Abrasives

Three variables decide whether an abrasive suits the job:

• Abrasive grain. Aluminium oxide is the general-purpose choice for steel. Silicon carbide is harder and sharper, suiting stone, glass and non-ferrous metal. Zirconia and ceramic grains self-sharpen under pressure, which is what makes them worth the money on heavy stock removal.
• Grit size. Lower is coarser. Coarse grit removes material; fine grit refines finish. Skipping more than one grit step leaves scratches the next step cannot clear.
• Bond and backing. Resin bonds suit high-speed cutting and grinding; cloth backings flex around contours where paper backings tear.

This is the mistake that causes the most expensive rework. Abrasives used on carbon steel pick up iron particles, and those particles embed in stainless steel and rust — so a stainless fabrication finished with a contaminated abrasive grows rust spots days later, and the finish has to be redone.

Use abrasives certified low in iron, sulphur and chlorine on stainless, and keep them segregated from carbon steel work. Aluminium has a different problem: it is soft and loads abrasives quickly, so it wants open-coat products, often with a lubricant coating to stop clogging.

Grinding wheels and points is the largest group, covering cutting and grinding discs, mounted points and bench wheels. Sanding belts and sanding pads cover linishing and orbital work, and abrasive sheets and abrasive rolls cover hand work.

Polishing pads covers finishing and compounding, and pipe brushes covers internal cleaning and deburring.

A bonded wheel that comes apart at speed is genuinely dangerous, and almost every failure is preventable. Never exceed the maximum RPM marked on the wheel — that marking is the limit, not a suggestion, and a wheel fitted to an overspeed grinder can burst. Match the wheel to the guard and the machine it was made for.

Check for cracks before fitting, and never use a wheel that has been dropped. Cutting discs are made for cutting, not side grinding; loading a thin cutting disc laterally is how they shatter.

Respirable crystalline silica is the other hazard here. Grinding and cutting masonry, concrete and engineered stone generates silica dust, and Australian exposure limits have tightened substantially. Water suppression or on-tool extraction plus appropriate respiratory protection is required, not advisory. See Safe Work Australia’s crystalline silica guidance for current requirements.

Tell us the material, the machine and the finish you are chasing, and we will specify grain, grit and backing. Quote a part number and we will source it, or identify an equivalent where a line has been superseded.

Resin-bonded abrasives absorb moisture, and a wheel that has sat in a damp shed loses strength unevenly. Most bonded wheels carry an expiry date for exactly this reason, and it is worth reading before fitting something that has been on the shelf for years.

Store wheels flat or supported on edge, dry, and away from impact. Coated abrasives curl and crack if stored in heat or hung under their own weight. Belts in particular should be hung on a wide support or stored flat so the joint is not stressed.

Buying abrasives in bulk only saves money if the storage is right. Where turnover is slow, smaller and more frequent orders cost less than replacing a pallet of perished wheels.