moves slightly for accurate inside and outside measurements. Retractable tape measures range from 6 feet to 25 feet long.

When greater accuracy is needed, machinists use a rigid steel rule. These rules are often marked in 1/32- or 1/64-inch increments and are often 1 foot long. A metric steel rule would usually be marked in 1-millimeter increments.

When even greater accuracy is needed, machinists use calipers or micrometers. Some calipers are simply two legs that can transfer a measurement to a steel rule. These calipers can take inside or outside measurements, depending on the shape of the legs. Calipers can also have straight legs.

The Vernier caliper is even more accurate, thanks to the clever Vernier system. First identify the Vernier scale and the main scale. Now look at the "0" on the Vernier scale (see Figure S-3). This is just past the third mark on the main scale, indicating 3 millimeters (mm) on this metric caliper. So the measurement is a bit more than 3 mm, but how much more? Notice that line 3 on the Vernier scale lines up with a line on the main scale. That means that you should add 0.3 mm to the measurement, making a total of 3.3 mm. (Only one mark on the Vernier scale will line up with the main scale, and it doesn't matter which line it lines up with. Remember, read the number on the Vernier scale to get the right-hand digit in the measurement.)

Micrometers are even more accurate than Vernier calipers, but they are usually designed to read only in a certain range, say up to 1 inch, or 1 inch to 2 inches. Unlike a Vernier caliper, where you slide the adjuster, you turn a screw on a micrometer.

Layout often calls for square (90°) lines. A carpenter's square is used to draw these lines: When you hold one leg against the edge of a board, the second makes a square line across the board. A smaller version is called the try square.

You may also see a sliding bevel, which has a metal leg fastened to a wooden block. By loosening the adjustment screw, you can set the tool to mark almost any angle. Sliding bevels can be used to transfer angles from place to place.

The easiest way to tell if something is level (horizontal) or vertical (plumb) is with a level, sometimes called a spirit level. Levels use glass or plastic tubes that are curved or slightly swollen in the middle. When the bubble in the liquid (spirit) is centered, the level is horizontal or vertical.

Cutting and Shaping

After the layout step is done, it's time to cut and shape the materials. We'll take up woodworking tools first, then metalworking tools.

Woodworking Tools

Sharp hand saws are the most basic way to cut wood. Saws cut a kerf that is wider than the blade itself; the kerf allows the saw to move freely through the cut. Crosscut saws are designed to cut at 90° to the grain, while ripsaws cut parallel to the grain. Ripsaws have larger teeth. Backsaws have a rigid steel backing that improves accuracy; they are used in miter boxes that guide them for 45° or 90° cuts.

Keyhole saws are made to cut complicated profiles. An electric version is called the jigsaw. A coping saw has a thin blade held in a P-shaped handle. The saw is used to cut molding.

An electric circular saw, usually with a 7-1/4-inch-diameter blade, is much faster for cutting wood, especially for ripsawing, and for sawing plywood or other panels. These saws are dangerous; read the instruction manual carefully.

Wood chisels, sold in widths from 1/4 inch to 1-1/2 inches, cut wood when they are struck with a hammer or mallet.

A hand plane removes thin strips of wood and is used to shape, smooth, or reduce the size of boards. It's especially useful for removing saw marks from the edge of a board. The "jack" plane is a generalpurpose type of hand plane.

Metalworking Tools

A hacksaw has a replaceable metal blade with small teeth and is that is used for cutting iron, steel, and other, softer metals. Choose a blade with finer teeth for thinner metal, and one with larger teeth for thicker metal. The hacksaw should cut on the forward stroke.

Tin snips cut steel, copper, or aluminum sheet metal, using a shearing action. Some snips have replaceable blades; others can be sharpened. Special snips are designed to cut curves.

A right-angle grinder can polish metal before painting, or otherwise smooth or shape metal. Grind toward the edge of the wheel; do not hold it flat to the surface of the metal. The same tool will also drive a wire brush for removing rust.

A pipe cutter—used for copper, not steel, pipe—has a sharp cutting wheel. Gradually tighten the handleas you rotate the tool around the pipe.

Taps and dies cut or restore threads in metal. A die cuts threads on a rod; a tap cuts threads in a hole drilled in a plate. Either tool can be used to restore mangled threads. Both taps and dies cut only one diameter and pitch (number of threads per inch). To select a die, you must know the outside diameter (O.D.) of the pipe.

Drills and Drilling Tools

Electric drills have become a centerpiece of all workshops, for making holes, driving screws, and other purposes. Drills are sized by the largest diameter of bit that will fit in the chuck (the rotating clamp that holds the bit). You sometimes see 1/4-inch drills, but 3/8-inch drills are an all-around tool for the home workshop. Larger drills handle bits of 1/2- or 3/4-inch diameter. However, the shank (the part that gets grabbed in the chuck) can be smaller than the tip of the drill bit, so it's possible to drill 1-inch holes in wood with a 3/8-inch drill.

Iron and steel are much harder to drill than wood, and thus call for a larger, more powerful drill. Often, it's best to drill a small "pilot" hole in metal. This is because metal-cutting drill bits have a blind spot near the center where they don't drill very well. The pilot hole makes a clear space for the blind spot on the larger drill. While drilling metal, it often helps to oil the bit for cooling; excess heat can destroy the heat treatment that makes a bit hard enough to cut metal.

The chuck may be tightened with a chuck key, as shown. Newer, self-tightening chucks do not use a key. Instead, the parts tighten when they are turned against each other.

The helix on a twist drill brings chips up out of the hole. Twist drills will start accurately in wood, but they wander across the surface in metal. A center punch makes a dimple in metal to locate the bit as it starts to drill. Use a hammer to hit the center punch.

Auger bits are made only for wood, which they cut much faster than twist drills. Auger bits were originally driven by a brace and bit, but they can also be used in electric drills.

A countersink is a conical depression in a surface that allows a flat-head screw to sit flush (flat) to the surface. A special drill bit, also called a countersink, makes the countersink.

A hole saw makes large-diameter holes in wood and some metals. The type of hole saw shown screws onto a mandrel, allowing one mandrel to handle several size saws. Hole saws are more economical than big drills for drilling wood, but they do not work in hard metal.

Pounding Tools

Many of the oldest tools are designed to hit something. A claw (carpenter's) hammer pounds nails with the face and pulls them with the claw. A straight claw is better for longer nails, and is also handier for doing demolition. Some hammer faces have a checkered pattern, called a waffle head, to increase the grip on the nails. The standard size of claw hammer is 16 oz. Hammers 24 oz. in size are used for large nails.

Metal workers use a ball-peen hammer. One face is flat, like a claw hammer, the other face has a ball peen, used for shaping metal and riveting. Ball-peen hammers may weigh up to 3 lb.

Sledgehammers are used for heavy purposes. Some people can swing the hand sledge shown here with one hand. True sledgehammers have a 32-inch handle and require two hands.

A rubber mallet may be used to adjust parts without damage, or to drive wooden-handled chisels. Wooden mallets are also used for striking chisels. Many modern chisels, however, have steel shanks and can safely be struck with a hammer.

Tools For Turning or Grabbing

Shop work, including maintenance and repair, requires a good assortment of tools that turn or grab. An adjustable (Crescent) wrench can be adjusted to hold various sizes of hexagonal or square bolts. Typical overall lengths range from 6 to 12 inches.

A combination wrench combines two basic types of wrench: the box-end and the open-end wrench. Each end of a combination wrench fits the same size bolt. Because most bolt heads have six faces (called hexagonal bolts or hex bolts) the box end has 6 or 12 facets. With 12 facets, you can turn the wrench 1/12 of a turn, which is handy in tight quarters. That's why they are offset 15° at the end.

A socket wrench holds a bolt or nut from above. The deep socket, shown, allows you to grab a nut even if some threads are sticking out above it. Socket wrenches connect to the sockets with a square drive; possible drive dimensions include 1/4, 3/8, 1/2, or 3/4 inch. Larger drives are available for heavier-duty use.

A ratchet wrench is one way to drive a socket. It will grab when it swings in one direction and slip in the other, for convenient tightening or loosening.

A torque wrench fits a socket and drives bolts to a specified tightness. You can buy them marked in American or metric units.

An Allen wrench fits screws with a hexagonal recess in the head. Allen wrenches are sold in inches and millimeters.

Arc-joint pliers (often called Channel Locks) are used to grab various sizes of material. To adjust the jaws, open them wide and engage a different set of arcs. Arc-joint pliers are not good for grabbing bolts or nuts, as they will scar the metal.

Locking pliers (often called Vise Grips) have a lever system that gives a very strong, locking grab. They are one of the handiest tools in the box, but they can damage bolts and nuts.

A needle-nose (longnose) pliers gets at small parts and is especially handy for electric wiring.

A bar clamp, among other types of clamp, can hold parts in position while you work or hold joints while the glue sets.

A pipe wrench has steel teeth that hold steel pipe. They are sold in lengths ranging from 12 to 48 inches. Flip the wrench over to turn the pipe in the other direction.

Flat-bladed (standard) screwdrivers are a major part of any toolbox. They come in many sizes. A long shank will protect your hands when you are pressing hard.

A Phillips screwdriver drives Phillips screws—the ones with a cross-shaped head. They also are sold in various sizes.

Fasteners and Fastening Techniques

Keeping things together requires a variety of different types of fasteners. We'll start with threaded fasteners and nails, then move to fasteners that use molten metal.

Threaded Fasteners

Some threaded fasteners—screws and bolts—are designed to cut threads in the material. These wood and sheet-metal screws come in many sizes and materials, with any number of head styles. Sheet-metal screws cut threads in sheet-metal.

Wood screws are sized by length and diameter. Length is measured in inches; diameter by a numbering system (#6, #8, #10, and so on). Larger numbers indicate a larger diameter.

A separate category of threaded fasteners uses what are called machine threads. These screws and bolts must be screwed into a nut with the same diameter and number of threads per inch (also called pitch). Most machine threads are right-hand, meaning that they tighten when you turn the top to the right—clockwise. Left-hand bolts tighten in the opposite direction. Machine screws often use lock washers to prevent the nut from loosening. The lock washer is compressed under the nut and holds the nut tight.

A hex bolt is a machine screw. It can range in diameter from 1/4 inch on up, and in length from 1/2 inch on up.

A carriage bolt is a machine screw with a round head and a square shank. The shank fits a square slot, so the bolt does not turn while being tightened. The large head substitutes for a flat washer, distributing the bolt's force across a wider area.

Nails

Nails are an ancient form of fastener, but they have gotten a lot more complicated over the past 20 years. Let's start with some terminology:

• Brad: A small, thin nail with a small head, used for picture frames and other light fastening.
• Tack: A small nail with a big head, used to attach carpet and upholstery.
• Finishing nail. A sturdy, small-diameter nail with a small head, used to attach trim and molding.
• Common nail: A big, large-headed nail used for rough construction.
• Sinker: A smaller-diameter version of the common nail that causes less splitting.
• Spike: A heavy, large nail for fastening timbers.
• Ring-shank: A nail with rings that improve grip.
• Spiral: A nail with a spiral on the shank, used to increase grip, for example, on flooring nails.

Nails are sized by length and by pennies ("d"). A 4d nail is 1-1/2 inches long, while a 16d nail is 3-1/2 inches long. Nails are sometimes coated with zinc (galvanized) to resist rust. These days, nails are often driven with pneumatic devices called nail guns.

When selecting a nail, choose a large head to hold soft materials and a small head for an exposed location. In construction, structural nails must grab about 1-1/2 inches. A larger diameter gets a stronger grip, but is also more likely to split the wood. Finally, for strength, a ring- or spiral-shank nail is a good choice.