my chainsaw makes a high-pitched whining or grinding noise when it runs, doesn't sound right.

Diagnosis

The high-pitched whining or grinding noise in the DeWalt DCCS620B is typically caused by one of two mechanical failures: acute friction due to a lubrication failure or a failing drive sprocket bearing. Because this is a brushless motor system, a "whine" that increases in pitch as the chain speeds up usually indicates that the chain is running "dry," causing metal-on-metal friction between the guide rail and the drive links. If the sound is more of a rhythmic grinding or a "shuddering" noise, the issue is likely located at the nose sprocket (the tip of the bar) where the small bearings have either seized or collected debris, forcing the chain to grind against the sprocket wheel. To confirm the cause, perform a "splatter test." Start the saw and lightly rev the trigger while pointing the tip of the bar toward a clean piece of cardboard or light-colored wood. If you do not see a fine mist of oil spraying onto the surface, your automatic oiler is clogged or empty, and the whining noise is the result of the chain overheating and dragging across the bar. If oil is spraying but the noise persists and feels like a vibration in the handle, the nose sprocket is the culprit.

How to Fix It

Follow these steps to resolve lubrication and sprocket issues:

1. Immediate Shutdown: Remove the 20V Max battery immediately to prevent the motor from overheating or stripping the drive gear.
2. Oil Reservoir Audit: Open the bar oil cap. If the oil level is below the halfway mark, fill it to the brim using a high-quality tackifying bar and chain oil. Do not use motor oil or WD-40, as these lack the viscosity to cling to the bar at high RPMs.
3. Clear the Oil Port: Locate the small circular oiling hole where the bar meets the saw housing. Use a thin piece of wire or a compressed air canister to clear any sawdust or resin buildup blocking the port. This is the most common cause of "dry" running on the DCCS620B.
4. Nose Sprocket Inspection: Use a small pick to remove any packed sawdust from the tip of the bar. If the nose sprocket does not spin freely by hand, use a can of penetrating oil to loosen the bearing.
5. Chain Tension Adjustment: Loosen the bar nuts slightly and turn the tensioning knob until the chain is snug against the bar but can still be pulled along the rail by hand. An overly tight chain creates a high-pitched "singing" noise due to excessive tension on the motor.
6. Verification: Reinsert the battery and run the saw for 30 seconds. Check for the oil spray again to ensure the lubrication cycle is active.

If That Didn't Work

• Replace the Guide Bar: If the bar has developed a "burr" or a sharp ridge along the rails, the chain will grind against the metal regardless of how much oil you use. Inspect the edges of the bar; if they are flared or jagged, replace the bar entirely.
• Swap the Chain: A damaged drive link (the part of the chain that fits into the bar groove) can cause a rhythmic grinding noise. Replace the chain with a new, sharpened 16-inch chain to see if the noise disappears.
• Inspect the Drive Sprocket: Remove the side cover and check the main drive sprocket for worn teeth or debris. If the sprocket teeth are rounded off or chipped, they will create a grinding sound as they engage the chain.
• Battery Check: In rare cases, a failing battery cell can cause the brushless controller to "hunt" for power, creating an electronic whining sound. Swap the battery with a known-good 5.0Ah or higher XR battery to rule out electrical oscillation.

Heads Up

• Oil Every Time: Never run the saw without checking the oil reservoir. Running a chain dry for even two minutes can permanently warp the guide bar and ruin the chain's temper.
• Avoid Over-Tensioning: The DCCS620B is a high-torque tool; if the chain is too tight, you risk snapping the drive sprocket or burning out the motor controller.
• Clean the Air Vent: Dust buildup around the motor vents can cause the fan to whine. Use compressed air to blow out the motor housing every 5-10 cuts.
• Use Proper Lubricants: Only use bar-specific oil. Using thinner oils will result in the oil being flung off the bar before it reaches the tip, leading to the same grinding noise you are currently experiencing.