An air grinder uses around 450 l/min at 6.3 bar as a guide. For a grinder used for long minutes without a break, allow at least 560 l/min with the margin: a 7.5 kW 4-in-1 screw compressor such as the K 75, which delivers 1.1 m³/min at 8 bar, runs it with room to spare. For two grinders at once, move up to the K 110.
This article covers one or two grinders. The other uses of air in the workshop are on our page on compressors for metal fabrication.
How much air does your grinder use?
Our configurator uses 450 l/min for an air grinder or cut-off tool, at about 6.3 bar. That is an average: the spread between tools is wide.
- A small straight die grinder for touch-up or deburring uses clearly less.
- A 125 mm angle grinder is often around that value.
- A large-diameter angle grinder uses more, and can approach or exceed 1,000 l/min.
The right figure is in the manufacturer's manual, at the working pressure. Note the tool's power too: at the same disc size, a more powerful grinder needs more air.
The calculation, step by step
Step 1, real use. The configurator counts a grinder as an intermittent tool, at half. That is right for a quick deburr between welds. But when you grind a weld along its full length or prepare parts in batches, the grinder runs without a break: count it at 100 %.
Step 2, one grinder running continuously.
450 l/min × 1.25 margin = about 560 l/min.
Step 3, two grinders running continuously plus a blow gun.
- Grinders: 2 × 450 = 900 l/min.
- Blow gun: 150 l/min as a guide, counted at half, so 75 l/min.
- Subtotal: 975 l/min.
- With the 25 % margin: 975 × 1.25 = about 1,220 l/min.
The K 75 delivers 1,100 l/min at 8 bar: it is no longer enough. The K 110 delivers 1.7 m³/min at 8 bar and keeps a reserve. Beyond three grinders, our article on grinders and chipping hammers on a 22 kW compressor details the sizing of a fettling station.
Piston or screw?
| Use | Recommended model |
|---|---|
| Occasional grinding, a few minutes at a time | E 75, 0.9 m³/min piston compressor, 180 L receiver |
| One grinder used every day, in long sessions | K 75, 4-in-1 screw compressor, 1.1 m³/min at 8 bar |
| Two grinders at the same time | K 110, 4-in-1 screw compressor, 1.7 m³/min at 8 bar |
A piston compressor needs rest time between cycles. A grinder running for twenty minutes straight keeps it working non-stop: that is where a screw compressor is the right choice. Our guide screw or piston compressor covers this decision.
Pressure at the tool, the real problem
A grinder that "lacks power" almost always lacks pressure at the tool inlet, not compressor capacity. The usual causes:
- a hose that is too thin or too long: pressure drops as soon as the grinder runs;
- quick couplings that are too small, which choke the flow;
- a regulator set at rest, not with the trigger pulled.
Measure the pressure at the grinder inlet while it is working. If it falls below the working pressure in the manual, fix the network before raising the compressor setting. Our guide to connecting to the air network helps you choose pipe sizes, and our page on quick couplings explains how to pick the bore for the tool.
Other points to watch
- Tool lubrication. Many grinders need a few drops of oil. Follow the manual: a lubricator at the grinding station or oiling by hand, never on a line feeding a spray gun or a plasma cutter.
- Water. Wet air wears the tool motor. The built-in dryer of the 4-in-1 models takes care of this.
- Sparks and dust. Install the compressor away from the grinding station and check its intake filter.
For a first figure, enter your tools in the configurator, then send us your grinder's data sheet with a quote request.
For your trade: Compressor for metalwork and fabrication shops.