Flap Disc Grit Differences: Which Grit Is Right for Your Work?

What Is a Flap Disc and Why Are There Different Grits?

A flap disc is made by overlapping sheets of abrasive flaps layered around a wheel. The grit number indicates how coarse or fine the abrasive particles are:

• Lower grit = Coarse → Removes material faster
• Higher grit = Fine → Creates a smooth surface with minimal material removal

Common flap disc grits include #36 / #40 / #60 / #80 / #100 / #120.

Quick Reference Table: Flap Disc Grits Explained

Detailed Grit Guide: How to Choose the Right One

1) Grit #36 – #40 (Very Coarse)

Best for tasks that require fast removal rate or heavy grinding, such as:

• Large weld bead removal
• Deburring thick edges
• Eliminating deep imperfections

Pros: Fast material removal
Cons: Leaves visible grinding marks
Ideal for: Thick steel, structural metal work

Choose this grit if you need speed and aggressive cutting power.

2) Grit #60 (Medium–Coarse)

One of the most commonly used grits in workshops.

• Good grinding speed without being too aggressive
• Smooths out the scratches left by #40
• Suitable for various steel applications

Ideal for users wanting balanced speed and smoother finish.

3) Grit #80 (Standard for Stainless Steel)

Start of the “fine finish” range.

• Minimizes deep scratches
• Works well on stainless steel
• Suitable for thin metal and intermediate smoothing

Perfect when you want a cleaner surface while maintaining efficiency.

4) Grit #100 – #120 (Fine)

Best for fine finishing and pre-polishing, including

• Stainless steel mirror-finishing preparation
• Aluminum finishing
• Wood sanding before coating
  

If your goal is smooth, refined surfaces, choose #100 or higher.

Choosing the Right Flap Disc Type for Your Work

Beyond grit numbers, flap discs also differ by abrasive material and backing type.

1. Aluminum Oxide Flaps (for Steel)

• Best for mild steel
• Budget-friendly
• Pairs well with #40–80

2. Silicon Carbide / Zirconia Flaps (for Stainless Steel)

• Prevents burning on stainless
• Longer lifespan
• Great for #60–120 finishing

3. Hard Backing vs. Flexible Backing

• Hard backing: More aggressive grinding, ideal for thick steel
• Soft backing: Conforms to curved surfaces, ideal for stainless finishing
  

How to Select the Right Flap Disc

1. Consider the Material

• Thick steel → #36–60
• Stainless steel → #80–120
• Wood → #100–120
  

2. Consider Speed vs. Finish

• Faster cutting → Lower grit
• Smoother surface → Higher grit

3. Consider Your Budget

• Heavy-duty use → Premium discs
• Occasional use → Standard discs are sufficient

So Which Grit Should You Choose? (Quick Answer)

• Fast metal removal → #36–#40
• Balanced performance → #60
• Stainless steel finishing → #80
• Fine finishing or pre-polishing → #100–#120

Choosing the right flap disc—correct grit, correct material, and correct backing—will help you achieve cleaner results while saving time and reducing grinding costs.

And if you’re searching for high-quality flap discs with multiple grit options, BTX flap discs from Kings Brite are an excellent choice!