Selecting the correct grinding media for any application requires the evaluation of 11 different factors: size, specific gravity, initial feed size, grinding efficiency, pH, discoloration concerns, contamination, availability, cost, size consistency, shape. Union Process has the experience and expertise to help manufacturers identify the best grinding media for their specific needs.

1. The Finer Points of
Grinding Media Selection
Presented by:
www.unionprocess.com

2. 11 Factors to Consider
Selecting the right type of grinding media for any given application
requires the consideration of 11 factors:
• Size
• Specific gravity
• Initial feed size
• Grinding efficiency
• pH
• Discoloration concerns
• Contamination
•Availability
•Cost
• Consistency of size
• Shape

3. Size
Depending on the type of mill and material being processed,
media size can range from 1/8” to 3/8” in diameter.
Small media horizontal mills require a much small diameter,
ranging from .3mm to 2 mm.
Very fine materials with a size
of 2 microns would require
grinding media such as .3mm
Zirconium Oxide Y-TZP.

4. Specific Gravity
The highest density media is tungsten carbide, while any of the
various steel media represent a lower cost dense option.
Lower density media include alumina or steatite/ceramic. Very
viscous slurry requires very dense media that does not float.
Density can have a direct impact on weight, which is an
important consideration when working with a mill that is filled by
volume.
In the case of a 1S Lab Attritor, because of the differences in
their density, 80 pounds of tungsten carbide media would be
required, while only 14 pounds of steatite would be needed for
the same grinding job.

5. Initial Feed Size
Grinding media selection also needs to take the size of the
material being ground into consideration.
Small size media cannot be used to
grind larger material. In the example
pictured at right, the small ceramic
balls would not be appropriate to grind
the larger glass frit – in this case, 3/8”
alumina would be a better choice.
Small material like calcium carbonate requires a small media, like
0.65 mm Zirconium Oxide Y-TZP. Horizontal mills require even
smaller media, ranging in diameter from .2 microns to .3mm.

6. Grinding Efficiency
Very hard media provides a higher level of grinding efficiency
and also allows for longer wear.
pH
Steel media can react differently with acids and slurries – very
acidic types of slurries often require ceramic media.
Discoloration
White materials that need to stay white should be processed with
a light-colored media to reduce chances of discoloration.

7. Contamination
In many cases, it’s important to choose media that won’t cause
contamination, although some countermeasures are available.
For instance, steel media can contaminate the material it’s
grinding, but the contamination can frequently be removed using
magnetic separators.
Because any steel grinding media will contaminate ceramic
material, it’s necessary to use compatible media to avoid this
type of contamination. Some special materials also require very
specific media. One such example is silicon nitride, which must
be ground with silicon nitride media.

8. Availability
The urgency of the grinding project also should be taken into
consideration.
Most steel media are readily available, but more unusual types
of media, like silicon nitride or silicon carbide, may not be in
stock and may require longer lead times.
Proper planning can ensure the right media is available at the
right time.

9. Cost
In a perfect world, grinding media selection would be based
purely on the ability of the media to properly grind the material
at hand.
But it’s not a perfect world, and cost often becomes a factor in
grinding media selection, although certain types of materials
require specific types of media, regardless of the cost.
When cost is a consideration, basic steel media, like through-
hardened carbon steel or a chrome steel, are relatively
inexpensive, while specialty media, like silicon carbide, are
much more costly.

10. Cost (cont’d)
Even within the same media group, there can be wide variances
in cost. For instance, Zirconium Oxide Y-TZP is more expensive
than Rare-Earth Stabilized Zirconium Oxide Y-TZP .
But the initial cost of the media isn’t the whole story – grinding
efficiency also plays a role in the overall cost of media. In the
Zirconium Oxide example above, the more expensive media
also has a much longer wear life, lessening the impact of its
initial cost.
Density is another factor in assessing grinding media costs,
since many mills are filled by volume, and denser media require
more weight to fill the same volume as less dense media.

11. Consistency of Size
Ideally, the selected media for any specific grinding project
should be of consistent size.
But, because of the nature of the manufacturing process,
consistency isn’t always
possible.
In these cases, classification
is sometimes needed to help
ensure the selection of the
best grinding media for the
job at hand.

12. Shape
Grinding media selection also is based on the shape of the
media, as different shapes are more appropriate for different
types of grinding or material.
Satellites are the most common shape and are used
for a variety of applications.
Radius end cylinders are appropriate for
vibratory mills but not Attritors, because the
Attritors’ intensity will break down these types of
media.

13. Shape (cont’d)
Some ceramic media, like Zirconium Oxide Y-TZP, are sold as
perfect spheres.
Specialty media shapes include diagonals, which
are frequently made of stainless steel. This type of
media is less costly than balls and can be preferred
when a tearing motion is required in addition to
grinding.
Balcones are used for specialized applications.

14. The Leader in Grinding Media
As a long-time leader in the production of grinding media,
Union Process, Inc., is the source for the most up-to-date
information on grinding balls and other media, including:
• Our Grinding Media Brochure, which outlines the
specifications on the most common types of media
•A video on “How to Select Grinding Media”
•A Grinding Media Quote Form
Manufacturers in a wide range of industries have come to rely
on our expertise in grinding media production and selection.

15. Contact Us for More Details
Our skilled technical service representatives are always available
for consultation and ready to assist you with the selection of
media that best answer your particular needs.
For assistance, contact Media Sales by calling (330) 929-3333
x228 or by emailing us.
Union Process, Inc.
1925 Akron-Peninsula Road
Akron, Ohio 44313