Shop Information: mixed review

Open-end: U-shaped jaw slides on from the side when a closed ring cannot fit over the nut, but it grips fewer faces. Box-end: closed ring surrounds the head for firmer grip; preferred to break loose a stubborn fastener.

$\tau =Fr\sin \theta$, F in newtons, r in meters, $\tau$ in N·m; $\theta$ is between handle and force. 100 N at 0.20 m gives 20 N·m when perpendicular but 10 N·m at 30°.

Only the product matters: $\tau =Fr$. Doubling the handle length doubles torque for the same force; 40 N at 0.25 m and 25 N at 0.40 m both give 10 N·m. Improvised pipe extensions can overload the tool.

No. $0.5\times 25.4=12.7$ mm, and 3/4 inch is 19.05 mm, not 19 mm. Near sizes can still round a fastener; check actual fit rather than rounding.

A rip saw cuts wood along (with) the grain; a crosscut saw cuts across the grain; a coping saw has a narrow blade in a deep frame for curves and intricate cuts in thin wood.

A center punch makes a small dimple to locate a drill start so the bit does not wander. A pin punch drives out pins; a pointed center punch could spread or deform a pin.

Install the blade with teeth pointing away from the handle, so the saw cuts on the push (forward) stroke. Choose a suitable tooth pitch, tension the blade and secure the work first.

A mushroomed chisel or punch head (fragments can fly off), a cracked, splintered or loose hammer handle, and a wrench with sprung jaws that slips. Do not just grip harder or rely on gloves.

$1\text{ in}=25.4\text{ mm}$ exactly. Multiply inches by 25.4 to get mm; divide mm by 25.4 to get inches. 1/2 in = 12.7 mm and 1/4 in = 6.35 mm (not 0.25 mm).

Accuracy: closeness to the accepted reference value. Precision: repeatability among repeated readings. Resolution: smallest displayed increment. More display digits do not make a tool accurate.

Spindle moves 0.5 mm per turn and the thimble has 50 divisions, so each is 0.01 mm. Reading = sleeve + thimble $\times$ 0.01: sleeve 7.5 mm, thimble 23 gives 7.73 mm. Do not miss the half-mm line.

Take the main-scale value just before the vernier zero, then add the aligned vernier line times the increment: $12.00+7\times 0.02=12.14$ mm. Check the instrument's own increment.

Upper limit = nominal + plus deviation; lower limit = nominal - minus deviation. For $25.00_{-0.05}^{+0.10}$ mm the band is 24.95 to 25.10 mm, so 24.94 mm fails.

Diametral $C=D_{\text{hole}}-D_{\text{shaft}}$; centered radial clearance is half that. 15.20 mm and 15.05 mm give 0.15 mm diametral, 0.075 mm radial. A negative result suggests interference.

Subtract the start reading from the end reading. A part from the 1-inch line to 1 11/16 inches is 11/16 inch long; from 2 to 7 3/8 inches is 5 3/8 inches. Do not report the endpoint as the length.

Legs of 3 and 4 units give a diagonal of 5 when square: $\sqrt{300^2+400^2}=500$ mm. Multiples like 6-8-10 also work; measure both legs and the diagonal.

A bolt usually passes through clearance holes and takes a nut. A screw engages threads in a part or forms its own. A stud is threaded at both ends or along its length and stays in one part while a nut goes on the exposed end. A nut is internally threaded.

Metric thread with an 8 mm nominal major diameter (not the hex head width) and a pitch of 1.25 mm, the axial distance from one crest to the next. M10 x 1.5 and M10 x 1.25 are different threads.

$p=\frac{1}{\text{TPI}}$ inches. 1/4-20 means a 1/4 in nominal diameter with 20 threads per inch, so $p=0.050$ in; 16 TPI gives 0.0625 in. TPI is not a torque or a pitch in mm.

Lead $L=np$, n = number of starts. Single-start: lead equals pitch; a two-start 1.5 mm pitch thread advances 3.0 mm per turn. Travel over N turns of a single-start screw is $d=Np$.

A tap cuts or forms internal threads in a prepared hole (tap drill smaller than the major diameter). A die cuts or forms external threads on a rod or bolt.

Preload is the clamping force from tightening: the bolt stretches elastically and the joint compresses. Torque only estimates it, roughly $T\approx KFd$; friction and lubrication change K, so the same torque can give different preload.

No. Matching diameter is not enough; pitch, thread form, handedness and grade must all match. A nut that starts then binds should not be forced; stop and check for wrong pitch or cross-threading.

No. Lock washers do not guarantee vibration resistance; washers cannot fix wrong pitch, length or stripped threads; extra torque can stretch bolts, strip threads or crush gaskets. Use the specified parts and torque.

Direction relative to the grain. A rip cut runs with (along) the lengthwise grain; a crosscut goes across the fibers. Cutting at the end of a board is not automatically a crosscut.

$BF=\frac{T\times W\times L}{144}$ with all dimensions in inches (one board foot is 144 cubic inches). An actual 2 by 6 by 48 inch piece is $\frac{2\times 6\times 48}{144}=4$ board feet.

Kerf is the width of material a saw blade removes. Add it for each cut: three 10-inch blanks with three 1/8-inch cuts need $30+\frac{3}{8}=30\frac{3}{8}$ inches of stock, not 30.

No. A jointer creates a flat reference face or straight edge. A thickness planer makes the opposite face parallel to that reference for consistent thickness; it does not remove twist from a warped board.

A countersink is a conical recess so a flat-head screw sits flush. A counterbore is a flat-bottomed cylindrical recess so a head (such as a socket head) sits below the surface, often covered by a plug.

Dado: a groove across the grain of a board's face, often holding a shelf. Rabbet: an L-shaped recess along an edge or end. Mortise-and-tenon: a cavity (mortise) that accepts a projecting tenon.

Lower grit numbers are coarser and remove material faster; higher numbers are finer and leave a smoother surface. Work through a sequence; very fine grit will not quickly remove deep damage.

No. Surfaced softwood is commonly about 1.5 by 3.5 inches, so its cross-section is $1.5\times 3.5=5.25$ square inches. Use stated or measured actual sizes in calculations.

Lathe: the workpiece rotates while a cutting tool removes material (turning, facing). Milling machine: a rotating cutter removes stock from secured work (slots, keyways, flats). Drill press: the bit rotates and feeds into stationary work.

Facing machines the end of the rotating workpiece flat and perpendicular to its axis. Straight turning reduces the outside diameter along the length of the bar.

Drilling creates the initial round hole with a twist drill. Reaming removes a small amount to improve an existing hole's size and finish. Boring enlarges or refines an existing hole with a single-point cutting tool.

Ferrous metals contain iron as a principal component, such as carbon steel. Nonferrous metals include aluminum, copper, brass and bronze. A magnet test is not a reliable way to determine composition or grade.

Ductility: can stretch a lot under tension before breaking. Malleability: can deform under compression, as when rolled into sheet. Brittleness: fractures with little plastic deformation. None of these is the same as hardness.

Spacing $p=\frac{1}{\text{TPI}}$ inch: 20 TPI gives 0.050 in, or $0.050\times 25.4=1.27$ mm. Higher TPI (finer teeth) generally suits thinner stock.

$v=\pi DN$, D = diameter, N = revolutions per unit time. At the same RPM, a 40 mm workpiece has twice the surface speed of a 20 mm one. Spindle speed is revolutions; cutting speed is linear speed at the edge.

Under OSHA 1910.215, the work rest must be kept closely adjusted with a maximum opening of 1/8 inch (about 3.2 mm), and it is never adjusted while the wheel is turning.

Feed rate = feed per rev $\times$ RPM: 0.10 mm/rev at 600 rpm gives 60 mm/min. Time $t=\frac{\text{travel}}{\text{feed rate}}$: 30 mm at 60 mm/min takes 0.5 min. Multiply, never add, the two given values.

$v_c=\frac{\pi DN}{1000}$, D in mm, N in rpm, $v_c$ in m/min. A 10 mm drill at 1,000 rpm gives about 31.4 m/min. Larger diameter means faster edge speed at the same RPM.

$N=\frac{1000v_c}{\pi D}$, with $v_c$ in m/min and D in mm. At 30 m/min with a 10 mm tool, N is about 955 rpm, before checking machine and material limits.

Work rest (below, supports the work): at most 1/8 inch from the wheel. Adjustable upper tongue guard: at most 1/4 inch. Never adjust either while the wheel is moving; do not swap the two values.

Ask what rotates and what feature results. Rotating bit feeding along its axis: drill press. Rotating workpiece with a moving tool: lathe. Rotating cutter with work fed on a table: mill. Abrasive wheel: grinder.

A power shear cuts sheet metal along a straight line (for example, to reduce width). A press brake bends sheet to an angle with matched tooling, such as forming an L-shaped flange.

Remove it. A key left in the chuck can be thrown out when the spindle starts. Also secure the work in a vise or clamp, never by hand, and stop the machine before clearing chips or measuring.

$V=\pi r^{2}h$, using the radius, not the diameter. A 10 mm hole through 20 mm stock: $\pi \times 5^2\times 20\approx 1571$ mm³.

The base metal itself melts locally at the joint and solidifies into one continuous piece; filler may or may not be added. Heat comes from an electric arc or a gas flame.

Both melt only a filler while the base metal stays solid. Brazing filler liquidus is above 840 °F (450 °C) but below the base metal's melting point; soldering filler melts at or below 840 °F (450 °C).

A consumable coated electrode (rod) supplies filler; its flux coating makes shielding gases and slag that must be chipped off. Clue words: coated rod, electrode holder, slag.

MIG continuously feeds a consumable wire that is both electrode and filler, with shielding gas. TIG uses a nonconsumable tungsten electrode plus shielding gas; filler rod is added separately if needed.

Electrodes squeeze overlapping conductive sheets and pass current; electrical resistance heats the contact spot and pressure forms a weld at discrete spots. Common in high-volume sheet-metal production.

Bolted or screwed joints can be taken apart without destroying the parts. Welds, cured structural adhesives and set rivets are permanent and must be cut, ground or drilled out to separate.

No. Excess filler or adhesive can hide poor wetting, porosity or incomplete fusion. Appearance is not proof of strength, and a hotter process is not automatically stronger.

$\tau =F\times r$: perpendicular force F (N) times moment arm r (m), giving N·m. Example: 20 N on a 0.25 m handle gives 5 N·m. Torque is not the same as bolt preload.

$\rho =\frac{m}{V}$: density = mass / volume, in g/cm³ or kg/m³ (1 g/cm³ = 1,000 kg/m³). Example: 1,580 g / 200 cm³ = 7.9 g/cm³, typical of steel.

Stress $\sigma =\frac{F}{A}$ (force N / area mm², 1 N/mm² = 1 MPa). Strain $\epsilon =\frac{\Delta L}{L_0}$ (change in length / original length), a unitless ratio.

$E=\frac{\sigma }{\epsilon }$ in the elastic range. It measures stiffness (stress per unit strain), not breaking strength. Steel is about 200 GPa, aluminum about 70 GPa.

No. Hardness resists scratching and denting; toughness absorbs impact energy without cracking. A file or glass is hard but shatters; rubber is soft but tough. Scratch/wear means hardness, shock/blows means toughness.

Ductile: permanently stretched under tension, e.g. drawn into wire. Malleable: permanently flattened under compression, e.g. hammered or rolled into sheet or foil.

Fatigue: cracking from loads repeated many times, even below yield (bending a paper clip back and forth). Creep: slow ongoing deformation under a steady load over time (a plastic shelf sagging).

Hardening: heat then quench fast, making steel hard but brittle. Tempering: reheat to a lower temperature, trading some hardness for toughness. Annealing: heat and cool slowly to soften it.

When two different metals are electrically connected in an electrolyte such as salt water. The more active metal (zinc, aluminum) corrodes faster; the more noble one (copper, stainless) is protected.

No. At 2:1 the picture is twice actual size; at 1:2 it is half. The written dimension (e.g. 20 mm) is the true size regardless of scale, so never multiply a dimension by the scale.

Thick solid line: edge seen directly. Short dashes: edge hidden from that view. Long-short dash pattern: centerline marking an axis or symmetry, not solid material.

Four separate holes, each 6 mm in diameter, going all the way through. 4X is a count of features, not a multiplier on the diameter; hole locations come from separate dimensions.

Ø is diameter (full distance across through the center); R is radius (center to arc). $D=2R$, so Ø18 means R = 9 mm. Do not confuse Ø18 with R18.

$1\text{ in}=25.4\text{ mm}$ exactly. Multiply inches by 25.4 to get mm (2.50 in = 63.5 mm); divide mm by 25.4 for inches. Note 1/4 in = 6.35 mm, not 6 mm.

Bilateral ± varies both ways: 20.0 ± 0.2 means 19.8 to 20.2 mm. Unilateral varies one way: 12.00 +0.10/−0.00 means 12.00 to 12.10 mm. Endpoints are normally acceptable.

$P=\frac{1}{\text{TPI}}$. 1/4-20: 1/4 in major diameter, 20 threads per inch, so pitch 0.050 in. M8 × 1.25: 8 mm major diameter, 1.25 mm pitch.

Counterbore: flat-bottomed cylindrical recess around a hole, for socket-head screws. Countersink: cone-shaped entry so a flat-head screw sits flush. They are not interchangeable.

Elimination, substitution, engineering controls (guards, ventilation), administrative controls (training, procedures), then PPE. PPE protects only the wearer and never replaces guarding.

No. An e-stop halts motion but may not disconnect electrical, air, hydraulic, spring or gravity energy. Servicing requires lockout/tagout isolation and verification by an authorized person.

Lockout physically locks an energy-isolating device in the safe position. Tagout only attaches a warning tag and does not physically prevent operation; lockout is preferred whenever the device can be locked.

Work rest to wheel: at most 1/8 in (0.125 in). Upper tongue guard to wheel: at most 1/4 in (0.250 in). Do not swap them; a 3/16 in (0.1875 in) rest gap is too wide.

Clamp it in a vise or with clamps, never by hand or with a glove, so it cannot spin. Remove the chuck key before switching on so it is not thrown.

OSHA allows compressed-air cleaning only below 30 psi, with effective chip guarding and PPE. Never point air at skin, clothing or other people; a brush or chip hook is preferred.

Decibels are logarithmic: $\frac{I_2}{I_1}=10^{(L_2-L_1)/10}$. About +3 dB doubles sound intensity; +10 dB is ten times the intensity (80 to 90 dB). OSHA action level is 85 dBA over 8 hours.

Generally no. Gloves, loose sleeves, long hair and jewelry can be caught and pulled in by rotating parts. Secure clothing and hair and follow machine glove restrictions.