A needle scaler is a pneumatic tool in which a bundle of loose steel needles is driven back and forth at high frequency by compressed air, to strip rust, paint, weld slag or concrete laitance from a surface. Because each needle moves independently, the bundle follows the shape of whatever it is working on — including corners, weld seams and structural sections.
How it works
A piston in the cylinder strikes the back of the needle bundle, and the needles pulverise the layer being removed. Common tools carry 19 to 30 needles of 2 to 4 mm diameter and deliver several thousand blows per minute. They run at around 6 bar working pressure with an air consumption of roughly 100 to 300 litres per minute — a small hobby compressor will not keep up, so a machine with a decent output and a receiver is needed.
Applications
- De-rusting steelwork — railings, beams, handrails, machine frames and ship plating
- Removing weld slag and spatter — straight after welding, without damaging the parent metal
- Removing laitance — scabbling concrete before a new topping or repair mortar is applied
- Paint removal — stripping old coatings from steel or stone where blasting is not an option
- Texturing stone — giving natural stone or concrete a punched, roughened finish
Points to watch
- Hearing protection, eye protection and gloves are essential: noise levels are high and sharp fragments fly off
- Old coatings on steel may contain lead, and some older primers hexavalent chromium; have the coating tested and put controls in place before scaling
- The tool produces substantial hand-arm vibration. Rotate operators, choose an anti-vibration model and keep an eye on daily exposure
- Use pointed needles for fine work and chisel-tipped needles for hard, thick layers; replace broken needles at once or the bundle runs out of balance
- On thin sheet the tool can stretch and distort the metal — work there with light pressure and short bursts
Related terms
- Chipping hammer
- Rust
- Abrasive blasting
- Compressed air
- Coating
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