For stone carving with a pneumatic hammer, allow around 150 to 400 l/min per hammer in use. A stonemason working alone with one hammer and a blow gun is well served by a 5.5 kW screw compressor such as the S 55, which delivers 0.6 m³/min at 8 bar. A workshop of two or three masons striking at the same time moves up to the K 75, 1.1 m³/min at 8 bar with a built-in air receiver, dryer and filtration.
This article deals with carving hammers and chisels. For every use of air in a stone workshop, engraving and polishing included, see our page on the compressor for stonemasons.
Which pneumatic tools does a stonemason use?
The pneumatic carving hammer holds a steel or carbide tool: chisel, claw chisel, point, bush hammer head. A piston strikes the tool several thousand times a minute. The mason guides it, the hammer supplies the force. They come in several sizes:
- small sculpting and hand-lettering hammers, light, for detail, cut lettering and finishing;
- medium carving hammers, for dressing a face, cutting a moulding, reworking an ashlar face;
- large hammers and bush hammers, for roughing out a block or texturing a granite surface.
The bigger the hammer, the harder it strikes and the more air it uses. The exact figure is in the manual, often in l/min, sometimes in CFM. Our flow and pressure converter switches from one unit to the other.
How much air does a carving hammer use?
Values given as a rough guide, at a pressure of around 6 bar:
| Type of hammer | Indicative consumption |
|---|---|
| Small sculpting or lettering hammer | around 100 to 200 l/min |
| Medium carving hammer | around 200 to 300 l/min |
| Large hammer, bush hammer | around 300 to 400 l/min |
| Blow gun, to clear chips | around 150 l/min while blowing |
The key point is how the tool is used. An impact wrench works in bursts: it tightens, then stops. A carving hammer strikes almost without interruption while the mason works across the stone. Our configurator therefore counts it at 100%. The blow gun, on the other hand, is used now and then: it is counted at half, and the air receiver absorbs its peaks.
What pressure for a pneumatic carving hammer?
Most hammers work at around 6 bar at the tool inlet. For fine detail, many sculptors lower the pressure with a regulator at the station: the hammer strikes more gently and the tool is easier to control. The compressor itself stays set at around 7 to 8 bar to cover the losses in the network and the hose.
There is no point going higher. An over-fed hammer strikes harder but tires the wrist, wears the tool faster and makes the network leak more. If the pressure falls below 5 bar at the tool, the hammer loses its punch: check the bore and length of the hose before changing compressor. The pressure drop calculator shows what your line is losing.
The step-by-step calculation
Case 1, a stonemason working alone.
- Medium carving hammer: 250 l/min, counted at 100%.
- Blow gun: 150 l/min, counted at 50%, giving 75 l/min.
- Subtotal: 325 l/min.
- 25% safety margin: 325 × 1.25 = 406 l/min.
- 20% expansion margin: 406 × 1.2 = about 490 l/min (around 17 CFM).
The S 55 delivers 600 l/min at 8 bar: it covers this need, with a reserve for a small lettering hammer as well.
Case 2, a workshop of three masons.
- Two medium hammers: 2 × 250 = 500 l/min.
- One bush hammer: 350 l/min.
- One blow gun at 50%: 75 l/min.
- Subtotal: 925 l/min.
- With both margins: 925 × 1.25 × 1.2 = about 1,390 l/min.
The K 75 and its 1,100 l/min are no longer enough. The K 110, an 11 kW 4-in-1 unit, delivers 1.7 m³/min at 8 bar and covers the workshop. Without the bush hammer, the total with margins falls to around 860 l/min and the K 75 is enough.
Which compressor for your workshop?
| Workshop | Need with margins | Recommended model |
|---|---|---|
| Sculptor or stonemason working alone, one hammer | 400 to 550 l/min | S 55, 0.6 m³/min at 8 bar, with air receiver and dryer |
| Two medium hammers, or three small ones | 700 to 1,000 l/min | K 75, 1.1 m³/min at 8 bar, 420 L receiver |
| Three stations including a bush hammer or large hammer | 1,200 to 1,600 l/min | K 110, 1.7 m³/min at 8 bar |
| Carving and sandblast engraving in the same workshop | depends on the nozzle | see our article on sandblast engraving |
A piston compressor can be enough for a sculptor who works a few hours a week. But a carving hammer runs for a long time: a piston unit running continuously gets hot and wears quickly. Our article on the difference between piston and screw compressors explains why the screw is more at ease in this case. The S and K series are also variable speed: when the mason puts the hammer down, the compressor slows down instead of running idle.
The pitfalls of stone carving
- Water in the hammers. A hammer that spits water rusts inside and loses its punch. A refrigerated dryer at the compressor outlet solves the problem; it is built into the K series.
- Lubrication. Many hammers need a few drops of air tool oil, at the inlet or through a lubricator at the station. Follow the manual: dry air from the compressor is not a lubricant.
- Dust drawn in by the compressor. Carving gives off a fine dust. Place the compressor outside the workshop, with an air intake on the clean side. See our article on silica dust and the compressor.
- Quick couplings. They vibrate with the hammer and end up leaking. Check them regularly: a leak runs day and night. Our article on how to detect and repair leaks gives the method.
- Work on site. To recarve a monument in situ, screw compressor hire avoids tying up the workshop machine.
For the final choice, enter your hammers in the configurator, then send us their manuals with a quote request.
For your trade: Compressor for stonemasons, memorial masons and worktop fabricators.