Tin Snips and Aviation Snips: Colour Codes, Technique, and What to Buy

Your roofer finishes the roof junction and tells you the flashing needs trimming to fit. You grab a pair of scissors from the kitchen. They mangle the zinc, can't get through the fold, and now the edge is bent and ragged. A £6pair of tin snips from Toolstation would have cut it clean in seconds. These are one of the cheapest tools you'll buy for a build, and one of the most useful whenever sheet metal, mesh, or metal framing needs cutting to size.

What they are and when you need them

Tin snips are heavy-duty hand shears built for cutting thin sheet metal. They look like oversized scissors but with shorter, thicker blades and longer handles to give you mechanical advantage (more cutting force for less hand effort). The blades are hardened steel, often with serrated edges that grip the metal as you cut.

You'll reach for them during an extension whenever you need to cut roof flashing (zinc or aluminium strips that seal joints between the new roof and existing walls), metal cable trunking for first-fix electrics, metal stud track for partition walls, wire mesh, or ventilation ducting. None of these jobs need a power tool. Tin snips handle them quietly, quickly, and with precision.

Two types exist, and the difference matters.

Traditional tin snips (also called "Gilbow" snips in the UK, after the Gilbow brand that became the generic name since 1924) have a single pivot like scissors. Long handles, short blades, simple construction. They cut thicker material than aviation snips and produce a cleaner, smoother edge because the blades are smooth rather than serrated. But they demand more hand strength and tire you out faster on longer jobs. UK welders on trade forums still swear by 40-year-old Gilbow pairs that "cut like a hot knife through butter."

Aviation snips (also called compound-action snips) have a double pivot mechanism that multiplies your grip force. They're spring-loaded so the handles open automatically between cuts, and they lock shut for storage. Lighter to use, more manoeuvrable, and the standard choice for most DIY and trade work on sheet metal up to about 1.2mm thick.

For a homeowner managing a build, aviation snips are the ones to buy. You won't be cutting heavy plate steel. You'll be making occasional cuts on thin flashing, cable trunking, and stud track. Aviation snips handle all of that with less effort.

The colour code: red, yellow, green

Aviation snips come in three colour-coded variants. This isn't branding. It's an industry standard that tells you which direction the snips are designed to cut.

The colour tells you which way the waste metal curls away from the cut. Yellow (straight) is the one you'll use 90% of the time during a build. The red and green variants are for cutting curves and circles in ductwork or fabrication.

A memory trick borrowed from nautical navigation: red means port (left), green means starboard (right). Same as boat navigation lights. If that sticks, you'll never pick up the wrong pair.

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If you try to cut a left-turning curve with green (right-cut) snips, the metal fights you. It buckles, jams, and the cut wanders. This is the single most common beginner mistake with aviation snips, and it ruins material fast. One DIYUK user tried to cut around a corner with the wrong type and "couldn't get round the corner without" mangling the workpiece.

How to use them properly

The technique is simple but there are specific habits that prevent ruined cuts and wrecked tools.

Marking and positioning

Mark your cut line on the metal with a fine marker or scriber. Position the snips so the metal sits as deep into the jaws as possible, close to the pivot point. Cutting at the tips of the blades wastes your mechanical advantage and produces a ragged edge.

The cutting action

Open the handles fully. Close them about two-thirds of the way. Not all the way shut. Closing the blades completely to the tips creates a small dimple or notch at the end of each bite, leaving a stepped edge instead of a smooth one. Two-thirds closure, lift, reposition, repeat. Keep the blades in constant contact with the metal between bites.

With traditional Gilbow-style snips, keep the tool upright. The flat part of the inner blade must sit parallel to the sheet metal surface. Twisting the snips sideways stretches the connecting bolt and eventually ruins the joint. Aviation snips are more forgiving because the compound mechanism absorbs more lateral force.

The three-cut technique for clean edges

Don't cut directly on your marked line. Make the initial cut 3-5mm away from the line on the waste side. Then trim closer, halving the remaining waste. Then make the final cut right on the line. The blade on the "keep" side must lay flat against the material throughout.

Done correctly, the scrap curls into a tight spiral and the kept edge stays flat and clean. On thin material (under 0.8mm) one preliminary cut is enough. On thicker sheet, the full three cuts give noticeably better results. This is a professional fabrication technique that most DIY guides skip entirely, and it's the difference between a rough edge and one that looks like it came from a guillotine.

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Managing the waste strip

As you cut, the waste side curls upward (or to the side, depending on your snip type). Don't fight it. Let it curl. Bending the waste strip back and forth weakens the metal and makes your cut harder. Once you've finished, snip the waste strip free or bend it off.

Cutting internal holes

To cut a hole in the middle of a sheet (for a vent opening or pipe penetration), you can't start from an edge. Punch or drill a pilot hole inside the marked circle. A screwdriver driven in at 45 degrees with a hammer works if you don't have a drill to hand. Insert one blade of the snips through the hole, then spiral outward toward the cut line. Don't cut directly on the line from the pilot hole. Expand outward in a gradual spiral, then make the final cut on the marked line. This prevents distortion around the opening.

After cutting

Every cut edge is sharp enough to need stitches (see the safety section below). File or deburr the edges with a flat metal file before handling the piece further. This takes 30 seconds and saves skin.

What they'll cut (and what they won't)

Aviation snips rated for 18 gauge will handle:

• Mild steel up to about 1.2mm thick (18 gauge). This covers standard flashing, cable trunking, metal stud track, and thin steel sheet.
• Galvanised steel at 18-20 gauge. Roofing accessories, mesh, ducting.
• Aluminium, copper, and brass comfortably up to 1.0mm, and some models up to 1.5mm in aluminium. Zinc and aluminium flashing alternatives to lead fall squarely in this range.
• Plastic sheet, leather, and carpet on some models (check the manufacturer's spec).

They won't cut hardened steel, thick plate, screws, nails, or wire rope. Forcing these through the blades chips or rolls the cutting edge. For anything thicker than 1.2mm steel, an angle grinder with a cutting disc or a hacksaw is the right tool.

Serrated vs smooth blades

Most aviation snips have serrated jaws. The serrations grip the metal and prevent slippage during cutting, which is exactly what you want on galvanised steel, mild steel, and general sheet work. But serrated edges leave tiny marks on the cut surface, and on soft metals like zinc, copper, and aluminium, those marks create micro stress-risers that can cause the metal to tear or crack over time.

If you're cutting zinc or aluminium flashings that will be exposed to the weather for decades, smooth-jawed snips (like the traditional Gilbow) give a cleaner edge without stress risers. Some professionals who work mainly with natural metals disassemble their aviation snips and grind off the serrations. For a homeowner making a few flashing cuts, serrated is fine. But if you're installing zinc flashings on a roof junction and want longevity, it's worth knowing the distinction.

What to buy

Tin snips are cheap. Even the good ones. Here's what's available at UK retailers in 2026.

Budget: £5 – £12

Single pairs from own-brand ranges. The Minotaur straight aviation snips at Toolstation (£5.99), the Magnusson straight at Screwfix (£6.99), and the OX Trade straight (£7.79from Wickes) all do the basic job. For a homeowner making ten cuts across an entire build, these are fine.

A three-piece set (straight, left, right) at this tier costs £12 – £15. The Minotaur 3-piece at Toolstation (£14.48) gives you all three colours for less than a single mid-range pair. If you're unsure which direction you'll need to cut, a budget set covers all bases.

The trade-off: budget snips have softer blades that dull faster and handles that tire your hands on extended use. For occasional cuts during a build, that doesn't matter.

Mid-range: £14 – £24

This is where the Stanley FatMax and Irwin Gilbow sit, and where UK tradespeople start paying attention.

The Stanley FatMax straight aviation snips (yellow handles, compound action) run £14.99at Screwfix or £16.98at Toolstation. Drop-forged alloy blades with serrated edges, rated for 18 gauge mild steel (up to 1.2mm). Bi-material handles with a one-handed latch release. This is the bestseller for good reason: it works, it lasts, and it doesn't cost much. Professional review testing rated it as one of the most versatile straight-cut snips available.

The Irwin Gilbow general purpose snips at Toolstation (£12.48) are traditional single-pivot tin snips, not aviation style. Drop-forged carbon tool steel, double hollow ground blades (which reduce cutting friction), and safety stops to prevent trapped fingers. These give a cleaner, smoother cut edge than aviation snips but require more hand strength. UK welders and roofers on trade forums consistently rate vintage Gilbow as the gold standard for traditional snips, and the modern ones are still respectable.

The DeWalt Ergo straight aviation snips at Screwfix (£19.99) have cold-forged chromium-vanadium blades and a comfortable bi-material grip. A solid choice if you already use DeWalt tools and want handles that don't punish your hand on longer jobs.

Premium: £22 – £30

The Bahco MA421 compound straight-cut (around £22from specialist retailers) use chromium-molybdenum steel and cut up to 1.5mm mild steel. Bahco (owned by Snap-on) is well-regarded for hand tools, and the MA series are built to a higher spec than most at this price.

Milwaukee straight-cut aviation snips (£17.99from ITS) use chrome-plated chromium steel hardened to 65 HRC, with ergonomic overmoulded grips. Opinions on Milwaukee snips are genuinely split across forums, with some tradespeople praising the handles and others finding the cutting action stiff. At this price, they're worth trying if you already use Milwaukee tools.

The Wiss M-3R Metalmaster (around £22.99) is a larger straight-cut aviation snip. Wiss has been the go-to brand on UK building sites for decades. But professionals note that quality has slipped since they switched from forged to cast steel blades. Midwest snips (forged, not cast) are now preferred by professionals doing volume work, but they're harder to find in UK retailers.

Checking your snips are working properly

Tin snips don't need calibration, but they do wear.

Blade test. Close the blades slowly and watch the cutting edges meet. They should come together evenly along the full length, with no gap and no overlap. If the blades cross or leave a gap at the tips, the pivot bolt has loosened or the blades are worn. Tighten the bolt (nut and bolt on traditional snips, rivet on aviation) and recheck. If the gap persists, the blades are done.

Cut test. Cut a strip of thin aluminium or copper sheet. The cut edge should be reasonably clean with no tearing, no stepped ridges, and no sections where the metal folded instead of cutting. Serrated edges from aviation snips are normal. Torn or folded sections mean dull blades.

Spring test (aviation only). Open and release the handles. They should spring open fully and consistently. A weak or broken torsion spring means the handles won't reopen between cuts, and your hand has to do the work. Replacement springs are available for quality brands but rarely worth fitting on budget pairs.

Alternatives

If you only need to make one or two small cuts on thin metal, a hacksaw handles it without buying another tool. Slower, but effective on material up to any thickness.

For heavier gauge metal (above 1.5mm) or long straight cuts on sheet steel, an angle grinder with a thin cutting disc is faster and more powerful. But it throws sparks, makes noise, and requires PPE. Snips are the quiet, safe option for anything within their gauge range.

Hand nibblers are a specialist alternative that professionals mention frequently. A nibbler punches small crescent-shaped bites out of sheet metal without distorting the surrounding material. They produce cleaner results than snips on thin stock (under 1mm) and handle straight lines and curves equally well. The downside: they're slower, they produce tiny sharp offcuts everywhere, and they cause hand fatigue on longer cuts. A Senator or Monodex hand nibbler costs £15 – £30. A good option if you need distortion-free cuts on thin aluminium or zinc.

Where you'll need this

• Roof structure - cutting zinc or aluminium flashing strips and metal straps to size at roof junctions
• First fix electrics - cutting metal cable trunking and metal back boxes to length

These jobs appear across any extension, loft conversion, or renovation project. Anywhere a roofer, electrician, or dry-liner works with thin metal, snips are part of the toolkit.

Safety

Cut sheet metal is genuinely dangerous. Not "be careful" dangerous. "You'll need stitches" dangerous.

Safety glasses protect against small metal fragments that can flick up during cutting, particularly when cutting spring steel or galvanised sheet that has tension in it. Standard practice, low cost, no reason to skip it.