What Grit Flap Disc for Stainless Steel vs General Metal? A Buyer's Guide

Why Grit Selection Matters

Grabbing the wrong grit costs you time and money — too coarse and you risk gouging your workpiece or leaving scratches that take twice as long to remove; too fine and you're burning through discs without removing enough material. Getting grit right the first time is one of the simplest ways to work faster and spend less on consumables.

The Grit Scale at a Glance

Flap disc grits typically run from 36 (very coarse) up to 120 (fine). As grit number goes up, the abrasive grain gets finer and cuts more slowly but leaves a smoother surface.

• 36G – Very aggressive. Heavy stock removal, weld seam grinding, deburring thick material.
• 40G – Aggressive. The go-to workhorse for blending welds and grinding scale on mild steel.
• 60G – Medium. Blending and intermediate finishing after coarser grits.
• 80G – Fine. Light stock removal and pre-finishing.
• 120G – Very fine. Final finishing and surface prep before paint or coating.

Grit Guide for Stainless Steel

Stainless steel is unforgiving. Deep scratches are difficult to remove and cross-contamination from carbon steel particles can cause rust pitting. Follow these rules:

• Weld blending & heavy grinding: Start with 40G. It's aggressive enough to remove material without the deeper scratch pattern of 36G that you'd have to work back out.
• Blending & smoothing: Step up to 60G to knock back the 40G scratches.
• Pre-finish / paint or passivation prep: Finish with 80G or 120G for a consistent surface ready for treatment.
• Key rule: Never use a disc that has touched carbon/mild steel on stainless — keep dedicated discs for SS work.

For stainless steel, ceramic and zirconia grain types outperform aluminium oxide because they self-sharpen under heat and last significantly longer. Our Ceramic Flap Disc 4-1/2" for Stainless Steel & Metal Grinding is purpose-built for exactly this application.

Grit Guide for Mild Steel & General Metal Fabrication

Mild steel is more tolerant and you have more flexibility:

• Heavy stock removal, thick welds, casting flash: 36G — maximum aggression where surface finish is secondary.
• General weld blending & scale removal: 40G — the most common all-purpose starting grit in a fabrication shop.
• Blending after coarse grinding: 60G — smooths out the 36/40G scratch pattern.
• Finishing before paint or powder coat: 80G–120G — achieves a clean, consistent profile for coating adhesion.

Zirconia is the economical workhorse for mild steel. Our Zirconia Flap Disc range includes 36G through 80G options in 4-1/2" and 5" sizes to cover the full progression.

Quick Reference: Grit by Task

Task	Stainless Steel	Mild Steel
Heavy stock removal / thick welds	40G	36G–40G
Weld blending / scale removal	40G–60G	40G–60G
Intermediate finishing	60G–80G	60G–80G
Pre-paint / pre-coating finish	80G–120G	80G–120G

Progression Tips

Never skip more than one grit step. Going straight from 36G to 80G leaves deep scratches that the 80G disc can't efficiently remove — you'll spend more time and burn through more discs than if you'd worked through 60G in between. A two- or three-step progression always wins for surface quality.

Shop Flap Discs by Grit

Browse our full range of flap discs manufactured in Canada — available in zirconia and ceramic grain types, in multiple sizes and grits to suit your application. All ABRACUT discs are built to professional standards and priced for production use.