Every load of cracked grain costs you twice. You lose weight at the elevator through dockage, and if the damage runs high enough, the whole load drops a grade. In a bad year, two or three extra points of broken kernels can shave more off your check than fuel and labor combined.

The frustrating part is that most grain damage is not a broken part. It is settings that were close enough last week, in a different field, with a different hybrid, and nobody touched them. Grain that came through clean on Monday can start getting hammered by Thursday simply because the crop dried down or the ground speed crept up.

This guide walks through the usual suspects in the order you will actually find them in the field, starting with the two adjustments that cause the majority of problems.

First, make sure it is machine damage

Before you start turning wrenches, take a minute to confirm the cracking is happening inside the combine. Hail, frost, insects, or a desiccant applied too late can all crack grain before the header even touches it.

Scoop a sample from the grain tank and spread it on a clean surface. Then walk behind the combine and pick up a few heads, cobs, or pods that went through. If the grain on the ground is already cracked, the problem started before harvest. If the grain on the ground is intact but the tank sample is cracked, the machine is doing it.

One more check: look at where the damage sits in the load. If most of the cracked grain is in the center and the edges look clean, the return system may be overworking. If it is evenly mixed through, the threshing area is the likely source.

Cause 1: Cylinder or rotor speed too high

This is the number one cause of cracked grain, and the easiest to fix. The cylinder or rotor beats grain off the head or cob. Run it fast enough to thresh, and no faster. Every RPM beyond that point adds impact energy with nowhere to go except into the kernels.

The telltale sign is a tank sample full of finely cracked grain and powder, often with straw beaten short and fluffy. You may also see grain going out the back with the chaff because the cleaning shoe cannot keep up with the flood of fine material.

Start at the low end of the recommended speed for your crop and work up. A lot of operators do the opposite: they start fast to make sure nothing goes out unthreshed, then never back off. You want the slowest speed that still shells the grain clean. Check a sample, drop the speed 50 RPM, and check again. Keep going until unthreshed grain starts going out the back, then nudge it up one step.

Cause 2: Concave clearance too tight

The concave is the curved grate sitting under the cylinder. The gap between the two, wider at the front and narrower at the back, controls how hard the crop gets rubbed. Close that gap too far and every cob, pod, or head gets crushed along with the grain.

Damage from a tight concave looks a little different from high-speed damage. You will see split kernels and crushed cob or pod pieces mixed through the sample, rather than the fine powder you get from pure impact. In corn, whole cobs may come through broken into short sections.

Open the concave slightly, a quarter turn at a time, and run another sample. You are looking for the widest gap that still leaves the cobs or heads clean. If whole, unthreshed heads start going out the back, you have gone too far.

Speed and clearance work as a pair

Here is where a lot of operators get turned around. Cylinder speed and concave clearance are not independent dials. They compensate for each other, and they can fight each other.

If you open the concave, you may need a touch more cylinder speed to hold the same threshing action. If you slow the cylinder, you may need to close the concave slightly. The old rule still holds: set the speed first, then adjust the clearance to match. If you are seeing cracked grain, reduce speed before you open the concave. Dropping speed usually fixes it without costing you threshing performance.

Write down what works. A pocket notebook with the crop, hybrid, moisture, speed, and clearance for each field will save you half a day of guessing next season.

Cause 3: Worn threshing parts

Settings will not save you if the hardware is worn out. Rasp bars wear smooth. Concave wires get thin and rounded. On rotary machines, the rotor rasp bars and concave bars both wear down. As the edges round off, the machine loses its ability to rub grain free, so the natural response is to speed up or close the gap, which cracks more grain while still not threshing cleanly.

Shut down, lock out the power, and open the stone trap or inspection cover. Run your hand over the rasp bars. If they are rounded and polished instead of sharp-edged, they are finished. Check the concave for bent or broken wires and for thin spots where the crop has been wearing through. Measure the clearance evenly across the full width: a concave that is tight on one side and open on the other will crack grain on the tight side while throwing unthreshed grain out the open side.

Replace parts in sets. One new rasp bar next to three worn ones creates an uneven gap and makes the problem worse.

Cause 4: Wrong concave for the crop

A concave built for corn is too open for wheat or soybeans. Large round wires or wide-spaced bars let small grain and thin pods pass through without being properly threshed, so you compensate by tightening down, and then you crack grain.

If you run multiple crops, change the concave, or the concave covers and inserts depending on your machine, when you change crops. It is a short job that saves more than that in lost grain. Some operators run a multi-crop or small-wire concave year-round and accept a small capacity penalty in corn rather than risk forgetting to swap.

Cause 5: Overloading the machine

Ground speed is a threshing setting too. Push too much crop through the cylinder and the material packs into the concave gap instead of rolling through. Grain gets trapped against the concave and ground against it. You will see cracked grain, uneven threshing, and a choppy note from the separator.

The fix is usually to slow down, especially in heavy or weedy spots, laid crop, or when cutting uphill. Keep the header just as low as you need it: excess straw through the machine is excess material the threshing and cleaning systems have to process. If you are consistently overloaded in a standing crop, you may need a wider concave setting or a different rotor configuration rather than more speed.

Cause 6: Harvesting too dry

Brittle grain cracks easily. There is not much you can do about the weather, but you can adjust around it.

Wheat combined below roughly 12 percent moisture, soybeans under 12, or corn that has dried down past 15 percent will crack at settings that were fine a few days earlier. If you are in dry, brittle crop, drop the cylinder or rotor speed 10 to 15 percent below your usual starting point and open the concave slightly. It can also help to combine later in the day or at night, when humidity puts a little moisture back into the grain, rather than running through the driest part of the afternoon.

Cause 7: Cleaning shoe and fan

Not all damage happens at the cylinder. A cleaning fan running too fast can physically blast grain against the sieves and the sides of the shoe, especially with light seed like wheat or oats. The chaffer and sieve settings matter too. Close them down too far and grain gets trapped and recirculated instead of falling through to the clean-grain auger.

If you are seeing cracked grain but the threshing sample looks good, check the fan. Reduce air until grain starts to carry over with the chaff, then bring it back up just enough. Open the chaffer so grain falls through easily but coarse trash stays on top. Set the lower sieve so clean grain passes through and the tailings elevator carries back only unthreshed material, not whole, clean kernels.

Cause 8: The return (tailings) system

The tailings elevator sends unthreshed grain back to the cylinder for a second pass. When it is carrying back mostly clean grain, because the sieves are too closed or the fan is too low, that grain gets threshed twice. The second pass is where a lot of hidden cracking happens.

Reach into the tailings return at the inspection port, with the machine shut down and locked out. You should see mostly unthreshed heads, pods, or cobs. If it is mostly clean grain, your shoe settings are wrong, not your cylinder. Fix the shoe and the cracking will often drop without touching the threshing settings.

Cause 9: Augers and elevators

Grain can crack after threshing on its way to the tank. Worn auger flighting with sharp edges, a damaged clean-grain elevator chain, or an auger adjusted too tight can all shear kernels. This kind of damage usually shows up as a steady percentage of cracked grain regardless of your threshing settings. If you change speed and clearance and the crack percentage barely moves, start looking downstream.

Check the clean-grain and tank augers for sharp or bent flighting, and inspect the elevator paddles and chain for damage. Make sure augers are not over-tightened against their housings.

A field adjustment sequence that works

When you are standing in the field with a sample full of cracked grain, do not start changing everything at once. You will never know what fixed it. Follow this order:

1. Confirm the damage is from the machine, not the field.

2. Check the tailings return. If it is full of clean grain, fix the shoe first.

3. Reduce cylinder or rotor speed 50 RPM and run a sample. Repeat until you see improvement or unthreshed grain starts going out the back.

4. If damage persists, open the concave a quarter turn and test again.

5. Check the fan and sieve settings.

6. Inspect for worn parts if settings do not bring the damage down.

7. Slow your ground speed if the machine is overloading.

Change one thing at a time and run at least 50 yards before checking the sample. Small adjustments, tested one at a time, beat a full reset every time.

Starting points by crop

These are rough starting points, not targets. Your operator's manual is the authority for your specific machine, and conditions shift with hybrid, moisture, and straw load. Always start low and work up.

Quick maintenance checklist

Before you blame the settings, walk through these once a season:

• Rasp bars and concave bars: sharp, not rounded; replaced in sets.

• Concave clearance: even across the full width.

• Wires and grates: no bent, broken, or thin spots.

• Auger flighting: no sharp edges or bends; proper clearance in the housing.

• Elevator chains and paddles: not loose, cracked, or missing.

• Sieves and chaffer: clean, no bent louvers; openings move freely.

• Fan: no broken blades or buildup throwing it off balance.

• Belts and drives: tight enough that cylinder speed holds under load.

When it is not the settings

If you have worked through speed, clearance, fan, and sieves and you are still seeing cracked grain, you are likely looking at one of two things: worn hardware that needs replacing, or a machine too small for the crop you are asking it to eat. A worn combine cannot be tuned out of cracked grain, and pushing an undersized machine past its capacity will crack grain no matter how careful you are with the dials.

That is the point worth raising with your dealer or the manufacturer. If you are replacing concaves or looking at a machine better matched to your acres and crops, a conversation before next harvest beats a season of dockage.

Most grain damage is preventable, and most of it traces back to the same two adjustments. Keep the speed as low as you can, set the concave to match, check the sample often, and write down what works. The combines that consistently bring in clean grain are not the fanciest ones. They are the ones somebody is paying attention to.