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Mole grips for a rounded nut

Updated: 21 October 2026

The spanner has already walked, the hex is shiny, and each slip is polishing what is left of the flats. Mole grips for a rounded nut are a last-resort bite, not a daily substitute for the right socket. You lock a 250 mm curved pair square and low, turn steadily, and stop after one slip instead of grinding the head into a bearing. This page starts from that failure. The scored table is on the [grip pliers comparison](/hub/pliers/grip-pliers). Listings were checked on 19 October 2026. We did not free a seized nut in a workshop. A qualifying purchase can earn a commission at no extra cost to you.

The spanner has already walked, the hex is shiny, and each slip is polishing what is left of the flats. Mole grips for a rounded nut are a last-resort bite, not a daily substitute for the right socket.

Our top picks

STANLEY Stanley FatMax locking mole grips 250 mm

Best overall

STANLEY Stanley FatMax locking mole grips 250 mm
9.0/10about £23.10
View offer
WORKPRO WORKPRO 3-piece locking pliers set

Best value

WORKPRO WORKPRO 3-piece locking pliers set
8.0/10about £21.99
View offer
Amtech Amtech 130 mm locking grip pliers

Alternative

Amtech Amtech 130 mm locking grip pliers
6.4/10about £4.95
View offer
On this page
  1. 1.When a locking plier is the right next tool
  2. 2.How to lock on without polishing the nut
  3. 3.Which pair in this set to reach for
  4. 4.When to stop

When a locking plier is the right next tool

A locking plier is the right next tool when the flats are damaged, an extractor is not in the box, and the teeth can still reach metal that has not gone fully round. Screwfix's mole-grips line still lists removing rounded nuts, and a third hand. That is not a promise the nut will come off. It is the wrong tool when flats remain. A six-point socket marks less. It is also the wrong tool if you are already thinking of a cheater pipe. Holding a pipe while you mark a cut is a clamp. Turning a rounded nut is torque, and the bite fails if you rock. A gas valve, a live conductor, or a safety-critical fastener is a competent person, not a tighter screw. The click itself is on how to use mole grips.

How to lock on without polishing the nut

Offer a curved jaw square and low, off the thread, so the teeth take the largest patch left. Clamp across the flats if any remain. A barrel head is a cylinder. Set the screw slightly tighter than a kiss, then click over centre. A lock that closes with no effort will polish the head. Turn steadily in the undo direction. Do not snatch, and do not saw the tool to find a bite. Each slip is a grinder. One slip, then stop. Reset on a fresh patch, or move to an extractor, a nut splitter, or a professional. A second slip on the same metal is how a nut becomes a stud you have to drill. Do not put a pipe on the handle.
STANLEY Stanley FatMax locking mole grips 250 mm

Testsieger

STANLEY Stanley FatMax locking mole grips 250 mm
9.0/10about £23.10
View offer

Which pair in this set to reach for

Reach for the Stanley FatMax 250 mm curved pair. UK reviews describe a hold on pipe, box and a strut shaft. One review finds more jaw play than a Milwaukee pair, so a click with a rocking head can be the jaws. Wipe factory grease first. There is no stated opening, so you offer the nut. If you already own the WORKPRO set, use the listed 250 mm curved piece, not the 180 mm curve or the 165 mm straight jaw. UK reviews mention wobble on the small pair and a frame that buckled on a snapped engine bolt. That is why this page will not recommend a cheater bar on that set. Put the Amtech down. Listed at 130 mm and 160 g, UK reviews say a stiff radiator valve barely turned and the jaws fell off a damaged screw. Who each listing is for sits on best mole grips.

When to stop

Stop after one polishing slip, if the frame flexes, if the lock will not hold, or if the next idea is a longer pipe. Wheel, steering, brake and structural fasteners are past a Saturday job once the head is gone. None of these three is marked to BS EN IEC 60900. Call a competent person for live work, a snapped stud in an engine or a pressure system, and a gas or heating valve that will not turn after a light attempt. If you do not yet own a 250 mm curved pair, the order of criteria is the buying guide.

Common questions

Can mole grips undo a rounded nut?
Sometimes. A 250 mm curved pair can be the last tool that still bites, if you set it tight, turn steadily, and stop after a slip. There is no promise the nut will come off. If the head is already a barrel, plan an extractor or a professional, not a longer pull.
Should I clamp on the flats or the corners?
On the flats if any flats remain, and as low as you can sit. Corners crush and then polish. If the head is fully round, you are gripping a cylinder. The curve still helps, but the chance of a clean turn is lower.
What size pair for a typical hex nut?
In this set, the 250 mm curved pair. That is the Stanley, or the large WORKPRO piece. The Amtech listed at 130 mm is the wrong starting size. None of the listings gives a clean jaw opening in millimetres, so you offer the nut rather than trusting a capacity table.
Why did they slip and make it worse?
The screw was too loose, the jaws were not square, or the head had already gone too far. Each slip is a grinder. Reset once. A second slip on the same metal is how you turn a nut into a stud that has to be drilled.
Can I put a pipe on the handle?
No. Extra leverage can dump the toggle and bend a light frame. One WORKPRO UK review already describes a buckle on a snapped engine bolt without adding a cheater. If you need that much force, the fastener is past this tool.
Will the Amtech 130 mm pair do it?
No, not as the first tool on seized or rounded work. UK reviews say the pair is smaller than it looks, that a stiff radiator valve barely turned, and that the jaws fell off a damaged screw. Keep it for a light hold in a small bag.
When do I stop and call a mechanic?
After one polishing slip, or sooner if the fastener is on brakes, steering, a wheel, a gas valve, a live conductor, or a snapped stud in an engine or pressure system. Holding a strut shaft is not a suspension repair. Prove dead before any electrical job. These three pairs are not insulated.

Related pages

Grip pliers

Best mole grips UK: top pick, set, or a pocket pair

Mole grips buying guide: jaw, length and lock first

Curved vs straight jaw locking pliers, which to buy

How to use mole grips: set, lock, and then release

Sources

Public UK sources from the research digest, last checked on 19 October 2026. Shelf prices and star lines are the amazon.co.uk figures in the display file.

  1. Stanley FatMax locking mole grips, amazon.co.uk B01MQK1HT7 (retrieved 19 October 2026)
  2. WORKPRO 3-piece locking pliers set, amazon.co.uk B01KZM2R4O (retrieved 19 October 2026)
  3. Amtech 130 mm locking grip pliers, amazon.co.uk B009DNBIKG (retrieved 19 October 2026)
  4. Wonkee Donkee Tools: which type of mole grips (retrieved 19 October 2026)
  5. HSE: PUWER overview (retrieved 19 October 2026)
  6. BSI: BS EN IEC 60900:2018 (retrieved 19 October 2026)
  7. Screwfix: pliers buying guide (retrieved 19 October 2026)
  8. B&Q: mole grips (retrieved 19 October 2026)