Diamond Blade: How to Choose for Concrete, Tile and Granite

Diamond blade types: segmented, turbo or continuous rim

A diamond blade is a steel core with a diamond-bearing layer on its edge: small synthetic diamond crystals held in a metal bond. The blade does not cut, it grinds the material away. The bond wears gradually and exposes new diamonds until the layer is used up. So the key facts about a blade are which material its bond is designed for and how high the diamond layer is.

By rim shape there are three types, each for its own job:

• Segmented (1A1RSS in the marking) - the layer is split into segments by gullets. The gullets carry away slurry and heat, so the blade cuts concrete, brick and asphalt dry and on large machines. The cut is rougher, with possible chipping at the edge.
• Turbo - a continuous corrugated rim or turbo segments. Cuts faster than a continuous rim and cleaner than a segmented blade. The main choice for concrete, brick and granite with a grinder and no water.
• Continuous rim (1A1R) - a rim without gullets. Gives the cleanest chip-free cut on tile, porcelain stoneware and marble. Classically used with water on a tile saw, but the thin Decor Slim, Razor and Multigres blades are designed by the manufacturer for dry cutting with a grinder.

Which diamond blade for which material: selection table

The bond rule is simple: the harder the material, the softer the bond must be so the diamonds keep renewing. The more abrasive the material (asphalt, green concrete, sandstone), the harder the bond, otherwise its sand eats the layer. That is why a universal blade is always a compromise, and a material-specific blade lasts longer and cuts faster.

Below is a selection by job with the DISTAR blades we sell. Prices are rounded, incl. VAT, at the time of publication. The full range is in DISTAR diamond tools.

Diamond blade for concrete: angle grinder or cut-off saw

For an angle grinder on concrete there are two working options. The turbo Extra Max 232 mm (about 1 800 UAH incl. VAT) is recommended by the manufacturer for concrete, reinforced concrete, brick, sandstone and paving slabs, cutting without coolant. The diamond layer is 12 mm high, which means a reserve for long work.

If the concrete has a lot of rebar or is dense monolithic concrete, take a segmented blade with turbo segments, for example Meteor 230 mm - about 3 300 UAH incl. VAT. It costs more than a turbo blade but is designed for reinforced and hydraulic-structure concrete. Such blades cut rebar inside the concrete, but they should not be used to cut separate steel bars.

Petrol cut-off saws and floor saws need 300-600 mm blades with a 25.4 mm bore. Machine power matters here: the manufacturer rates the Technic Advanced series for saws up to 7 kW, Classic H12 for 4-9 kW equipment, Meteor up to 12 kW. For concrete without heavy reinforcement a balanced option is Classic H12 354 mm, about 5 900 UAH incl. VAT; according to the manufacturer, the series lasts up to 400 m of cut on a cut-off saw.

Asphalt and green concrete are a separate case: they are very abrasive, and an ordinary concrete blade wears quickly on them. For them there are blades with a hard bond and protective segments - Sprinter Plus, Green Concrete, and STAYER for a 230 mm grinder. The full range is in blades for cut-off saws and floor saws.

Diamond blade for tile and porcelain stoneware

Tile needs a continuous-rim blade: segments and turbo rims chip the glaze. With a grinder it is convenient to cut with a thin blade, for example Decor Slim 125 mm with a 1.2 mm diamond layer - about 1 100 UAH incl. VAT. The thinner the layer, the less force and the cleaner the edge, but a thin blade does not tolerate twisting or side pressure.

For very hard porcelain stoneware Razor and Hard ceramics fit, for tile with a decorative glazed surface - Esthete with an ultra-thin layer. For 45° tile mitres there is a separate Edge series, 180-250 mm with a 25.4 mm bore - it is for a tile saw, not for a grinder.

Wet tile saws use continuous-rim 1A1R blades with a 25.4 or 32 mm bore. For example, Granite 200 mm (about 1 450 UAH incl. VAT) is intended by the manufacturer for granite and dense sandstone; according to its data, it lasts up to 700 running metres at up to 1.2 m/min. For marble, dolomite and travertine there is the Marble series.

Whether to cut dry or wet is defined by the description of the specific blade, not by the rim type. If the passport says "with cooling", the rim overheats without water and the core may warp. If the blade allows dry cutting, cut in short passes and let it cool at idle. All blades for grinders and tile saws are in diamond blades for angle grinders and tile saws.

Diameter, bore and marking: how to read a blade name

Choose the diameter for the tool, not for the cutting depth you want. The blade must not be larger than the machine guard allows. The exact cutting depth depends on the flange and guard of the specific model.

The main diameter and bore combinations:

• 115-125 mm, 22.23 mm bore - small grinder: chases, tile, shallow cuts.
• 150-232 mm, 22.23 mm bore - large grinder: blocks, kerbs, granite.
• 180-400 mm, 25.4 or 32 mm bore - tile saws and stone-cutting machines.
• 300-600 mm, 25.4 mm bore - petrol cut-off saws and floor saws.

Diamond blade for metal: can you cut steel

Standard diamond blades for concrete, stone and tile are not intended for steel. When cutting iron at high temperature the diamond wears chemically, the rim dulls fast and the blade heats up. Cutting rebar inside concrete with a reinforced-concrete blade is fine; cutting pipe, angle or sheet is not.

Some manufacturers make vacuum-brazed diamond blades for metal - a different design that this article does not cover. For metal use an abrasive cut-off wheel or a saw, and for regular work a metal cut-off machine.

Typical mistakes in choosing and using a blade

Most broken and "burnt" blades are not defects but the result of one of these mistakes. If you need a hole rather than a cut, a blade will not help: see how to choose a diamond core bit and the separate guide on the core bit for socket boxes.

• The maximum speed on the blade is lower than the grinder's no-load speed. This is not allowed: check both numbers.
• A 230 mm blade on a 125 mm grinder or working without the guard. A blade bursting at such speed causes injury.
• A concrete blade on asphalt or sandstone: the abrasive quickly eats the layer and undercuts the core below the segments.
• A continuous "wet" blade used dry without breaks: the rim overheats, the core turns blue and loses flatness.
• Side pressure, cutting curves, grinding with the face of a cutting blade. For grinding there is the diamond cup wheel, which removes material with its face, not its edge.
• The blade glazed over and stopped cutting on hard granite. Make a few cuts in an abrasive material - sand-lime brick or sandstone - to expose the diamonds.