Power Tool Glossary
109 terms defined in plain language. No jargon-to-jargon definitions.
A
Accuracy Rating
Accuracy rating tells you how far off a measuring tool can be from the true value, expressed as a tolerance. A laser level rated at plus or minus 1/8-inch at...
AFCI (Arc-Fault Circuit Interrupter)
An AFCI breaker detects electrical arcs, the sparking that happens when a wire is damaged, a connection is loose, or a nail has pierced a cable inside a wall...
Amp-Hours (Ah)
Amp-hours measure a battery's capacity, or how much energy it can store. A 2.0Ah battery can deliver 2 amps for one hour, or 4 amps for 30 minutes, or 1 amp ...
Amps (Amperage)
Amps measure the electrical current a corded tool draws from the wall. A higher amp rating generally means a more powerful motor. A 7-amp circular saw is a l...
Anti-Vibration
Anti-vibration features reduce the vibration transmitted from the tool to your hand. Sanders and grinders are the biggest culprits. A random-orbit sander vib...
Anvil
In an impact driver or impact wrench, the anvil is the output shaft that receives the hammer strikes and transfers them to the bit or socket. The hammer spin...
Arbor Size
The arbor is the shaft that the blade mounts onto. Arbor size is the diameter of the hole in the center of the blade. Most 7-1/4-inch circular saw blades use...
Arbor Thread
The arbor thread is the threaded spindle on the grinder where the wheel mounts. Most 4-1/2 and 5-inch angle grinders use a 5/8-11 UNC thread (5/8-inch diamet...
B
Belt Clip
A belt clip is a stamped or molded metal hook on the side or bottom of a cordless tool that hooks over your belt or tool pouch. Most impact drivers and compa...
Bench Grinder
A bench grinder is a stationary tool with two grinding wheels mounted on opposite ends of a motor shaft. It bolts to a workbench. One wheel is usually coarse...
Bevel Cut
A bevel cut angles the blade relative to the face of the material. Instead of cutting straight through at 90 degrees, the saw tilts to 15, 22.5, 30, or 45 de...
Bevel Joint
A bevel joint is formed when the edge of a board is cut at an angle other than 90 degrees through its thickness. Two boards beveled at complementary angles c...
Blade Clamp
A blade clamp is the mechanism that holds and releases the blade in a reciprocating saw or jigsaw. Modern recip saws use a tool-free blade clamp: you twist a...
Blade Guard
The blade guard is the spring-loaded cover that shields the exposed part of the blade when you're not cutting. On a circular saw, the lower guard retracts as...
Blade Kerf
Kerf is the width of the cut a blade makes, measured in fractions of an inch. A standard full-kerf circular saw blade cuts about 1/8-inch (0.125") wide. A th...
Brad Nailer
A brad nailer drives 18-gauge brad nails, which are thin, small-headed fasteners used for trim, molding, and light assembly. Brad nails are 5/8-inch to 2 inc...
Breakaway Torque
Breakaway torque is the peak torque the tool delivers in its initial burst to crack a stuck fastener loose. It's different from the continuous torque rating,...
Brushless Motor
A brushless motor uses electronic commutation instead of physical carbon brushes to switch the magnetic field. No brushes means no friction from contact, les...
C
Carbide-Tipped
Carbide-tipped means small pieces of tungsten carbide are brazed onto the cutting edges of a steel tool body. Tungsten carbide is much harder than steel and ...
Cement Board
Cement board is a sheet material made from Portland cement and reinforcing fibers (fiberglass or cellulose), sold under brands like Hardie Backer, Durock, an...
CFM (Cubic Feet Per Minute)
CFM measures airflow volume, the amount of air a dust collector, blower, or vacuum moves per minute. A shop vacuum pulls 100 to 150 CFM. A single-stage dust ...
Chuck Size
The chuck is the clamp at the front of the drill that grips the bit. Chuck size tells you the largest bit shank the tool accepts. Most cordless drills use a ...
Click Torque Wrench
A click torque wrench is a manual wrench with an adjustable torque setting. You dial in the target ft-lbs or Nm on the handle, then tighten the fastener. Whe...
Clutch Settings
The clutch is the numbered ring behind the chuck on a drill-driver. It sets a torque limit. When the tool hits that resistance level, the clutch slips and th...
Collet
A collet is a slotted sleeve that grips a tool shank by compressing around it when a nut is tightened. Routers use collets to hold bits (1/4-inch and 1/2-inc...
Corded vs. Cordless
Corded tools plug into a wall outlet and draw 120V (in North America) through a power cord. Cordless tools run on rechargeable lithium-ion battery packs, typ...
Countersink
A countersink is a conical recess cut into the surface of a board so a flat-head screw sits flush with or below the surface. A countersink bit has a tapered ...
Crosscut
A crosscut goes across the width of a board, perpendicular to the grain. Cutting a 2x4 to length is a crosscut. Trimming the end off a shelf board is a cross...
D
Dado
A dado is a flat-bottomed groove cut across the grain of a board. It's sized to accept another board's thickness, creating a strong shelf or divider joint. Y...
Dado Set (Stacked)
A stacked dado set is a collection of blades that mount on a table saw arbor to cut flat-bottomed grooves (dados) in a single pass. The set includes two oute...
Depth Stop
A depth stop limits how far a drill bit, router bit, or saw blade can travel into the material. On a drill, it's a collar that clamps onto the bit at a set d...
Drill-Driver
A drill-driver combines drilling (boring holes) and driving (fastening screws) in one tool. It has a keyless chuck, a clutch ring, and usually two speed rang...
Drive Size
Drive size is the square nub on the wrench or ratchet where the socket attaches. Common sizes are 1/4-inch, 3/8-inch, and 1/2-inch. The size determines what ...
Dust Collection
Dust collection on a sander is the system that captures wood particles as you sand. Most random-orbit sanders have built-in dust ports that connect to a vacu...
Dust Mask vs. Respirator
A dust mask is a disposable paper or fabric filter that covers the nose and mouth. It blocks large particles like sawdust and drywall dust. An N95 mask filte...
E
F
Fast Charger
A fast charger replenishes a cordless tool battery at an accelerated rate compared to the standard charger included with most kits. Standard chargers take 60...
Flange Nut
The flange nut is the fastener that locks the wheel onto the grinder's spindle. A standard angle grinder has an inner flange (fixed to the spindle) and an ou...
Foot-Pounds (ft-lbs)
Foot-pounds measure torque on larger fasteners, typically in automotive and structural work. One foot-pound is the force of one pound applied at the end of a...
Forstner Bit
A Forstner bit cuts flat-bottomed holes with clean, chip-free edges. The cutting action comes from a rim cutter around the outside and a center spur that kee...
G
GFCI (Ground-Fault Circuit Interrupter)
A GFCI monitors the current flowing out on the hot wire and returning on the neutral wire. If it detects an imbalance of 4 to 6 milliamps, it trips in about ...
Grinding Wheel Speed (SFM)
Grinding wheel speed is how fast the edge of the disc moves, measured in surface feet per minute (SFM) or meters per second. It's a function of both RPM and ...
Grit Rating
Grit rating is the number of abrasive particles per square inch on a sheet of sandpaper. Lower numbers mean coarser, more aggressive abrasive. Higher numbers...
H
Hammer Action
Hammer action adds a rapid forward-and-back pulsing to the drill's rotation. The bit spins and hammers simultaneously, pulverizing masonry while the rotation...
Header
A header is a horizontal beam above a window or door opening in a framed wall. It carries the load from above the opening and transfers it to the studs on ei...
HEPA Filter
HEPA stands for High Efficiency Particulate Air. A true HEPA filter captures 99.97% of particles 0.3 microns and larger. For context, fine wood dust is 1 to ...
Hex Shank
A hex shank is a six-sided bit shank, usually 1/4-inch across the flats. Impact drivers use a 1/4-inch hex collet instead of a traditional chuck, so they onl...
Hole Saw
A hole saw is a cylindrical saw blade with teeth on the rim, mounted on a mandrel (arbor) that fits in a drill chuck. The center pilot bit keeps the saw trac...
Hook-and-Loop
Hook-and-loop is the attachment system that holds sanding discs to the pad. It's the same concept as Velcro: tiny hooks on the pad grip loops on the back of ...
I
Impact Wrench
An impact wrench uses the same hammer-and-anvil mechanism as an impact driver but with a square drive (1/4, 3/8, or 1/2-inch) instead of a hex collet. It's d...
IPM (Impacts Per Minute)
IPM counts how many axial strikes the mechanism delivers per minute. At 3,500 IPM, the tool hammers the anvil 3,500 times in 60 seconds. Each strike advances...
J
K
Keyed Chuck
A keyed chuck uses a small T-handled gear key that meshes with teeth on the chuck ring. You insert the key into one of three holes on the chuck body and turn...
Keyless Chuck
A keyless chuck tightens and loosens by hand. You grip the outer sleeve, hold the tool body, and twist. Three jaws inside close around the bit shank. Every m...
Kickback
Kickback happens when a spinning blade or disc catches the workpiece and throws it back at the operator. On a table saw, kickback occurs when the wood pinche...
L
Laser Class
Laser class rates the potential hazard of the laser beam to your eyes. Construction lasers are Class 2 (up to 1 mW) or Class 3R (up to 5 mW). Class 2 lasers ...
LED Work Light
An LED work light on a cordless tool is a small diode near the chuck or blade that illuminates the work surface when you pull the trigger. Most modern drills...
Load-Bearing Wall
A load-bearing wall carries weight from the structure above it down to the foundation. Exterior walls are almost always load-bearing. Interior walls that run...
M
MDF (Medium-Density Fiberboard)
MDF is an engineered wood panel made from wood fibers bonded with resin under heat and pressure. It comes in 4x8-foot sheets, typically 1/2-inch or 3/4-inch ...
Miter Angle
The miter angle is the rotation of the blade relative to the fence, cutting across the width of the board. A 0-degree miter is a straight crosscut. A 45-degr...
Miter Joint
A miter joint is formed when two pieces are cut at equal angles (usually 45 degrees each) and joined to make a corner, typically 90 degrees. Picture frames, ...
N
NEC (National Electrical Code)
The NEC is the standard for safe electrical installation in the United States, published by the National Fire Protection Association (NFPA) and updated every...
Newton-Meters (Nm)
Newton-meters measure torque in the metric system. One Newton-meter is the force of one Newton applied at the end of a one-meter lever arm. European and Asia...
No-Load Speed
No-load speed is the RPM the tool reaches with nothing resisting the motor. It's measured with the bit or blade spinning freely in the air. Every tool spec s...
NRR (Noise Reduction Rating)
NRR is a number printed on hearing protection that tells you how many decibels it blocks under lab conditions. A rating of NRR 25 means the protector reduces...
O
On Center (OC)
On center (abbreviated OC or o.c.) is a framing measurement taken from the center of one stud or joist to the center of the next. 16 inches on center means t...
Orbital Action (Jigsaw)
Orbital action on a jigsaw adds a forward-and-back motion to the blade's up-and-down stroke. Instead of moving straight up and down, the blade swings forward...
Orbits Per Minute (OPM)
OPM is the number of small circular orbits the sanding pad completes per minute. A random-orbit sander rated at 12,000 OPM moves the pad in 12,000 tiny circl...
OSB (Oriented Strand Board)
OSB is an engineered wood panel made from compressed wood strands arranged in layers, with each layer oriented perpendicular to the one below it. This cross-...
Oscillating Multi-Tool
An oscillating multi-tool vibrates a blade or pad in a tight arc (about 3 degrees) at 10,000 to 20,000 oscillations per minute. It doesn't spin. That oscilla...
P
PEX (Cross-Linked Polyethylene)
PEX is a flexible plastic tubing used for residential water supply lines. It bends around corners without fittings, resists freezing better than copper (it e...
Pilot Hole
A pilot hole is a small-diameter hole drilled before driving a screw. The hole should match the screw's root diameter (the shaft minus the threads) so the th...
Plunge Cut
A plunge cut starts in the middle of a workpiece instead of from an edge. With a circular saw, you retract the blade guard, rest the front of the baseplate o...
Pocket Hole
A pocket hole is an angled hole drilled into one workpiece that accepts a self-tapping screw to join it to another piece. The hole is drilled at about 15 deg...
Pressure-Treated Lumber
Pressure-treated (PT) lumber is wood that has been infused with chemical preservatives under pressure to resist rot, insects, and fungal decay. The treatment...
PSA (Pressure-Sensitive Adhesive)
PSA sanding discs have a peel-and-stick adhesive backing, like a giant sticker. You peel the paper off, press the disc onto the sanding pad, and it stays put...
Q
R
Rabbet
A rabbet is a step-shaped cut along the edge or end of a board. It removes a rectangular section, leaving an L-shaped profile. Rabbets are used to join the b...
Rafter Hook
A rafter hook is a retractable metal clip on a drill or impact driver that lets you hang the tool from a belt, rafter, joist, or scaffold rail. Most pro-grad...
Random Orbit
Random orbit means the sanding pad spins and orbits simultaneously in an irregular pattern. The pad rotates on its center axis while also moving in small ell...
Ratcheting Mechanism
The ratcheting mechanism is a toothed gear inside the wrench head that allows rotation in one direction while freefheeling in the other. A 72-tooth ratchet m...
Rip Capacity
Rip capacity is the maximum width of material a table saw can cut between the blade and the fence. A contractor saw with 24-1/2-inch rip capacity handles a f...
Rip Cut
A rip cut runs along the length of a board, parallel to the grain. Ripping is how you make a 2x6 into a narrower strip, or cut a sheet of plywood to a specif...
Riving Knife
A riving knife is a curved piece of steel mounted directly behind the table saw blade, rising and falling with it. It sits in the kerf (the slot the blade cu...
Romex (NM-B Cable)
Romex is the brand name for non-metallic sheathed cable (NM-B), the standard wiring for residential circuits in the US. The outer jacket is a flat, usually w...
Rotary Hammer
A rotary hammer uses a piston-driven mechanism to deliver heavy blows along the bit axis while simultaneously rotating. It hits much harder than a hammer dri...
RPM (Rotations Per Minute)
RPM is how fast the chuck spins. A 3,600 RPM drill rotates 3,600 times per minute at full speed with no load. On soft materials like drywall or pine, higher ...
S
Sanding Pad Size
Pad size is the diameter of the sanding disc the tool accepts. The standard is 5 inches (125 mm) for random-orbit sanders. Some models use 6-inch pads, which...
SDS-Plus
SDS-Plus is a bit retention system used on rotary hammers. The shank has two open grooves and two closed grooves that lock into the chuck with a twist, no ti...
Self-Leveling
A self-leveling laser uses an internal pendulum or gimbal to automatically find true level within a range of about 4 degrees. Set the tool on a surface that'...
Sheathing
Sheathing is the layer of sheet material fastened to the outside of wall studs or the top of floor joists. Wall sheathing is usually 7/16-inch or 1/2-inch OS...
Side Handle
A side handle is an auxiliary grip that screws into the collar behind the chuck on a drill or bolts onto the body of an angle grinder. It gives you a second ...
Soft Start
Soft start is an electronic feature that ramps the motor up to full speed gradually instead of hitting full RPM the instant you pull the trigger. The ramp ta...
Spade Bit
A spade bit (also called a paddle bit) is a flat steel blade with a center point, designed for fast rough holes in wood. Common sizes go from 3/8-inch to 1-1...
SPM (Strokes Per Minute)
SPM counts the number of full back-and-forth blade strokes a reciprocating saw or jigsaw makes per minute. A reciprocating saw at 3,000 SPM pushes the blade ...
Stud
A stud is a vertical framing member in a wall, typically a 2x4 or 2x6 standing on its narrow edge. Studs run from the bottom plate (sill plate) to the top pl...
Stud Finder Modes
Modern stud finders have multiple detection modes for different materials behind the wall. Stud mode detects the density change at wood or metal framing, typ...
T
Teeth Per Inch (TPI)
TPI counts the number of teeth in one inch of blade length. Reciprocating saw and jigsaw blades are spec'd in TPI rather than total tooth count. Low TPI (3 t...
Tooth Count
Tooth count is the total number of teeth on a circular saw, miter saw, or table saw blade. A 24-tooth blade cuts fast and rough. A 40-tooth blade is a good g...
Torque (in-lbs)
Torque measures rotational force in inch-pounds. A drill rated at 2,000 in-lbs applies 2,000 pounds of twisting force across a 1-inch lever arm. Higher torqu...
Track Saw
A track saw (also called a plunge saw) is a circular saw that rides on an aluminum guide rail. The saw body clips onto the rail and slides along it, making p...
Trigger Lock
A trigger lock holds the trigger in the on position so you don't have to squeeze continuously. On a corded drill, it's a button near the trigger that clicks ...
U
V
Variable Speed
Variable speed lets you control the tool's RPM, either with a trigger that responds to finger pressure or a dial that sets a maximum speed. Trigger-based var...
Voltage Drop
Voltage drop is the loss of electrical pressure (voltage) that occurs as current flows through a wire over distance. Every wire has resistance, and that resi...
W
Watt-Hours (Wh)
Watt-hours combine voltage and amp-hours into a single energy number. The formula is simple: voltage times amp-hours equals watt-hours. A 20V 5.0Ah battery s...
Wheel Diameter
Wheel diameter is the size of the grinding, cutting, or flap disc the tool accepts. The most common size for handheld angle grinders is 4-1/2 inches (115 mm)...
Wire Gauge (AWG)
Wire gauge measures the diameter of an electrical conductor using the American Wire Gauge (AWG) system. The scale runs backward: lower numbers mean thicker w...
Worm Drive
A worm-drive circular saw uses a worm gear set where the motor sits behind the blade instead of beside it. This puts the blade on the left side of the saw, g...