What do the numbers on a jigsaw blade mean, and which one do I need?

Jigsaw blade codes look arbitrary and are not — they are a de facto standard used across brands, which means a blade code from one manufacturer maps to the same job in another. Learning four or five codes covers everything most people ever cut, and it stops the recurring experience of a blade that will not cut what you bought it for.

Step by step

1. Read the shank letter first.T means a T-shank, the tool-free bayonet fitting used by almost every jigsaw made in the last twenty years. U means a U-shank, an older universal fitting held by a screw. If your saw takes T-shank, only buy T.
2. Read the first digit as length.1 is a short blade, suiting material up to roughly 30mm. 2 is medium, 3 is long for thicker stock, and 5 is extra long. Longer blades flex more and are harder to keep square, so use the shortest blade that will clear the material.
3. Read the next digits as the tooth pattern family.01 and 44 are ground wood teeth. 18 and 27 are milled bi-metal or HSS teeth for metal. 19 is fine metal. 41 and 45 are for plastics and laminates. 08 and 30 sets are commonly special purpose — ceramics, plasterboard, cork.
4. Read the suffix as finish and aggression.A is the finest and cleanest, slow. B is a clean, faster general finish — the everyday wood blade. C is coarser and faster. D is coarsest and fastest, for rough work where the edge does not matter. F on the end means bi-metal construction, which is far more break-resistant.
5. Learn the four codes that cover most work.T101B for general clean cuts in timber and sheet up to about 30mm. T144D for fast rough cuts in timber. T101BR, the reverse-tooth or down-cut blade, for cutting laminate and worktop good-face-up. T118A for thin sheet metal, and T118B for slightly thicker.
6. Note the special-purpose blades worth owning.A T101AO or similar narrow blade for tight curves — the narrower the back of the blade, the tighter it turns. A progressive-tooth blade for material of varying thickness. A carbide-grit blade with no teeth at all for tile, fibre cement and glass fibre.
7. Match tooth count to thickness, not to material alone.The three-teeth-in-the-cut rule applies here too. A coarse D blade in 6mm ply catches and shatters the surface because only one tooth is engaged; a fine A blade in 40mm timber packs its gullets and burns.
8. Check the blade is not bent before blaming the saw.Jigsaw blades bend easily and a bent blade always cuts at an angle. Sight along a blade before fitting it and discard anything that is not straight.

Tips

• Down-cut blades (suffix R for reverse) cut on the downstroke, so the top face stays clean. They also push the saw up off the work, so hold it firmly and clamp the workpiece.
• Bi-metal blades cost a little more and are far less likely to snap, which matters most on long or deep cuts.
• Blades are consumables and cheap in a mixed pack. Working through a job with the wrong blade to save changing it is the most common reason people conclude a jigsaw is inaccurate.
• Some brands use their own numbering. The T-code is stamped on the blade itself even when the packaging uses a house code — read the blade, not the box.

Common mistakes

• Buying by picture on the pack rather than by code — The pictures are generic. The code tells you the length group, tooth pattern and finish precisely.
• Using a wood blade on nail-embedded timber — Ground wood teeth shatter on contact with metal. Reclaimed timber needs a bi-metal nail-tolerant blade.
• Using a long blade in thin material — The extra unsupported length flexes, so the cut bevels through the thickness even though the shoe is flat.

Questions people ask