Choosing Shot Blasting Media: When to Use Steel Shot, Walnut Shell and Other Media
Choosing the right shot blasting media starts with the component and the result you need to achieve – not simply with the abrasive that is most familiar.
Different media behave very differently when they strike a surface. The appropriate choice therefore depends on factors including the condition of the component before blasting, the required finish, component material, geometry and the characteristics of the abrasive itself.
At ActOn Finishing, we recommend considering media type, shape, size, density and hardness when developing a blasting process.
For manufacturers comparing abrasives, one particularly useful distinction is between metallic media such as steel shot and less aggressive media such as walnut shell.
The right choice depends on what you need the media to do.
Start with the Required Result
Before asking “Which blasting media should I use?”, ask:
“What needs to happen to the component?”
For example, does the process need to:
- Clean the surface?
- Remove a coating?
- Remove rust or scale?
- Deburr or de-flash the component?
- Produce a smoother surface?
- Peen the surface?
- Prepare the component for another process?
The answer immediately begins to narrow the media selection.
Abrasive media should then be matched to the starting condition of the component and the finish required after blasting or peening. This is the approach ActOn recommends when specifying blasting media.
When Should You Choose Steel Shot?
Steel shot is a spherical metallic blasting media. Its rounded shape means it impacts and peens the surface rather than producing the cutting action associated with angular abrasives.
Steel shot can be considered for applications including:
- Surface cleaning.
- Shot peening.
- Removing light rust or scale.
- Surface improvement.
- Smooth finishing.
- Bright finishing.
Steel shot is particularly worth considering when:
The application requires a metallic media with a more uniform peening action rather than an aggressive cutting action.
This is an important distinction because the required surface condition should determine the abrasive rather than assuming that all metallic blasting media will produce the same result.
What About Steel Grit?
Steel grit is also an important metallic blasting media, but ActOn has covered its selection, surface profiles and comparison with steel shot in detail in Part 1 of this series.
In simple terms, steel grit is angular and produces a more aggressive cutting action, whereas steel shot is spherical and produces a more uniform peening action.
For detailed guidance on steel grit, read: The Complete Guide to Steel Shot and Grit Blasting.
When Should You Choose Walnut Shell Blasting Media?
Walnut shell provides a very different finishing action from metallic blasting media.
ActOn identifies walnut shell as suitable for removing coatings, cleaning, deburring and de-flashing.
That makes it relevant when the application requires a different level of surface interaction from a metallic abrasive.
Rather than asking whether walnut shell is “better” than steel shot, manufacturers should consider whether its characteristics are more appropriate for the component and required result.
Walnut shell can be considered where the objective includes:
- Cleaning.
- Coating removal.
- Deburring.
- De-flashing.
This makes walnut shell an important option within a broader abrasive-media selection process rather than simply an alternative version of steel media.
Steel Shot vs Walnut Shell: What’s the Difference?
This should be the core comparison.
| Selection factor | Steel shot | Walnut shell |
|---|---|---|
| Media category | Metallic | Organic |
| Media characteristic | Spherical steel particles | Hard, fibrous natural media |
| Typical action | Impact / peening | Medium abrasive action |
| ActOn applications | Cleaning, peening, light rust/scale removal, surface improvement and smooth finishing | Coating removal, cleaning, deburring and de-flashing |
| When to investigate it | Where metallic media and controlled peening/surface treatment are required | Where cleaning or material removal needs a different action from metallic blasting media |
Steel shot and walnut shell are not substitutes selected on price alone. They have different physical characteristics and are suited to different finishing objectives.
Steel Shot, Walnut Shell: A Selection Framework
| Start with | Ask |
|---|---|
| Process | Is this a blasting, peening, cleaning, polishing or drying application? |
| Starting condition | What contamination, coating, burr, scale or surface condition needs addressing? |
| Required result | Do you need cleaning, peening, coating removal, deburring, polishing or another finish? |
| Component | What material is the component manufactured from and how sensitive is its surface? |
| Media characteristics | What type, shape, size, density and hardness are appropriate? |
| Validation | Does the selected media deliver the required result on the actual component? |
For shot blasting specifically, steel shot may be appropriate where a metallic spherical media and peening action are required, while walnut shell can provide an alternative for applications including coating removal, cleaning, deburring and de-flashing.
Why Media Size Matters Too
Media size influences how the abrasive interacts with the component and should therefore be selected according to the component, its geometry and the required finish.
Don’t Select Blasting Media on Abrasive Type Alone
The most important takeaway from this guide is that there is no universal “best” blasting media.
The right choice depends on:
- Starting surface condition.
- Required finish.
- Component material.
- Component geometry.
- Blasting or finishing process.
- Media characteristics.
- Production requirements.
Choosing media based only on whether it is steel, walnut or another abrasive risks overlooking the variables that actually determine the finished surface.
This is why process development and testing are so important.
FAQs
1. How do I choose the right shot blasting media?
Start with the condition of the component before blasting and the finish required afterwards. Then consider media type, shape, size, density and hardness, alongside the component material and process requirements. ActOn recommends considering these variables when selecting abrasive blasting media.
2. When should I use steel shot blasting material?
Steel shot can be considered for applications requiring a spherical metallic media and a peening rather than aggressive cutting action. Applications can include cleaning, shot peening, light rust or scale removal, surface improvement and smooth finishing.
3. What is walnut shell blasting media used for?
ActOn identifies walnut shell blasting media for applications including removing coatings, cleaning, deburring and de-flashing.
4. Can ActOn help me select blasting media for my components?
Yes. Media selection should be based on the component’s starting condition, required finish and the relevant media characteristics. A process trial can help determine the appropriate media and operating parameters for the actual component.
Test the Media on Your Components
At ActOn Finishing, media selection can be developed around the actual component and required result.
Rather than assuming that a particular steel shot blasting material, walnut shell or other abrasive will provide the desired outcome, the process can be tested to determine the appropriate media and operating parameters.
Speak to ActOn’s team about your component, its current condition and the finish you need to achieve.
Explore ActOn’s Shot Blasting Media
Call: +44 (0) 24 7646 6914
Email: sales@acton-finishing.co.uk