How to Read Abrasive Mesh and Grit Designation Charts

If you have ever looked at a specification for aluminum oxide, garnet, or silicon carbide and seen labels like "F80," "80 grit," or "80 mesh," you have encountered the core confusion in abrasive sizing. These numbers are not interchangeable, and assuming they are can lead to a profile that is too deep, too shallow, or completely inconsistent. This article is written for industrial buyers, maintenance technicians, and engineers who need to decode abrasive sizing systems—particularly the mesh scale, the grit scale, and the relationship between them—before placing an order or writing a blast specification.

By the end, you will understand what mesh and grit numbers actually measure, how to read a typical abrasive mesh size chart, when to trust one numbering system over the other, and what practical checks to apply before committing to a media grade.

An abrasive mesh size chart is a reference table that links a "mesh number" to the physical particle size of the abrasive grain. The mesh number tells you how many openings per linear inch exist in the sieve screen through which the particles were sorted. A higher mesh number means a finer screen and therefore smaller particles; a lower mesh number means a coarser screen and larger particles.

For example, a particle that passes through a 30-mesh screen but is retained on a 40-mesh screen is typically described as 30/40 mesh. In practice, many industrial charts simplify this to a single number that represents the nominal sieve size, and the actual particle size distribution is controlled by a standard such as ASTM E11 (test sieves) or ISO 565.

A typical abrasive mesh size chart will show:

• Mesh number (e.g., 24, 36, 60, 80, 120)
• Approximate particle size in microns or thousandths of an inch
• A corresponding grit designation where applicable

The terms "mesh" and "grit" are often used as if they mean the same thing, but they originate from different sizing philosophies. Understanding the distinction is the first step in reading any product label correctly.

Mesh Sizing

Mesh sizing is defined by sieving. The number refers to the count of wires per inch in a square sieve screen. It is a direct physical measurement: a 60-mesh screen has 60 wires per inch, leaving smaller openings than a 30-mesh screen. Mesh sizing is common for softer or more friable abrasives like garnet, silica sand (where still permitted), and some grades of aluminum oxide used in blasting.

Key points about mesh sizing:

• It describes the screen that the particles passed through, not the particle shape.
• It works well for blocky or irregular grains.
• Two different abrasives with the same mesh number can behave differently because of differences in density, shape, and friability.

Grit Sizing (SAE and ISO Grit)

Grit sizing, by contrast, is defined by industry standards that specify a controlled particle size distribution. The most frequently encountered standards in industrial blasting are:

• SAE J444 (commonly called SAE grit) – used primarily for metallic abrasives like steel grit and cast iron grit. An SAE grit designation such as G40 or G25 refers to a specific screen distribution defined by the standard.
• ISO 11126 / ISO 11127 and the older FEPA F-series – used for non-metallic abrasives such as aluminum oxide and silicon carbide. An "F80" designation under FEPA means a defined size band, not simply "passed through an 80-mesh screen."

The critical point: an SAE G40 steel grit is not the same size as a 40-mesh garnet particle. The numbering systems are not directly transferable, which is why reading the designation chart for the specific abrasive type matters.

Why the Confusion Persists

The confusion exists because some non-metallic abrasive suppliers label their products with a single number that looks like a grit designation but is actually a nominal mesh size. A product labeled "80 grit garnet" may in reality be an 80-mesh garnet. Without checking the accompanying micron range or the standard referenced, the buyer cannot be certain what they are getting.

Abrasive particle size directly controls:

• Surface profile depth – larger particles cut deeper peaks and valleys; smaller particles produce a finer profile.
• Coverage rate – finer abrasives tend to cover more square area per kilogram but cut more slowly.
• Media consumption and dust generation – undersized particles can shatter on impact, creating excessive dust without useful work.
• Nozzle and equipment wear – abrasive that is coarser than the system is designed for accelerates wear on blast nozzles, hoses, and metering valves.

Selecting the wrong size can result in a profile that fails to meet the specified standard (such as SSPC SP10 or SA 2.5), leading to coating adhesion failure and costly rework.

Mesh sizing is most reliable when:

• The abrasive is a natural or crushed mineral with irregular particle shapes (garnet, crushed glass, some aluminum oxides).
• The supplier provides a clear micron range alongside the mesh number.
• The application does not demand extremely tight particle distribution control—typical for general blast cleaning and rust removal.

Mesh sizing alone is a poor fit when:

• You are specifying metallic abrasives (steel grit, steel shot, cast iron grit). These should always be ordered by SAE grit designation or an equivalent standard.
• The surface preparation specification calls for a tightly controlled profile range, such as 50–75 microns for a high-performance coating. In these cases, request the actual particle size distribution data from the supplier.
• You are comparing two different abrasive types. A 36-mesh garnet and a 36-mesh aluminum oxide will not produce identical results because of differences in hardness, density, and particle shape.

When you encounter an abrasive mesh size chart on a product page or technical data sheet, approach it systematically:

1. Identify the abrasive type. The chart should state whether it applies to garnet, aluminum oxide, silicon carbide, or another media. Do not use a garnet chart to interpret a steel grit designation.

2. Locate the mesh number column. This is your entry point if the product label uses a mesh designation (e.g., 30/60 mesh).

3. Find the corresponding micron range. Reputable charts will show the approximate particle size in microns (µm) or mils (thousandths of an inch). This is the most objective measure and allows comparison across different sizing systems.

4. Check for a grit cross-reference column. Some charts include an approximate FEPA F-grade or ANSI grit equivalent. Treat this as a rough guide only—confirm against the actual specification if the application is critical.

5. Note the application guidance if provided. Many charts suggest typical uses (e.g., "60 mesh – light rust removal, anchor profile 25–40 µm"). Use this as a starting point, not a substitute for trial on your specific substrate.

Example Walkthrough

Suppose a chart shows the following row:

This tells you that a 36-mesh abrasive will pass particles roughly in the 500–600 micron range. If your specification requires a surface profile of 75–100 microns, this abrasive is likely too coarse. You would look further down the chart—perhaps at 60 or 80 mesh—to find a particle size that can produce the required profile without exceeding it.

Mistake 1: Assuming Mesh Number Equals Grit Number

This is the most frequent error. A buyer sees "80" on a garnet bag and assumes it is equivalent to an SAE G80 steel grit. In reality, SAE G80 is a much finer particle than 80-mesh garnet. Always verify which sizing system the number belongs to.

Mistake 2: Ignoring the Particle Size Distribution

A mesh number gives a nominal sieve size, but real abrasive contains a distribution of particle sizes. Two different 60-mesh abrasives can have different proportions of fines and oversize particles, affecting performance. When consistency matters, ask for the full sieve analysis.

Mistake 3: Selecting by Mesh Number Without Considering Hardness

A finer mesh of a soft abrasive may break down too quickly to achieve the desired profile. Conversely, a coarser mesh of a very hard abrasive like aluminum oxide may cut deeper than expected. Mesh size is only one variable; hardness, shape, and impact energy all matter.

Mistake 4: Using a Single Number When a Range Is Specified

Some abrasives are sold as a range (e.g., 30/60 mesh). This means the particles pass a 30-mesh screen and are retained on a 60-mesh screen. Ordering "30 mesh" when the specification calls for 30/60 mesh will give you a different product entirely—one with a wider or narrower distribution depending on the supplier's interpretation.

When you need to choose an abrasive size for a specific job, follow this sequence:

1. Start with the surface preparation specification. What profile depth is required? What standard applies (SSPC, ISO, NACE)? The specification should guide your particle size range.

2. Identify the abrasive type you intend to use. Metallic or non-metallic? This determines whether you work from an SAE grit chart, an ISO/FEPA chart, or a mesh chart.

3. Consult the appropriate abrasive mesh size chart or grit designation table. Match the required profile to the recommended particle size range in microns, then find the corresponding mesh or grit number.

4. Verify with the supplier. Ask for the actual micron range and the standard to which the abrasive is sized. A reliable supplier will provide this without hesitation.

5. Run a test patch if possible. No chart replaces a quick blast test on the actual substrate with the actual equipment. Measure the resulting profile and adjust if needed.

Abrasive sizing systems are not complicated once you recognize that mesh and grit are different languages describing the same physical property: particle size. Mesh numbers refer to sieve screens; grit numbers refer to standardized distribution bands defined by SAE, ISO, or FEPA. The key to reading any abrasive mesh size chart is to focus on the micron equivalent, understand which sizing system applies to your abrasive type, and never assume that a number in one system means the same thing in another.

For new buyers and technicians, the safest approach is to work from the required surface profile backward: determine the micron range you need, consult the correct chart for your abrasive type, and confirm the specification with your supplier before ordering in volume.