Combination Wrench
A two-ended open wrench with a box end to break fasteners loose and an open end to finish. Sized to the fastener.
What is it?
The combination wrench, also called an open-end or service wrench, has a closed box head at one end and an open head at the other. The open end slides over a fastener and turns it; the box end clamps the fastener to break it free or make a final snug. Most are sold in sets sized to common fastener heads.
What is it used for?
- Turning nuts and bolts
- Breaking seized fasteners loose with the box end
- Making a final snug without slipping
Common sizes
- SAE 3/8", 7/16", 1/2", 9/16"
- Metric 10, 11, 13, 14 mm
- Sets of 6 to 8 pieces
How to choose
Pick the wrench that exactly matches the fastener head size. Never step up a size, or you will round off the nut. A 6-8 piece set in one size system (SAE or metric) covers most repairs.
Anatomy
Understanding the parts of a combination wrench helps you use, maintain, and buy it with confidence.
- Open end: the U-shaped jaw that slides over a fastener
- Box end: the closed ring that grips a fastener on every side
- Jaws: the hardened gripping surfaces sized to the fastener head
Materials & construction
Wrenches are drop-forged from chrome-vanadium steel and heat-treated for strength, then chrome-plated to resist corrosion. The jaws are machined to a precise size so they grip fasteners without rounding them.
Safety & maintenance
- Match the wrench size exactly to the fastener to avoid rounding
- Pull the wrench rather than push when possible to avoid knuckle strikes
- Do not extend the wrench with a pipe for extra leverage on a fixed wrench
- Wipe oil from the jaws for a secure grip
Also known as
open-end wrench, box-end wrench