Choosing the right fibre disc grit can make a major difference to grinding speed, disc consumption and surface finish. A grit that is too coarse can leave deep scratch marks, while a grit that is too fine may remove material too slowly.
The best fibre disc grit depends on the amount of material being removed, the type of metal and the finish required. For fabricators and metalworkers, selecting the grit based on the job rather than using the same disc for every application can improve both productivity and results.
What Does Fibre Disc Grit Mean?
The grit number indicates the size of the abrasive particles on the disc. In general, lower grit numbers are more aggressive, while higher grit numbers produce a finer surface finish.
For example, a 36-grit fibre disc is designed for heavier stock removal, while an 80-grit disc is better suited to lighter grinding and surface refinement.
When choosing fibre discs for metal grinding, the grit should match the stage of the fabrication process.
Common Fibre Disc Grits and Their Uses
| Fibre Disc Grit | Best Application |
| 24 Grit | Heavy stock and weld removal |
| 36 Grit | Aggressive grinding |
| 40 Grit | Heavy material removal |
| 60 Grit | General grinding and blending |
| 80 Grit | Surface refinement |
| 120 Grit | Fine finishing |
24 and 36 Grit: Heavy Material Removal
Coarse fibre discs are suitable when the priority is removing material quickly.
They can be used for:
- Heavy weld removal
- Grinding thick steel
- Removing excess material
- Preparing rough metal surfaces
However, coarse grits can leave deeper scratch patterns. If a smoother finish is required, move to a finer grit after the initial grinding stage.
40 Grit: Strong Cutting with More Control
A 40-grit fibre disc provides aggressive cutting while offering more surface control than very coarse grits.
It is commonly used for:
- Weld grinding
- Edge preparation
- Removing moderate stock
- General steel fabrication
For many workshops, 40 grit is a useful choice when the job requires substantial material removal without the extremely rough finish associated with lower grit numbers.
60 Grit: The Versatile Choice
For general fabrication, 60 grit is often a practical all-round option.
It can be used for:
- General metal grinding
- Weld blending
- Surface preparation
- Removing moderate material
- Preparing metal for the next finishing stage
If your workshop handles different grinding jobs, keeping 60-grit X-Flex fibre discs available can provide flexibility for everyday applications.
80 Grit: Smoother Surface Refinement
An 80-grit fibre disc removes less material per pass but creates a finer scratch pattern.
It is suitable for:
- Light weld blending
- Surface refinement
- Removing marks from coarser grinding
- Preparing surfaces before finishing
Use 80 grit when surface appearance matters more than aggressive material removal.
120 Grit: Fine Finishing Applications
A 120-grit fibre disc is designed for lighter material removal and finer surface preparation.
It can be useful for applications requiring:
- Fine surface refinement
- Light finishing
- Reduced scratch depth
- Preparation before coating or additional finishing
Starting with 120 grit on a heavy weld can be inefficient. Fine grits generally work best after the required stock removal has already been completed.
Choose the Grit Based on the Job
Instead of asking which grit is best overall, consider these four questions:
How Much Material Needs to Be Removed?
For heavy stock removal, start with 24, 36 or 40 grit. For lighter grinding, 60 grit or finer may be more appropriate.
What Finish Do You Need?
If the final surface needs further polishing or visible refinement, progressively move from a coarser grit to a finer grit.
What Metal Are You Grinding?
Different metals can respond differently to abrasives. Mild steel, stainless steel and other alloys may require specific abrasive materials and grinding approaches.
How Demanding Is the Application?
High-volume production may benefit from premium abrasive grains designed for faster cutting and longer disc life, while occasional workshop grinding may require a more cost-effective option.
A Simple Fibre Disc Grit Selection Process
A practical approach is:
Heavy weld or stock removal → 24/36/40 grit
General grinding and blending → 60 grit
Surface refinement → 80 grit
Fine finishing → 120 grit
Not every job requires moving through every grit. Select only the stages needed to achieve the required surface.
Common Fibre Disc Grit Selection Mistakes
Using the wrong grit can increase grinding time and material waste.
Avoid:
- Starting with a fine grit for heavy stock removal
- Using a coarse grit for final finishing
- Skipping surface refinement when finish quality matters
- Applying excessive pressure to compensate for the wrong grit
- Using the same grit for every application
Also ensure the fibre disc and backing pad are suitable for the grinder and application.
FAQs
- What grit fibre disc is best for general metal grinding?
A 60-grit fibre disc is a versatile option for general grinding, blending and moderate material removal.
- Is 36 grit or 60 grit better for weld removal?
36 grit is more aggressive and better suited to heavier weld removal. 60 grit provides more control and is suitable for general grinding and blending.
- Which fibre disc grit gives a smoother finish?
Higher grit numbers such as 80 and 120 produce a finer scratch pattern and are better suited to surface refinement.
- Should I use different grits for one job?
For heavy grinding followed by a smoother finish, moving from a coarse grit to a finer grit can improve the final result.
Final Takeaway
There is no single best fibre disc grit for every metalworking job. Coarse grits such as 24, 36 and 40 are better for aggressive material removal, while 60 grit suits general grinding. For smoother surface refinement, 80 and 120 grit are more appropriate.
Choosing the right grit for each stage can reduce grinding time, improve surface quality and help you get more value from your abrasives. Explore X-Flex fibre discs for metal fabrication to select the right abrasive solution for your grinding application.