When it comes to hammer mill screens, most feed mill operators can tell you exactly which one they use, but are unsure of the particle size distribution it produces. Particle sizes in feed are often measured in average micron while hammermill screen sizes are often labeled using standardized screen numbers like #6, #8, and #10.These numbers are based on how many passages or holes the screen has per inch. For example a #6 screen has 6 passages per inch or each hole is roughly ⅙” in size. While these numbers are widely used across the industry, the exact micron measurement can vary slightly depending on the machine variables such as CFM of the air sweep or hammer speed. But what happens when it’s time to compare that hammer mill screen to a roller mill’s performance? Things get murky. Hammer mill screens don’t translate cleanly into micron size, and that can leave operations in the dark when evaluating particle size control.
This guide clears up the confusion. We’ll walk through how hammer mill screens size particles, what microns actually measure, and why shifting your thinking to microns (and roller mills) could give your operation a serious edge.
Why Your Screen Size Might Be Misleading
Hammer mills crush grain with high-speed steel hammers, breaking it down until it’s small enough to pass through a sizing screen. The screen determines the maximum particle size, but not the average or the spread. A #8 hammer mill screen might seem to give you an ideal grind, but what does that mean in terms of particle size measurement?
Unfortunately, not much.
The result? Inconsistent output, more dust and fines, and a lot of guesswork when matching grind size to your process needs. Often time compromises are made in particle size by having to increase the amount of coarser material to counteract the fines. This makes the situation worse as you have more particles that are not in the ideal size range.
Micron Size: A Deeper Look
In feed particle size is measured as distribution and the geometric mean (average) of the distribution is what the industry looks at. In the feed industry it has standardized around the metric measurement of microns (µm) One micron equals one-millionth of a meter, and when we use this measurement standard, we can compare apples to apples, no matter the equipment.
Here’s a look at the screen size to micron conversion for corn, a common livestock feed.
Approximate Screen Size to Micron Conversion for Corn (Typical Hammer Mill Setup)
| Screen Size (inches) | Approx. Micron Size (µm) | Use Case |
|---|---|---|
| 3/32” (2.38 mm) | ~350–500 µm | Dairy |
| 1/8″ (3.18 mm) | ~500–800 µm | Swine finisher feed |
| 3/16″ (4.76 mm) | ~900–1,000 µm | Swine sow feed, poultry layers and broiler |
| 1/4″ (6.35 mm) | ~1,200–1,400 µm | Turkeys |
| 3/8″ (9.53 mm) | ~1,600–1,800 µm | Ruminant feed |
| 1/2″ (12.7 mm) | ~2,000+ µm | Coarse feeds, scratch grain |
Hammer mill particle size depends on the material, moisture content, machine speed, and wear on the hammers or screen. And because screen size only sets a maximum limit, a wide range of over- and undersized particles can still pass through.
Why Roller Mills Offer Superior Particle Size Control
Roller mills offer consistent, micron-level control that hammer mills can’t match. Here’s where the switch to roller mills pays off:
1. More Uniform Particle Size
Roller mills use shearing, not impact. That results in tighter control and a narrower particle size spread. You get less dust, fewer fines, and more predictable processing.
2. Better Yield, Less Waste
With more uniform particles, roller mills reduce product loss and improve feed flow and performance throughout the system, resulting in better pellet quality, smoother mixing, and optimized digestibility.
3. More Accurate Targeting
Particle size distribution targets enable you to adjust your process to meet exact requirements. No more guessing based on screen numbers, hammer speed, and airflow.
4. Energy and Material Efficiency
Roller mills achieve the desired particle size using less energy, while causing less material degradation.
In short, it’s not just about grind—it’s about control, precision, and performance.
Making the Switch with RMS
Transitioning from a hammer mill to roller mill setup doesn’t have to be complicated. At RMS, we simplify the process by helping customers move beyond screen size and focus on the real question: What particle size do you actually need vs what have you been getting?
Once we have a target particle size, we can select the appropriate roller mill, adjust the gap settings, and even test your material to ensure you’re getting exactly what you expect. We’ve helped countless operators move from hammer mills to roller mills with minimal disruption and maximum long-term gain.
Ready to Join The Industry Shift To Quality?
As the feed industry shifts to demanding more quality, roller mills are a clear cut choice. RMS can help you understand the impact on your business and makes it easy to make the switch.
Let’s discuss your particle size goals and how we can assist you in replacing your hammer mill with precision-focused roller mills.
