Holding it square
Steel moves as it cools, and what holds it decides whether the assembly is square afterwards. We compare bench vices, welding clamps, magnetic squares and slotted fixture tables — on capacity, rigidity and how much they give when the weld shrinks.
Six magnets for €20: they hold a corner square while you tack, and they are not clamps.
Best for: Holding a frame square long enough to tack it
Nearly double the hold of the cheap sets — which changes what section they can position.
Best for: Positioning heavier box section and plate before tacking
A vice that drops into a 16 mm (0.63 in) fixture-table hole — clamping where the work is, not at the bench edge.
Best for: Owners of a fixture table who need to grip rather than just clamp down
An adapter that puts a proper German bench vice onto a fixture table — keeping the vice you already own.
Best for: Anyone with a good bench vice and a new fixture table
A magnet with an off switch — which is what makes a strong magnet usable rather than a nuisance.
Best for: Repeated fabrication where fixed magnets are too weak and too hard to remove
The only clamp in this hub whose entire specification is figures — capacity, throat, length and thread, with nothing else claimed.
Best for: Tube and exhaust work, where the pliers have to sit on a round section and stay there
Three big locking clamps that publish both the figures that matter — a 7.8 in throat and a 6.3 in opening, the deepest and widest in this hub.
Best for: Clamping a plate or a frame well in from the edge, where a short-throat clamp cannot reach the seam
A set of 6-inch locking clamps whose own listing cannot agree on how many are in the box.
Best for: Small work and body panels, where several modest clamps beat one large one
A V-jaw clamp that publishes the tube sizes it holds and states plainly that it takes square section as well as round.
Best for: Frames mixing round and square tube, where one clamp has to seat on both
The only clamp on this shelf that holds a right angle on its own, bolted to a bench — with a copper-plated screw so spatter does not weld to the thread.
Best for: Repeating the same square corner, where the clamp sets the angle instead of a magnet suggesting it
A pipe alignment clamp whose five bullets contain no capacity, no weight, no dimension and no material grade — on the highest price in the American half of this hub.
Best for: Pipe butt welds, if you can establish from the seller which diameters it fits
The only vise in this hub that publishes all three of the figures that decide whether a part will fit in it — opening, jaw width and its own weight.
Best for: Holding a part square under a drill press, where the alternative is a hand and hope
Four quick-release clamps that publish what no other clamp in this hub publishes — a holding force, and every dimension needed to drill the mounting holes.
Best for: Building a jig or a fixture, where the clamp is screwed down once and used a thousand times
Mass and the quality of the screw decide what a vice can grip without developing play. It is a purchase made once.
Clamps and magnetic squares are often enough to position two parts long enough to tack them.
Mass is what absorbs the blows and prevents play. A light vice backs away or twists as soon as you file or strike.
With soft aluminum or copper jaw covers over the serrated jaws. It is a simple accessory you can also make yourself.
They position long enough for a tack, no more. Moderate force makes them let go.
On the anvil section provided, yes; on the jaws or the body, never. A cast-iron vice cracks under badly placed blows.
With V-jaws, or by sliding an offcut of tube inside to stop it going oval.
A little grease on the screw and nut markedly extends a vice’s life. Chips and filings are its main enemies.
The jaws should be flush with or slightly past the edge, so a long piece can be gripped vertically.
Locking pliers go on one-handed and grip hard over a small area; clamps spread the load better and need two hands.
Mass makes the vice: a light model backs away as soon as you file. Strike only on the anvil section, never on the jaws, protect visible parts with soft jaws — and know that magnetic squares position without ever holding.
There is no table here, and the reason is in the listings. The figure published most often across these 13 products is hold, given by 2 of them — short of the four in five a column needs to compare rather than to display gaps. Each product page says what its own maker published.
$19 – $31
3 models
POWERTEC 20326, Type-225D toggle clamps, 4-pack, Strong Hand Tools PG114V, HEIHAK 06231043, 18 in, 3-pack
$33 – $40
3 models
Biugaaufai 6 Inch locking C-clamp set, ZTUKOMN 4 in drill press vise, Monster & Master MM 10 in V-pad locking clamp
$135 – $185
3 models
Magswitch MagSquare 165, KAKA INDUSTRIAL AC-100, Sawyer Mfg Company Welder’s 3rd Hand pipe clamp
Specifications: manufacturer sheets for welding and metalworking machines and the matching Amazon product pages. Prices and availability: Keepa.
Most recent revision in this category: October 7, 2026.
Prices quoted in these summaries are dated readings. The live price is shown next to each product.