Bar clamp buying guide UK
Updated: 22 October 2026
You have a frame or a small repair in mind, and the amazon.co.uk title offers one number: 6 inch, 150 mm or 300 mm. A bar clamp buying guide UK has to split that number into three checks. Jaw opening, throat depth and stated force are not the same measurement. Measure the stack, including a scrap caul, then the reach in from the edge, then read the kilogram line as a maker claim. The [clamp comparison](/hub/hand-tools/clamp) holds the twelve listings and the GBP prices. Peter F. read those cards on 21 October 2026. We did not measure force. A qualifying purchase through our links can earn us a commission at no extra cost to you.
You have a frame or a small repair in mind, and the amazon.co.uk title offers one number: 6 inch, 150 mm or 300 mm. A bar clamp buying guide UK has to split that number into three checks.
You have a frame or a small repair in mind, and the amazon.co.uk title offers one number: 6 inch, 150 mm or 300 mm. A bar clamp buying guide UK has to split that number into three checks. Jaw opening, throat depth and stated force are not the same measurement. Measure the stack, including a scrap caul, then the reach in from the edge, then read the kilogram line as a maker claim. The clamp comparison holds the twelve listings and the GBP prices. Peter F. read those cards on 21 October 2026. We did not measure force. A qualifying purchase through our links can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Jaw opening | Throat depth | Stated force | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  IRWIN IRWIN Quick-Grip T54122EL7, twin pack | 300 mm | 62 mm | 63 kg | 9.1 | about £14.90 | View offer |
| Best value |  WORKPRO WORKPRO 150 mm ratchet bar clamp, 2-pack | 150 mm | 60 mm | 68 kg | 8.3 | about £12.99 | View offer |
 WORKPRO WORKPRO 305 mm ratchet bar clamp, 2-pack | 305 mm | 60 mm | 68 kg | 8.3 | about £16.99 | View offer |
On this page
Jaw opening is the number in the title
On a one-handed bar, the inch or millimetre in the title is the opening along the bar, not the length of the tool and not the throat. A WORKPRO pair listed at 150 mm opens 150 mm. The IRWIN T54122EL7 is titled at 300 mm, and a bullet also prints a 150 mm to 300 mm range, so you still confirm what is in the box. The DEKO six-piece set states four clamps at 6 inch and two at 12 inch. Those are openings. Measure the stack, including a scrap caul, and leave a margin. Thomas Graham’s job bands, as a guide rather than a law, put general work around 150–300 mm and panels up around 450–900 mm.
Throat depth does not grow with the bar
Throat depth is how far the jaw reaches in from the edge. A longer bar spans a wider frame. It does not press the middle of a wide board. In this set the WORKPRO 150 mm pair and the WORKPRO 305 mm pair both print a 60 mm throat. The IRWIN mini prints 62 mm, which matches the mini row in the maker’s brochure, not a heavy-duty bar. Buy the 305 mm pair when the stack is longer than 150 mm, not because you hope the extra bar will reach the centre of a tabletop. The Amazon Basics set and the DEKO set leave throat blank. The two WORKPRO lengths also share one printed review count of 8,917.
Stated force is a maker claim
The kilogram or pound line is a maker claim, and this project did not measure it. UK Workshop threads treat those packet figures as a maximum. Wonkee Donkee separates force from pressure: the same kilogram on a small hard jaw dents the face, while a wider pad spreads it. Stop when the joint is closed. The IRWIN mini is titled at 63 kg, the brochure’s light-duty row, not the 136 kg or 272 kg rows. The WORKPRO pairs state up to 68 kg, while the 150 mm highlight also prints 68 kg (50 lb). Those conversions do not match, because 68 kg is about 150 lb. Distrust the 50 lb line. ManoMano’s “about 100 kg” for one-handed clamps is a class rule of thumb, not a test of these rows. None of those figures is a British Standard test, and the General Product Safety Regulations 2005 do not turn a printed kilogram into a measured one.
Pick the type before the brand
A one-handed bar ratchets on a steel bar and, on some listings, reverses into a spreader. One hand can stay on the work. The only screw clamps here open 10–57 mm with 28 mm depth, and reviews say the pads come off. A cast G clamp of about 50–150 mm from a trade seller is a different object. Spring clamps, including the G4GADGET six-pack and the EMART clips, hold fabric and tiny pieces. Corner kits register 90 degrees. A review on the Anylot listing says the squares do not press the glue line. If the photograph shows a square or a spring and the job needs a closed joint, change type before you compare stars. Why “F clamp” on these titles means the trigger bar is on bar clamp vs G clamp. Whether to leave the set for a sash or parallel clamp is on clamps for a wood glue-up.
Common questions
What does the inch size on a bar clamp mean?
On these one-handed bars the inch or millimetre in the title is the jaw opening along the bar. A 6 inch DEKO clamp and a 150 mm WORKPRO clamp are both telling you the opening, not the throat. Measure the stack, including any scrap caul, and leave a little spare. A spring-clamp title can use the same word for the length of the clip, which is what a UK review says about the G4GADGET “3 inch” line.
Why does a 305 mm clamp still list a 60 mm throat?
Throat depth is the reach in from the edge. The WORKPRO 305 mm pair and the 150 mm pair both print 60 mm, and the IRWIN mini prints 62 mm. The longer bar spans a longer stack. It does not press further into a wide board. If you needed the middle of a panel, a longer trigger in this set is the wrong fix.
Is 68 kg a lot, and why does one highlight also say 50 lb?
68 kg is the maker’s stated maximum on the WORKPRO pairs, in the same band as the IRWIN mini’s 63 kg. It was not measured here, and it is not a force you should chase until the wood creaks. The 150 mm highlight that prints 68 kg (50 lb) contradicts the bullets, which say 68 kg (150 lb). Trust the 150 lb conversion and ignore the 50 lb line.
Should a first buy be 150 mm or 300 mm?
Buy 150 mm when the stack, cauls included, fits inside that opening. Buy a 300 mm or 305 mm pair when the stack is longer. In this set both WORKPRO lengths share a 60 mm throat, and the IRWIN 300 mm twin does not describe a spreader. Opening decides the length. Throat and the spreader line decide whether that longer clamp is the right one.
When is a spring clamp or a corner square the wrong first tool?
A spring clamp is the wrong first tool when the joint has to be pulled closed and held while glue sets. A corner square is the wrong first tool when you needed that pull rather than a 90 degree register. Start with a one-handed bar for ordinary DIY holding. Add a spring pack for backdrops, and a square only when the corner itself is the problem.
What is missing if I glue wide panels?
Sash clamps and parallel clamps are not in this set. A wide or bowed panel needs a longer clamp than the job, several of them, and a deeper reach than 60 mm. The light-duty bars here can hold a small closed joint. They are not the panel kit. That exit is the point of the glue-up page, not a hidden row in the price table.
Related pages
Sources
Public UK sources from the research digest. Shelf prices and star lines are the amazon.co.uk figures filed on 21 October 2026.
- Thomas Graham, clamp size and clamping force (retrieved 21 October 2026)
- Thomas Graham, G clamps vs F clamps (retrieved 21 October 2026)
- HSE, PUWER overview (retrieved 21 October 2026)
- HSE L114, safe use of woodworking machinery (retrieved 21 October 2026)
- HSE, woodworking standards (retrieved 21 October 2026)
- General Product Safety Regulations 2005 (retrieved 21 October 2026)
- Consumer Rights Act 2015, section 9 (retrieved 21 October 2026)
- IRWIN workholding brochure (retrieved 21 October 2026)
- UK Workshop, clamps and where to start (retrieved 21 October 2026)