How to Use Locking Pliers Properly (Grip, Adjust, Release)

Locking pliers work by clamping onto something and staying clamped, so the trick is setting the jaw width before you squeeze rather than after. You turn the knurled screw in the handle until the jaws almost close on the workpiece, then close the handles until the over-centre mechanism snaps shut. Get that adjustment right and the tool grips hard enough to turn a rounded bolt. Get it wrong and it either slips off or refuses to release.

What locking pliers actually do

Most people call them Mole grips or Vise-Grips, both of which are brand names for the same idea: a pair of pliers with an adjustable pivot and a toggle linkage. When the handles pass over centre, the linkage holds the jaws shut under load without you holding them. That is the whole point. Your hand is free, and the clamping force stays constant instead of fading as your grip tires.

That makes them three tools in one: a clamp for holding metal together while you drill, a gripper for fasteners a spanner can no longer bite, and an improvised handle for anything with a broken one.

Setting the jaws before you squeeze

This is the step people skip, and it is the step that decides whether the tool works. The adjusting screw at the end of the fixed handle changes how wide the jaws sit when the mechanism locks. Here is the sequence that works reliably:

1. Open the handles fully and back the adjusting screw out a few turns.
2. Place the jaws over the workpiece and hold them lightly closed against it.
3. Turn the adjusting screw in until it just stops turning easily with the jaws touching the work.
4. Open the handles, add roughly another half turn on the screw, then close the handles firmly.

You want a definite click and a noticeable resistance as the handles go over centre. If they close with no effort, the jaws are too wide and the pliers will spin off the moment you apply torque. If you cannot close them with normal hand pressure, back the screw off a quarter turn and try again. Forcing the handles shut on an over-tight setting is how you spring the frame or bend the adjusting screw.

Gripping a rounded or damaged fastener

Locking pliers are often the last resort before a nut splitter, so a bit of technique helps. Clamp across the flats, not the corners, and get as much jaw contact as you can. Curved jaw pliers with a wire cutter are the general purpose choice for round stock and hex heads. Long nose versions reach into recesses. Flat clamp style jaws are for sheet material and are poor at turning things.

Push the jaws right down onto the head so they are gripping the full depth rather than the top edge. Set them slightly tighter than you think you need. Then turn steadily rather than jerking, and keep the pliers square to the fastener so the load stays on the jaw faces. If the tool slips once, reset it tighter before trying again, because each slip polishes the fastener a little more and makes the next attempt harder.

On anything corroded, penetrating oil and twenty minutes of patience beat brute force every time.

Using them as a clamp

For clamping work the aim is different: enough force to hold parts still, not enough to mark them. Dial the adjustment back until the handles close with moderate effort, and on soft materials slip a scrap of leather or thin plywood between the jaws and the workpiece. The serrated teeth will happily emboss themselves into aluminium, brass and painted steel. If clamping is your main use, buy the deep throat C-clamp style, which spreads load over a wider pad and reaches further from the edge.

Releasing them without a fight

The release lever sits inside the moving handle. Pull it and the toggle passes back over centre, opening the jaws. If the pliers are clamped hard under load the lever can feel immovable, but do not attack it with a screwdriver. Squeeze the handles together very slightly first to take the strain off the linkage, then push the release and it usually pops straight away. On cheaper pliers where the lever has almost no leverage, backing the adjusting screw out a turn while still clamped normally frees things by hand.

Where not to use them

Locking pliers mark whatever they touch. On chrome taps, brake unions, alloy fittings and anything you intend to reuse and look at, reach for the correct spanner first. They also apply unpredictable force, so they are no substitute for a torque wrench on anything structural. If a job needs more leverage than the handles give you, the job needs a different tool.

Keeping them working

The pivot pins and the adjusting screw thread are the two things that seize. A drop of light oil on both a couple of times a year is enough, wiped off so it does not collect grit. A wire brush clears paint and rust from the teeth. Check the frame occasionally for any visible bend or opening at the jaws, because a sprung pair will never grip square again. Store them locked shut with the jaws almost closed, which protects the teeth from everything else in the drawer.