Combination Wrench

What Is a Combination Wrench?

A combination wrench is a fixed-size wrench with two different ends: an open end for quick engagement and a box end (a closed, ring-shaped head) for maximum grip. Both ends fit the same fastener size. Most have a slight angle (often 15°) on the open end and an offset box end to help clear obstacles and work in tight spaces.

How It Works

Open end: The U-shaped jaw slips onto two flat sides of a nut or bolt head. It’s fast to place and handy when there’s not enough room to slip a ring over the fastener. Because it contacts fewer faces, it can slip more easily under heavy load.
Box end: The ring typically has 12 points (sometimes 6). It fully surrounds the fastener for better grip and less chance of rounding. The 12-point style engages more positions, so you can turn fasteners with a smaller swing arc. A 6-point box end grips more of the flats and is kinder to stubborn fasteners.

The ends are the same size, so you can start with the open end for speed and switch to the box end for final tightening or loosening.

Common DIY Uses

Automotive and bikes: Loosening 10 mm battery clamps, 13 mm body fasteners, or 15 mm axle nuts on bicycles.
Appliances and furniture: Tightening bed frame bolts, appliance brackets, and hardware on garage door openers.
Plumbing and HVAC: Holding a hex fitting while you loosen another component (use a flare-nut wrench directly on tubing nuts).
Outdoor power equipment: Servicing mower handles or shields where sockets won’t fit.

Any project with hex-head or square fasteners is a candidate for a combination wrench.

Types and Variations

Standard vs. stubby: Stubby wrenches are shorter for cramped spaces. Standard lengths provide more leverage.
Long-handle (extra reach): Longer handle increases leverage for stubborn fasteners but raises the risk of over-tightening.
Ratcheting box end: The box end has an internal ratchet, letting you turn without lifting and repositioning. Great in confined areas. Use caution when breaking free stuck fasteners.
Flex-head: The box end pivots to reach awkward angles around obstructions.
6-point vs. 12-point box end: 6-point provides stronger contact on the flats; 12-point offers more indexing positions in tight spaces.
Finishes and materials: Chrome vanadium steel with polished chrome resists corrosion and wipes clean. Black oxide or phosphate finishes reduce glare and can improve grip when oily.
SAE vs. metric: SAE sizes are in inches (e.g., 7/16 in., 1/2 in.). Metric sizes are in millimeters (e.g., 10 mm, 13 mm). Many households benefit from owning both.

How to Choose the Right One

Start with a core set: Metric 8–19 mm and SAE 1/4–1 in. cover most household and automotive tasks. If budget is tight, pick sizes you encounter most (10, 12, 13, 14, 15, 17 mm; 3/8, 7/16, 1/2, 9/16 in.).
Check size markings: Large, stamped or laser-etched markings are easier to read in dim spaces.
Prefer a 15° open-end angle and box-end offset: Lets you flip the wrench for a new bite in tight quarters.
Consider ratcheting for frequent work: Speeds up repetitive tasks; keep a standard box end for heavy breakaway torque.
Look for quality fit and finish: Crisp jaws, smooth ratchet action (if applicable), and a comfortable handle reduce fatigue and slip risk.
Match system to fasteners: Don’t mix metric on SAE hardware or vice versa—sizes that are “close” can round bolts.

Using It Safely and Effectively

Try the box end first: It grips more faces and reduces rounding, especially on tight or rusty fasteners.
Pull, don’t push: Pulling keeps your knuckles clear if the wrench slips. If you must push, use an open palm.
Keep it square: Align the wrench so force is applied straight along the flats, not at an angle.
Flip for a new bite: The 15° offsets let you flip the wrench to index in confined spaces.
Break loose smartly: Apply penetrating oil, tap the head lightly to help it wick in, and use the non-ratcheting box end for the first movement.
Avoid cheater bars: Overloading can damage the wrench or fastener. If more torque is needed, step up to a longer wrench rated for the job or use a breaker bar with a socket.
Finish with proper torque: For critical parts (brakes, engine components), use a torque wrench and sockets for final tightening.

Maintenance and Care

Wipe after use: Remove grime and moisture to prevent corrosion and improve grip next time.
Light oil film: A quick pass with a rust inhibitor or light oil helps in humid garages.
Store by size: A wrench rack or roll keeps sizes organized and prevents loss.
Inspect jaws and ratchets: Replace wrenches with spread or chipped jaws; service or replace ratcheting mechanisms that skip under load.
No hammering: Don’t strike a standard wrench with a hammer unless it’s a slugging wrench designed for that purpose.

Common Mistakes to Avoid

Using the open end on stuck fasteners: Increases the chance of rounding. Use the box end or a socket.
Mixing SAE and metric: “Close” isn’t good enough—use the exact size.
Hitting the wrench with a hammer: Can crack the tool or damage the fastener.
Using a ratcheting end to break loose: Ratchets are for speed, not heavy breakaway torque (unless specifically rated).
Using the wrench as a pry bar: Can bend or weaken it.
Working on flare nuts with a standard open end: Use a flare‑nut wrench to avoid crushing the nut.

Related Terms

Open-end wrench: Only the U-shaped jaw; faster placement, less grip.
Box-end wrench: Only the ring end; maximum grip on fasteners.
Ratcheting wrench: Combination wrench with a ratcheting box end.
Socket wrench (ratchet): Uses interchangeable sockets; good for high torque and speed.
Torque wrench: Tightens fasteners to a specific torque value.
Flare-nut wrench (line wrench): For tubing nuts on plumbing or brake lines.
Spanner: Another term for wrench, commonly used outside North America.

Practical Examples

Swap a car battery: Use a 10 mm combination wrench. Break loose the clamp bolt with the box end, then spin it off with the open end. Remove the negative terminal first to avoid shorts.
Tighten a wobbly bed frame: If the hardware is 13 mm, start each bolt with the open end where space is tight near slats, then switch to the box end for final snugging.
Adjust a bicycle with axle nuts: A 15 mm combination wrench loosens the axle nuts to remove a wheel on bikes without quick releases. Use the box end to avoid slipping.
Replace a dishwasher mounting bracket: Hold the bracket bolt with a 10 mm box end while you tighten the nut beneath with a socket. The open end helps position the bolt in a narrow gap.
Secure mower handle bolts: Use the box end on the bolt head and an adjustable or second wrench on the nut, keeping the tool square to avoid rounding.

With a small set of metric and SAE combination wrenches, most household and garage fasteners are within reach. Use the box end whenever possible, keep sizes organized, and you’ll work faster with fewer rounded bolts.