Technologist's guide · Tool selection
How to choose a cut-off saw bladeDiameter, bore, material – dry or wet.
A blade for a hand-held cut-off saw is chosen in three steps. The machine sets the maximum diameter (300, 350 or 400 mm), the bore (usually 20 mm or 25.4 mm) and the speed – cut-off saws run at a fixed spindle speed, about 80–100 m/s at the blade rim, so the blade's permitted speed must be no lower than the machine's (usually 100 m/s). The material sets the bond: concrete and reinforced concrete, abrasive materials (brick, blocks, pavers), asphalt, granite or porcelain each need different blades. The cutting mode sets the construction: dry only with a blade designed for it and in short cuts, and for longer work in concrete – wet, because water binds silica dust.
The key points in 30 seconds
- Diameter and bore – from the machine manual: 300, 350 or 400 mm; bore usually 20 mm or 25.4 mm.
- Speed: the cut-off saw runs at a fixed speed (about 80–100 m/s). The permitted speed marked on the blade core must not be lower – usually 100 m/s.
- Material: concrete and reinforced concrete, abrasive materials, asphalt, granite and porcelain each need a different bond – a “universal” blade is a compromise.
- Dry – only with a dry-cutting blade, in short cuts; wet – for longer work in concrete, because of silica dust.
- Cutting depth: about 100 mm (Ø 300), 125 mm (Ø 350), about 140 mm (Ø 400).
Step 1: which blade will your cut-off saw take?
A hand-held cut-off saw – petrol, electric or battery – sets three parameters you cannot change by choosing a blade. They are on the rating plate and in the manual.
| Blade diameter | Bore | Spindle speed (example) | Peripheral speed | Cutting depth |
|---|---|---|---|---|
| Ø 300 mm (12") | 20 mm / 25.4 mm | approx. 5350 rpm | approx. 84 m/s | approx. 100 mm |
| Ø 350 mm (14") | 20 mm / 25.4 mm | approx. 5350 rpm | approx. 98 m/s | approx. 125 mm |
| Ø 400 mm (16") | 20 mm / 25.4 mm | approx. 4600 rpm | approx. 96 m/s | approx. 140 mm |
Speeds and depths based on popular petrol cut-off saws (manufacturer data for the STIHL TS 410, 420 and 800 series). Depth depends on the flange diameter – larger washers reduce it. Your machine's manual always applies.
- Diameter. Never larger than the machine and its guard allow. Smaller – only if the manual permits it.
- Bore. Many cut-off saws have a 20 mm spindle and blades often have a 25.4 mm (1") bore – a reducing ring joins them. The blade must sit on the spindle without play.
- Direction of rotation. The arrow on the blade core must match the spindle's direction of rotation.
Speed and blade markings – what to check before fitting?
A hand-held cut-off saw has no speed control – it runs at a constant, high speed. That is why 300–400 mm cut-off saw blades are designed for about 100 m/s, much more than wall saw and floor saw blades (typically about 40–55 m/s). On the core of a blade compliant with EN 13236 you will find, among other things:
- Maximum rotational speed (rpm) and maximum peripheral speed (m/s) – neither may be lower than the machine's speed.
- Dimensions: diameter × bore (e.g. 350 × 25.4 mm).
- Direction of rotation and the dry or wet cutting marking.
- The material the blade is designed for (text or pictograms).
A wall saw or floor saw blade of the same diameter is not suitable for a hand-held cut-off saw – it is designed for a lower speed. At too high a speed the core and the segment joints may fail.
Step 2: which blade for which material?
A cut-off saw cuts everything on site – and this is where people most often end up with one “universal” blade. Yet the bond selection rule works just as with large blades: hard material – soft bond, abrasive – hard.
| Material | Blade | What to watch for |
|---|---|---|
| Concrete and reinforced concrete | segmented for concrete; with rebar, impact-resistant grit | feed pressure on bars, hard aggregate (glazing) |
| Brick, hollow blocks, blocks, paving stones | for abrasive materials – hard bond | fast wear of a soft “concrete” blade |
| Asphalt | for asphalt – hard bond, core protection | core undercutting; best wet |
| Granite, granite kerbs, stone | for stone – soft bond | glazing of a universal blade |
| Porcelain, tiles, ceramics | continuous rim or turbo, fine grit | edge chipping with a segmented blade |
| Several materials, occasional cuts | universal | a compromise – shorter life and slower cutting in every material |
If you cut one material most of the time, a blade matched to it usually works out cheaper per metre cut than a universal one – even at a higher purchase price.
Step 3: dry or wet cutting?
A cut-off saw can cut dry – but not with every blade and not without limits.
Dry
- Only with a dry-cutting bladeUsually with laser-welded segments – the joint withstands temperatures at which a braze already softens.
- Short cuts with breaksEvery few dozen seconds take the blade out of the cut and let it cool at idle.
- Dust extraction and respiratory protectionConcrete, stone and ceramics produce silica dust.
Wet
- Water binds the dustThe most effective way to limit dust when cutting concrete and stone.
- Cools the segments and coreLonger blade life and stable running in longer cuts.
- Water kit on the guardTurn the water on before starting – the blade enters the material already wet.
Silica dust is a legal requirement, not just a matter of comfort. Work involving exposure to respirable crystalline silica dust generated by a work process is listed in the EU as carcinogenic work (Directive 2017/2398), with a binding limit of 0.1 mg/m³ for the respirable fraction; some countries set lower national limits. When cutting concrete and stone dry this value is easily exceeded – so for longer work choose wet cutting, or extraction and respiratory protection in line with your risk assessment.
Cut-off saw blade selector – online
Set your machine, material and cutting mode. We will show the blade type, cutting depth and what to check before fitting.
How deep does a hand-held cut-off saw cut?
Cutting depth is roughly (blade diameter − flange diameter) / 2, minus a margin for the guard. In practice: about 100 mm with a Ø 300 blade, 125 mm with Ø 350 and about 140 mm with Ø 400. A thicker element is cut from both sides – with the line marked accurately so the cuts meet.
If you regularly cut elements thicker than about 25–30 cm, walls and slabs, a cut-off saw is no longer the right tool. A wall saw or floor saw or diamond wire works better – faster, without dust and without freehand cutting at full depth.
How can you tell a blade does not suit the job?
- The blade slows down, the segments shine – the bond is too hard for the material (glazing). Typical on granite and concrete with hard aggregate. Short-term fix: a few cuts in brick or block.
- The segments disappear before your eyes – the bond is too soft for an abrasive material: brick, blocks, asphalt.
- A broken segment – impact on bars, overheating when dry or an undercut core. Take the blade out of service immediately – see the diagnosis by symptom.
- The blade “wobbles”, the cut wanders – an overheated core (dry cutting without breaks) or side pressure. A cut-off saw must never cut with the side of the blade or be used to straighten a cut.
- A blue tint on the core – overheating; the core may have lost its tension. Such a blade must be checked before it goes back to work.
More symptoms and their causes: problems and wear diagnosis.
Cut-off saw blade – questions and answers
Which petrol cut-off saw blade for concrete?
A segmented diamond blade for concrete in the diameter and bore approved for the machine (usually 300–400 mm, 20 or 25.4 mm bore), with a permitted speed not lower than the saw's – usually 100 m/s. For reinforced concrete, with impact-resistant grit; for dry cutting, with segments designed for dry cutting.
20 or 25.4 mm bore?
It depends on the saw's spindle. Many cut-off saws have a 20 mm spindle while blades often have a 25.4 mm (1") bore – then you use the reducing ring recommended by the manufacturer. The blade must sit on the spindle without play.
Can I fit a 400 mm blade on a 350 mm cut-off saw?
No. The blade diameter must not exceed the value approved for the machine and its guard. A larger blade also has a higher peripheral speed at the same rpm.
How deep does a 350 mm blade cut on a cut-off saw?
About 125 mm with a typical flange. A Ø 300 mm blade cuts about 100 mm, and Ø 400 mm about 140 mm. Thicker elements are cut from both sides.
Can a cut-off saw cut concrete dry?
Briefly and only with a blade designed for dry cutting, with cooling breaks, dust extraction or respiratory protection. For longer work in concrete and stone, wet cutting is recommended – water binds silica dust.
Does a wall saw blade fit a hand-held cut-off saw?
No, not even with the same diameter. Wall saw and floor saw blades are designed for a lower peripheral speed than a hand-held cut-off saw runs at.
On this topic: diamond tool selection
This guide is part of the hub Diamond tool selection. Related articles:
- Bond, concentration, grit size – how to read a segment specification.
- Concrete blade for granite aggregate – why a “standard” one glazes.
- Asphalt blade vs concrete blade – what happens if you swap them.
- Cutting reinforced concrete: how to avoid losing segments on rebar – feed pressure, cooling, grit.
- Cut-off saw blade finder – series by material and diameter.
- Straight, turbo or roof-top segment – segment shape and starting the cut, cooling and debris.