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How to use an adjustable spanner without rounding the flats

Updated: 22 October 2026

The wing-mirror nut is still hexagonal, and the adjustable spanner has already skated once. How to use an adjustable spanner, with the tool already in the drawer, means seating both jaws, pulling so the fixed jaw takes the load, and stopping when the head rocks or you want a tube for more force. Which length to own sits on the [adjustable spanner comparison](/hub/hand-tools/adjustable-spanner) and the [adjustable spanner buying guide](/hub/hand-tools/adjustable-spanner/sub/adjustable-spanner-buying-guide). A qualifying purchase can earn us a commission at no extra cost to you. Peter F. set this method out in October 2026 from public use guides and amazon.co.uk review patterns. It is not a lab test.

The wing-mirror nut is still hexagonal, and the adjustable spanner has already skated once.

Our top picks

Bahco Bahco 80 series 3-piece set

Best overall

Bahco Bahco 80 series 3-piece set
8.6/10about £39.99
View offer
Stanley Stanley 150 mm adjustable wrench

Rank 2

Stanley Stanley 150 mm adjustable wrench
7.0/10about £9.24
View offer
WORKPRO WORKPRO 200 mm pipe-jaw wrench

Rank 3

WORKPRO WORKPRO 200 mm pipe-jaw wrench
5.7/10about £12.99
View offer
On this page
  1. 1.Set the jaws on the flats
  2. 2.Put the load on the fixed jaw
  3. 3.Re-check the worm as you go
  4. 4.What you do not add to the handle

Set the jaws on the flats

An adjustable spanner grips two opposite flats. If the opening is a shade wide, the jaws rest on the corners, and the first serious pull shears those corners off. Wind the movable jaw in until both faces touch the flats, then try to rock the head. BuildWiz treats that rock as the check before any load. Close the jaw until the rock disappears. Further turns only crowd the worm. When you can already see a bright crescent, move to a ring or a socket. That choice is on the adjustable spanner vs combination spanner page.

Put the load on the fixed jaw

The fixed jaw is the solid one, part of the head. The movable jaw is the one the worm slides. Turn the spanner so a pull towards you presses the nut against the fixed jaw. RIDGID's use guide tells you to pull the handle towards you. BuildWiz puts the force on the fixed jaw. A paragraph that says to pull towards the movable jaw drives the nut into the jaw the worm is holding, the head spreads, and the flats round. If the sliding jaw is the one being crushed, flip the tool. A push sends your knuckles into the bracket when the nut frees. WORKPRO includes a toothed jaw. Teeth belong on round stock or a fastener past saving, and they mark chrome and brass. A hex that still has corners takes the smooth side.
Bahco Bahco 80 series 3-piece set

Testsieger

Bahco Bahco 80 series 3-piece set
8.6/10about £39.99
View offer

Re-check the worm as you go

Review patterns on this amazon.co.uk set describe jaws that open in use on Navegando, Shall, WORKPRO, the Stanley 0-90-947, Amazon Basics and LSLANSOON. The worm walks back a fraction each time the load comes off and on again. After a few swings the jaws sit on the corners. Lift the spanner clear, wind the worm until the head will not rock, and only then pull. Do that each time you reposition. A tool that still creeps open is the wrong one for a nut you cannot afford to damage. These listings have not been checked against ISO 6787:2018 in a lab, so the rock in your hand is the test on the day. On a compression joint, the second spanner belongs on the adjustable spanner for plumbing page, which is also where gas work leaves the household toolbox.

What you do not add to the handle

A pipe on the handle multiplies the force past the jaw and the worm. The head springs and the gap grows. RIDGID's guide rules out an extension, a hammer blow, and a bent handle left in service. If the nut will not move on the bare handle, change to a fixed spanner or a socket. At work, the Health and Safety Executive's PUWER overview requires equipment to be suitable and maintained. A jaw that rocks, a bent handle, or a worm that will not hold a setting comes out of service. If the joint is on the gas side, stop and call a Gas Safe registered engineer.

Common questions

Which jaw should take the load?
The fixed jaw, the solid one that does not slide on the worm. Turn the spanner so a pull towards you presses the nut into that jaw. The movable jaw then only keeps the gap. If the head can still rock, neither jaw is seated, and the corners will go before the nut turns.
How tight should the worm be before you pull?
Wind it until both jaws sit on the flats and the head will not rock. That is tight enough. Extra turns only load the screw thread. Reviews of the Stanley 0-90-947, WORKPRO and Amazon Basics describe the jaw opening while the nut is still turning, so a setting that felt firm can be loose a few swings later.
Why does the setting creep after a few turns?
The worm walks back when the load cycles, so a gap that was snug on the first flat is wide by the third. Lift the spanner off, close the jaw until the rock stops, and pull again. If it still creeps, finish with a ring or a socket.
Do you pull or push an adjustable wrench?
Pull towards you, with the fixed jaw taking the load. RIDGID's use guide prefers a pull. A push drives your hand into the bracket when the nut breaks free. If the space only allows a push, keep the same jaw orientation and use a shorter stroke.
Can you put a pipe on the handle or hit it with a hammer?
Leave the handle bare. A tube, and a hammer on the handle, overload the jaw and the worm. The head springs and the opening grows. RIDGID also says to take a bent handle out of service. If a pull on the handle alone will not move the nut, change to a fixed spanner or a socket.
When do serrated jaws belong, and what do they do to chrome?
Teeth belong on round stock or on a fastener that is already past saving. They mark chrome, brass and plate, which is the limit RIDGID states for a serrated reversible jaw. Use the smooth jaw on a hex that still has corners. If the corners are already round, teeth may bite, and they will scar the surface while they do it.

Related pages

Best adjustable spanner

Adjustable spanner

Adjustable spanner size: opening before the length

Adjustable spanner for plumbing on 15 mm and 22 mm

Adjustable spanner vs combination spanner, when to switch

Sources

Public UK sources listed in the research digest for this comparison. Shelf prices and star lines are the amazon.co.uk figures in the product display.

  1. ISO 6787:2018, adjustable wrenches (retrieved 22 October 2026)
  2. BS ISO 6787:2018 (retrieved 22 October 2026)
  3. HSE: Provision and Use of Work Equipment Regulations (PUWER) (retrieved 22 October 2026)
  4. Gas Safety (Installation and Use) Regulations 1998, regulation 3 (retrieved 22 October 2026)
  5. Gas Safe Register: home improvements (retrieved 22 October 2026)
  6. Consumer Rights Act 2015, section 22 (retrieved 22 October 2026)
  7. Consumer Rights Act 2015, section 9 (retrieved 22 October 2026)
  8. BuildWiz: adjustable wrench (trade guide) (retrieved 22 October 2026)