Materials, Fasteners and Shop Processes

🔩 Materials, Fasteners and Shop Processes

Part 1 of 7 — Materials and Fasteners on the ASVAB

The other half of Shop Information

The Shop Information (SI) subtest covers "shop tools, building materials, and building and construction procedures" and "wood and metal shop practices." The Hand and Power Tools lesson covered the tools. This lesson covers everything else:

• Fasteners: which nail, screw, bolt, nut, washer or rivet fits the job
• Wood and building materials: hardwood and softwood, plywood, lumber sizes, framing, drywall, concrete, wood joints
• Metal and shop processes: kinds of metal, sheet-metal gauge, soldering, brazing, welding, sanding and finishing

Same clock as before

SI is not part of the AFQT, but your Auto and Shop results combine into the AS score, which appears in mechanical line scores such as Air Force M, Marine Corps MM, Navy MEC and ENG, and the Army's MM area (driven mostly by AS, MC and EI).

What these questions look like

• "Which fastener should be used to hang a heavy shelf on a hollow drywall wall?"
• "What does the d in 16d nail stand for?"
• "What are the actual dimensions of a $2 \times 4$?"
• "Which joining process melts the base metal?"
• "Which sandpaper grit is the finest?"

Nearly all of them reward one idea: every material and fastener has a job it was designed for.

The plan for this lesson

Four fastener families at a glance

Rule of thumb: nails are fastest and resist sideways (shear) loads well; screws resist pulling out better; bolts carry the heaviest loads and come apart for service; rivets are permanent.

Warm-up 1. Use the figure. 🎯

Warm-up 2 and 3. 🎯

Key Takeaways — Part 1

• SI also tests fasteners, building materials and shop processes, still 10 questions in 6 minutes on the CAT
• Nails: fast, good in shear. Screws: resist pulling out. Bolts: heavy loads, removable. Rivets: permanent
• Every question reduces to: what was this material or fastener designed to do?

Up Next: Part 2 — nails and screws: types, penny sizes, heads and pilot holes.

🔩 Materials, Fasteners and Shop Processes

Part 2 of 7 — Nails and Screws

Nail types: read the head and the shank

Galvanized nails have a zinc coating that resists rust, so they are used outdoors and with treated lumber.

Penny sizes: the "d" is a length

Nail length is given in penny size, written with a d (16d is "sixteen-penny"). The number is a length code, not a price today.

From 2d to 10d, each penny adds $\frac{1}{4}$ inch: $\text{length} = 1 + \frac{1}{4}(\text{penny} - 2)$ inches. So a 7d nail is $1 + \frac{5}{4} = 2\frac{1}{4}$ inches.

Worked example. How long is a 9d nail? $1 + \frac{1}{4}(7) = 2\frac{3}{4}$ inches. Bigger penny number, longer nail.

Good practice: nail through the thinner piece into the thicker one. A common rule of thumb is a nail about three times as long as the thickness of the board you nail through. Clinching (bending over a nail point that pokes through) adds holding power, and toenailing means driving nails at an angle through the end of one board into another.

Four nails. Use the figure. 🎯

Penny sizes. ✍️ Use the table or the rule $1 + \frac{1}{4}(\text{penny} - 2)$ for sizes 2d through 10d.

1) Length of a 6d nail, in inches (number only):

2) Length of a 10d nail, in inches (number only):

3) Length of a 5d nail, in inches (decimal or fraction):

Screws: match the thread to the material

Heads

Pilot holes

A pilot hole (a little narrower than the screw's threads) keeps hardwood from splitting and makes driving easier. In the top board, a clearance hole as wide as the shank lets the screw pull the boards tightly together.

Worked example. A ventilation duct of thin galvanized steel needs a bracket attached. The right choice is a sheet-metal screw: sharp point, threads that bite thin metal.

Four screws. Use the figure. 🎯

Nails and screws in practice. 🎯

Key Takeaways — Part 2

• Common = framing; box = thinner, splits less; finishing/casing/brad = trim, set below the surface; roofing = wide head; duplex = temporary
• Penny (d) is a length: 2d = $1$ in., add $\frac{1}{4}$ in. per penny to 10d = $3$ in.; 16d = $3\frac{1}{2}$ in.
• Wood screw (tapered), sheet-metal screw (threaded to a sharp point), machine screw (blunt, into a nut or tapped hole), lag screw (hex head, wrench, heavy timber)
• Flat heads sit flush in a countersink; drill pilot holes in hardwood
• Screws resist pulling out; nails are fast and good in shear

Up Next: Part 3 — bolts, nuts, washers, rivets and threads.

🔩 Materials, Fasteners and Shop Processes

Part 3 of 7 — Bolts, Nuts, Washers, Rivets and Threads

Bolts: clamp the parts between a head and a nut

Wall anchors (plastic sleeves, expansion anchors, molly bolts) work like toggle bolts on a smaller scale: they expand inside a drilled hole so a screw holds in drywall, masonry or concrete.

Worked example. A heavy mirror must hang on a drywall wall where there is no stud behind it. A plain screw would pull out of the soft gypsum. A toggle bolt opens its wings behind the drywall and spreads the weight over a large area.

Four bolts. Use the figure. 🎯

Nuts and washers

Worked example. A bolt holding a lawnmower handle keeps working loose from vibration. Two good fixes: a lock nut (nylon insert) or a split lock washer under a regular nut.

Four nuts. Use the figure. 🎯

Threads and rivets

Reading a thread size

A bolt marked $\frac{3}{8}$-16 has a diameter of $\frac{3}{8}$ inch and 16 threads per inch (TPI). The pitch is the distance from one thread to the next: with 16 TPI, the pitch is $\frac{1}{16}$ inch. A nut moves one pitch per full turn.

Worked example. How many turns does it take to run a nut $\frac{3}{4}$ inch along a $\frac{1}{2}$-20 bolt? Each turn moves $\frac{1}{20}$ inch, so it takes $\frac{3}{4} \times 20 = 15$ turns.

• A tap cuts threads inside a hole (drill the tap-drill hole first). A die cuts threads outside on a rod. A thread gauge checks the pitch.
• Almost all threads are right-hand: turn clockwise to tighten ("righty-tighty, lefty-loosey"). A few parts use left-hand threads so they will not loosen as they spin.

Rivets

• A solid rivet is pushed through both pieces, then its tail is hammered or squeezed flat, often with a ball-peen hammer and a backing tool. You need access to both sides.
• A pop (blind) rivet is set with a rivet tool from one side only: pulling a mandrel through the rivet swells its far end. Use it when you cannot reach the back, as on a closed box beam or a trailer wall.
• Rivets are permanent; to remove one, you drill out its head.

Thread math. ✍️ A bolt is marked $\frac{1}{4}$-20.

1) How many threads per inch does it have? (number only)

2) What is its pitch, in inches? (fraction or decimal)

3) How many full turns move a nut $\frac{1}{2}$ inch along this bolt? (number only)

Threads, washers and rivets. 🔽

Key Takeaways — Part 3

• Carriage bolt = wood, square neck stops spinning; toggle bolt = hollow walls; hex bolt = machinery; anchor bolt = set in concrete
• Wing nut = by hand; lock nut = resists vibration; castle nut + cotter pin = axles; acorn nut = covers the end
• Flat washer spreads load; split lock washer resists loosening; fender washer = big diameter for thin stock
• $\frac{3}{8}$-16 = diameter $\frac{3}{8}$ in., 16 TPI; one turn moves one pitch ($\frac{1}{\text{TPI}}$ in.)
• Tap = inside threads, die = outside threads; right-hand threads tighten clockwise
• Pop rivets go in from one side; solid rivets need both sides; rivets are permanent

Up Next: Part 4 — wood, lumber and building materials.

🔩 Materials, Fasteners and Shop Processes

Part 4 of 7 — Wood, Lumber and Building Materials

Hardwood and softwood

The names describe the tree, not how hard the wood feels.

• Grain is the direction of the wood fibers. Wood splits easily along the grain and is strongest along its length.
• Wood shrinks and swells with moisture. Lumber that dries unevenly warps: it can cup, bow or twist.
• Pressure-treated lumber is soaked with chemicals that resist rot and insects, for ground contact and outdoor framing. Cedar and redwood resist rot naturally.

Engineered panels

Worked example. Why does plywood resist splitting better than a solid board of the same thickness? Its plies cross at right angles, so no single grain direction runs all the way through. A crack that starts along one layer's grain is stopped by the next layer.

Lumber sizes: nominal versus actual

Lumber is named by its rough-sawn size (nominal). Drying and planing make it smaller (actual).

Pattern: a "2-by" is $1\frac{1}{2}$ inches thick; widths up to 6 lose $\frac{1}{2}$ inch.

Board feet

A board foot is $1$ inch $\times$ $12$ inches $\times$ $12$ inches $= 144$ cubic inches of wood (using nominal sizes).

$\text{board feet} = \frac{\text{thickness (in.)} \times \text{width (in.)} \times \text{length (ft)}}{12}$

Worked example. A $2 \times 8$ that is $6$ feet long contains $\frac{2 \times 8 \times 6}{12} = \frac{96}{12} = 8$ board feet.

Framing a wall

• Studs (usually $2 \times 4$ or $2 \times 6$) stand vertically, normally 16 inches on center (measured center to center), sometimes 24.
• The bottom (sole) plate and top plate run along the floor and ceiling. A header spans the top of a door or window opening. Joists hold up floors and ceilings; rafters hold up the roof.
• Drywall (gypsum board) is screwed or nailed to the studs, and its seams are covered with tape and joint compound.

Worked example. A wall $12$ feet long gets studs 16 inches on center. $12$ ft $= 144$ in., and $144 \div 16 = 9$ spaces. Nine spaces need 10 studs (one more stud than spaces).

Lumber math. ✍️

1) The actual width, in inches, of a nominal $2 \times 6$ (decimal or fraction):

2) The board feet in a $2 \times 6$ that is $12$ feet long (number only):

3) A wall $16$ feet long is framed with studs $16$ inches on center. How many studs does it need, counting both ends? (number only)

Wood and panels. 🎯

Concrete, mortar and wood joints

Concrete and mortar

• Concrete = cement + sand (fine aggregate) + gravel (coarse aggregate) + water. The cement and water react chemically and harden around the aggregate.
• Concrete cures, it does not simply dry. Keeping it moist for the first several days makes it stronger, and it keeps gaining strength for weeks.
• Concrete is very strong in compression (being squeezed) and weak in tension (being pulled), so slabs and beams get steel rebar or wire mesh.
• Mortar (cement, sand, lime and water) bonds bricks and concrete blocks together.

Wood joints

Four joints. Use the figure. 🎯

Concrete and framing. 🎯

Key Takeaways — Part 4

• Hardwood = broad-leaf trees (oak, maple); softwood = conifers (pine, fir), used for framing
• Plywood plies cross at right angles: strong both ways, resists splitting; OSB = sheathing; particleboard is weak when wet
• Nominal $2 \times 4$ = actual $1\frac{1}{2} \times 3\frac{1}{2}$; board feet $= \frac{T \times W \times L_{\text{ft}}}{12}$
• Studs 16 in. on center; studs = spaces + 1
• Concrete = cement + sand + gravel + water; it cures (keep it moist); rebar carries tension
• Joints: miter $45^\circ$, dado groove across the face, rabbet notch on the edge, mortise and tenon strong, dovetail resists pulling apart

Up Next: Part 5 — metals, welding, soldering and finishing.

🔩 Materials, Fasteners and Shop Processes

Part 5 of 7 — Metals, Welding, Soldering and Finishing

Ferrous and nonferrous metals

Ferrous metals contain iron. Most are magnetic, and plain ones rust. Nonferrous metals contain little or no iron.

• Galvanized steel is coated with zinc to keep it from rusting.
• Heat treating (recognition level): hardening heats steel and cools it quickly; tempering reheats hardened steel to make it less brittle; annealing heats metal and cools it slowly to make it softer and easier to work.

Sheet-metal gauge: bigger number, thinner metal

Sheet metal and wire are sized by gauge. The higher the gauge number, the thinner the metal. A $10$-gauge sheet is much thicker than a $22$-gauge sheet.

Worked example. A truck bed liner must resist dents; a heating duct just has to carry air. The liner gets a low gauge number (thick metal), and the duct gets a high gauge number (thin metal).

Metals. 🎯

Joining metal: solder, braze or weld

The key question is: does the base metal melt?

• Flux cleans the metal and keeps oxygen away so the filler flows and sticks. Electronics use rosin-core solder; the acid flux used for plumbing would corrode circuit boards.
• In soldering and brazing the filler is drawn into the joint like water into a sponge, so the parts must be clean and tight-fitting.

Kinds of welding (recognition level)

Welding safety: an arc gives off intense ultraviolet light that burns your eyes and skin. Wear a welding helmet with the correct shade of lens (ordinary safety glasses are not enough), leather gloves and sleeves, and work with ventilation and a fire extinguisher nearby.

Joining processes. 🎯

Sanding and finishing

Sandpaper grit: bigger number, finer paper

The grit number counts the abrasive particles per area, so a higher number means smaller particles and a finer, smoother cut.

• Work from coarse to fine, and don't skip too many grades.
• Sand with the grain. Sanding across the grain leaves scratches that stain makes even more obvious.
• Wipe off the dust with a tack cloth before applying any finish.

Finishes

Worked example. You're refinishing a table: strip the old finish, sand with 80, then 120, then 180 grit, wipe with a tack cloth, stain, and protect with polyurethane.

Sanding and finishing. 🔽

Key Takeaways — Part 5

• Ferrous = contains iron (cast iron, steel); nonferrous = aluminum, copper, brass, bronze
• Cast iron is brittle; stainless resists rust; galvanized = zinc coating; annealing softens
• Sheet-metal gauge: higher number = thinner
• Soldering (lowest heat) and brazing do not melt the base metal; welding does. Flux helps filler flow; rosin-core for electronics
• Arc welding needs a welding helmet, not safety glasses
• Sandpaper: higher grit = finer; go coarse to fine, with the grain; primer before paint, stain colors wood

Up Next: Part 6 — test strategy and the traps in materials and fastener questions.

🔩 Materials, Fasteners and Shop Processes

Part 6 of 7 — Materials and Fasteners Test Strategy and Traps

Timing

Shop Information gives you $10$ questions in $6$ minutes, about $36$ seconds each, and materials and fastener questions share that clock with the tool questions.

• Fact questions ("What does d mean in 16d?") should take under 15 seconds. Answer, move on, bank the time.
• Number questions (penny length, board feet, actual lumber size, turns of a nut) need a quick line of scratch work. Write it; don't juggle it in your head.
• You must answer to move on and cannot return, so commit to your best answer. Treat every question as scored, since tryout items look the same.

A routine for fastener and material questions

1. What is being joined or built? Wood to wood, metal to metal, something to a hollow wall, something to concrete?
2. What does the joint need? Permanent or removable? Resist pulling out, resist vibration, sit flush, survive outdoors?
3. Pick the item designed for that job, not one that could merely be forced to work.

Worked example. "What is the best way to attach a heavy coat rack to a concrete block wall?" Joined to: masonry. Needs: strong, removable screws. Answer: drill with a masonry bit and use masonry anchors (expansion anchors) with screws or bolts. A toggle bolt is for hollow drywall; nails will not hold in block.

The number traps

These four scales go in opposite directions, and test writers know it.

The word traps

Spot the trap. 🎯

Speed drill. Under 15 seconds each. ⏱️

Key Takeaways — Part 6

• Fact questions in under 15 seconds; number questions with one line of scratch work
• Routine: what is joined → what the joint needs → the item designed for it
• Bigger number: penny = longer, gauge = thinner, grit = finer, TPI = finer thread
• Always use actual lumber sizes for math
• Tap inside, die outside; solder/braze never melt the base metal, welding does

Up Next: Part 7 — a mixed mastery set for materials, fasteners and shop processes.

🔩 Materials, Fasteners and Shop Processes

Part 7 of 7 — Materials, Fasteners and Shop Processes Mastery Set

This set mixes fasteners, wood and building materials, metals, joining and finishing the way the Shop Information subtest does. Keep a test-day pace: about 36 seconds per question, with one line of scratch work for anything numerical.

Question 1. Use the figure. 🎯

Question 2. Use the figure. 🎯

Questions 3 to 6. 🎯

Questions 7 to 10. 🎯

Lesson Wrap-Up

Next steps: take the exit quiz for this topic. That completes Shop Information. Next comes Mechanical Comprehension.