Abrasive Grit Guide P24-P120 for metalworking | Universal Abrasives

What Grit Abrasive Should I Use? A Guide to Choosing the Right Grit for Metalworking

Choosing the correct abrasive grit can make a significant difference to grinding speed, surface finish, abrasive life and overall productivity.

Using a grit that is too coarse can remove more material than necessary and leave deep scratches, while using an abrasive that is too fine can dramatically increase the time required to complete a job.

Whether you're removing welds, deburring components, preparing steel for painting or producing a finished stainless steel surface, understanding abrasive grit sizes will help you choose the right product for the application.

Quick guide:

  • P24–P36 – Heavy stock removal
  • P40–P60 – Weld removal and general grinding
  • P80 – Blending and surface preparation
  • P120 – Fine finishing

What Does Abrasive Grit Mean?

Abrasive grit refers to the approximate size of the abrasive particles used on a disc, belt, sheet or other abrasive product.

As a general rule:

Lower grit numbers = coarser and more aggressive abrasives

Higher grit numbers = finer abrasives and smoother finishes

For example, a P24 abrasive is considerably more aggressive than a P120 abrasive.

Coarse abrasives are normally used when rapid material removal is required, while finer abrasives are used for blending, surface preparation and finishing.

Quick Abrasive Grit Guide

P24–P36: Heavy Stock Removal

Coarse grits such as P24 and P36 are designed for aggressive grinding and rapid material removal.

Typical applications include:

  • Heavy weld removal
  • Removing large amounts of material
  • Grinding rough edges
  • Preparing heavily corroded surfaces
  • Removing scale
  • Heavy fabrication work

A P36 fibre disc, for example, can provide extremely fast stock removal when used with the correct backing pad.

These coarse grits are ideal when speed is more important than the final surface finish.

P40–P60: General Grinding and Weld Removal

P40 and P60 are among the most useful grit sizes for general metal fabrication.

They provide a good balance between material removal and surface finish.

Typical applications include:

  • Weld removal
  • Weld blending
  • Deburring
  • Edge preparation
  • Surface grinding
  • Removing imperfections
  • General fabrication work

For many fabrication workshops, P40 or P60 flap discs and fibre discs provide an excellent starting point for everyday grinding applications.

P80: Blending and Surface Preparation

P80 provides a noticeably finer finish while still offering useful material removal.

It is commonly used for:

  • Blending welds
  • Removing grinding marks
  • Preparing surfaces for painting
  • Deburring
  • Surface preparation
  • General finishing work

P80 can also be useful as an intermediate stage between aggressive grinding and final finishing.

For example, a fabricator may remove a weld using P40 before progressing to P80 to refine the surface.

P120: Fine Finishing

P120 abrasives provide a considerably finer finish and are generally used once the majority of material removal has already been completed.

Typical applications include:

  • Fine blending
  • Surface preparation
  • Removing lighter scratches
  • Preparing metal before coating
  • Refining surfaces before further finishing
  • Stainless steel finishing processes

Using P120 for heavy grinding would normally be inefficient because the finer abrasive grain removes material more slowly.

Instead, it should generally be used later in the finishing process.

Should You Start With a Coarse or Fine Grit?

One of the most common mistakes in abrasive selection is starting with an abrasive that is too fine.

If significant material needs to be removed, using a fine grit can substantially increase grinding time.

A more efficient process is normally to start with the finest grit that will still remove the required material at an acceptable rate.

This helps avoid unnecessarily deep scratches while maintaining good productivity.

For example:

Heavy weld removal: Start around P36–P40

General weld blending: P40–P60

Surface preparation: P60–P80

Fine finishing: P80–P120 or finer

The exact grit required will depend on the material, abrasive product, machine and desired finish.

Don't Skip Too Many Grit Sizes

When producing a progressively finer finish, avoid making excessively large jumps between grit sizes.

Deep scratches created by a coarse abrasive can be difficult to remove with a much finer grit.

Instead of moving directly from P36 to P120, for example, a more effective process may be:

P36 → P60 → P80 → P120

Each stage removes the scratch pattern produced by the previous abrasive.

Although this involves additional steps, it can actually reduce total finishing time and produce a much more consistent surface.

Fibre Disc Grit Selection

Fibre discs are particularly effective for aggressive grinding and stock removal.

Coarser fibre discs such as P24, P36 and P40 are commonly used for:

  • Weld removal
  • Edge grinding
  • Heavy deburring
  • Rapid stock removal

Medium grits such as P60 and P80 provide more controlled grinding and improved surface quality.

Finer fibre discs can then be used for surface preparation and finishing applications.

The abrasive grain also matters.

Ceramic fibre discs can provide particularly high cutting performance on demanding materials, while zirconia and aluminium oxide products can provide cost-effective solutions for general fabrication work.

Flap Disc Grit Selection

Flap discs combine grinding and finishing capabilities, making them extremely versatile.

P40 flap discs provide aggressive grinding performance and are commonly used for weld removal and heavy blending.

P60 offers a useful balance between grinding speed and surface finish.

P80 is ideal for lighter blending, deburring and surface preparation.

P120 can be used where a finer finish is required.

Because flap discs expose fresh abrasive grain as the flaps wear, they can provide consistent performance throughout their service life.

Choosing Grit for Stainless Steel

Stainless steel requires careful abrasive selection because excessive grinding pressure and heat can affect surface quality.

For weld removal, a high-performance ceramic abrasive in P36–P60 can provide fast cutting while reducing the amount of pressure required from the operator.

The surface can then be progressively refined using finer abrasives.

Depending on the required finish, additional non-woven or polishing products may then be used.

Always ensure that abrasives used on stainless steel are suitable for INOX applications and avoid contamination from products previously used on carbon steel.

Choosing Grit for Mild Steel

Mild steel is relatively forgiving and can be worked using a wide range of abrasive products.

For heavy weld removal and fabrication work, P24–P40 abrasives provide aggressive material removal.

P40–P60 works well for general grinding and weld blending.

P80–P120 can then be used for surface preparation and finishing.

The best combination will depend on whether productivity, abrasive life or final surface quality is the main priority.

Grit Isn't the Only Factor

Although grit size is important, it is only one part of abrasive selection.

Performance is also influenced by:

  • Abrasive grain type
  • Disc construction
  • Backing material
  • Grinding pressure
  • Machine speed
  • Contact angle
  • Material being worked
  • Required surface finish

Two P60 abrasive products can therefore perform very differently.

A premium ceramic P60 abrasive designed for industrial grinding may offer considerably different cutting performance and service life compared with a conventional aluminium oxide P60 product.

This is why abrasive selection should be based on the complete application rather than grit size alone.

Which Abrasive Grit Should You Choose?

As a simple starting point:

P24–P36 — Heavy grinding and rapid stock removal

P40–P60 — Weld removal, general grinding and deburring

P80 — Blending and surface preparation

P120 — Fine finishing and surface refinement

If you're unsure, selecting the correct abrasive and grit for your particular material and application can significantly reduce grinding time, abrasive consumption and overall process costs.

Need Help Choosing the Right Abrasive?

At Universal Abrasives, we supply professional abrasive solutions for fabrication, engineering, manufacturing and metalworking applications.

Our range includes fibre discs, flap discs, grinding discs, quick-change abrasives, surface conditioning products and specialist PFERD abrasives for demanding industrial applications.

Whether you're working with mild steel, stainless steel, aluminium or specialist materials, we can help identify the right abrasive type and grit for your application.

Contact Universal Abrasives today for product advice or arrange a FREE abrasives appraisal to identify opportunities to improve performance and reduce abrasive costs.

Universal Abrasives Limited

📞 0121 537 5930
✉️ sales@universalabrasives.co.uk

Registered Office: 66 Main Street, Austrey, Atherstone, Warwickshire CV9 3EG
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