Wrench, Adjustable

Quick Answer: An adjustable wrench is a spanner with one fixed jaw and one movable jaw set by a knurled worm screw, so a single tool fits a range of nut and bolt sizes. It is used where carrying a full set of fixed spanners is impractical.

One Tool, Many Sizes

Turning the knurled worm moves the lower jaw along the head, opening or closing the gap. That flexibility means one tool can handle metric and inch fasteners, pipe fittings and odd sizes, which is why it is the tool most often found in a maintenance bag. The size is usually given by overall length, with longer wrenches opening wider and giving more leverage.

The trade-off is grip. There is always a little play in the movable jaw, so the tool is more likely to slip and round a nut than a well-fitting fixed spanner. Two habits reduce this: close the jaw firmly onto the flats before turning, and position the tool so the pulling force bears mainly on the fixed jaw. Where the size is known and the nut is tight, a fixed open jaw spanner or ring spanner is the better choice.

For gripping round pipes, which have no flats, a water pump plier or pipe wrench is used instead.

Specifications

Care & Handling

• Tighten the jaw onto the flats before every turn; do not leave a gap.
• Pull the handle so the load is on the fixed jaw, and pull rather than push.
• Do not use the wrench as a hammer or extend it with a pipe.
• Keep the worm screw clean and lightly oiled so it turns freely.

Applications

• General maintenance in laboratories, classrooms and workshops
• Tightening fittings on water taps, stills and equipment connections
• Assembling apparatus and furniture with mixed nut sizes
• Plumbing and fitting practicals in ITI and TVET courses

Why Choose LabEquip

Lab technicians, estate maintenance teams and technical institutes each keep a couple of these wrenches for quick jobs. LabEquip lists this tool in the General Lab Products range; send the lengths you need through the contact page.

Frequently Asked Questions

Which way should I pull an adjustable wrench?

Position it so the pulling force bears mainly on the fixed jaw, and pull towards you. This reduces the chance of the movable jaw opening and slipping.

Why does my adjustable wrench round off nuts?

The jaws were probably not closed tightly on the flats, or the load was on the movable jaw. Tighten the worm before each turn and reposition the tool.

Is an adjustable wrench as good as a fixed spanner?

It is more versatile but grips less securely. For tight or frequently used sizes, a correctly sized fixed spanner is better.

How are these wrenches sized?

Usually by overall length. A longer wrench opens wider and gives more leverage.

Can I use it on round pipes?

Not well; it needs flats to grip. Use a pipe wrench or water pump pliers for round pipe.

What maintenance does it need?

Clean grit out of the worm and jaw slot, add a drop of light oil and check that the movable jaw has not developed excessive play.

Last Updated: September 2026