my saw is making a horrible grinding noise and sparks are coming out near the blade when i try to cut.

Diagnosis

The combination of a grinding noise and visible sparks near the blade on the DCS570B typically indicates a catastrophic failure of the arbor bearing or a severe misalignment of the motor's armature. When the bearings fail, the arbor shaft begins to oscillate or "walk" during rotation. This creates an eccentric orbit that forces the internal rotor to make physical contact with the stator windings or the motor housing, resulting in the grinding sound and the electrical arcing (sparks) you see. Alternatively, this can be caused by a bent arbor shaft resulting from a "kickback" event or a crashed cut. If the shaft is bent even by a fraction of a millimeter, the blade will wobble, causing the internal centrifugal components to strike the housing. You can confirm this by removing the battery and spinning the blade by hand; if you feel a "catch" or a rhythmic vibration, or if you see the blade flange oscillating horizontally, the arbor assembly is compromised. If the sparks are coming from the rear of the motor rather than the blade area, it is more likely a worn carbon brush assembly, but sparks near the blade always point to mechanical failure in the drive train.

How to Fix It

Because the DCS570B uses a high-density integrated motor and gear housing, you cannot simply replace a single bearing. You must replace the entire motor and arbor assembly to ensure the tool remains safe and calibrated.

1. Safety First: Remove the 20V Max battery immediately. Unplug the tool from any power source and ensure the blade is locked in the "down" position.
2. Blade Removal: Use the provided wrench to loosen the arbor bolt. Remove the outer flange and the circular saw blade. Inspect the flange for any signs of scoring or heat discoloration.
3. Housing Disassembly: Using a T15 Torx driver, remove the exterior housing screws. Carefully peel back the plastic casing, taking note of the wire routing for the trigger switch to avoid pinching them during reassembly.
4. Motor Extraction: Disconnect the electrical leads from the trigger assembly. Unscrew the mounting bolts that secure the motor/gear assembly to the base plate. Carefully lift the motor unit out of the chassis.
5. Component Replacement: Install a genuine DeWalt replacement motor and arbor assembly (Part No. DCS570-Motor-Assy). Ensure the unit seats fully into the base plate grooves before tightening the mounting bolts to 4-6 Nm of torque.
6. Reassembly: Route the wires back through the chassis guides and snap the housing back into place. Tighten the T15 screws firmly but do not over-torque, as the plastic housing can crack.
7. Testing: Reinstall the blade and perform a "dry spin" without a workpiece to ensure the grinding noise has ceased and no sparks are present.

If That Didn't Work

• Check the Blade Flange: If the motor is fine, a warped outer flange can cause the blade to tilt, creating a grinding sound against the lower guard. Replace the outer flange and tighten the arbor bolt to the specified torque to ensure the blade is perfectly perpendicular to the shaft.
• Inspect the Lower Guard Spring: Sometimes the grinding noise isn't internal, but the lower guard is rubbing against the blade due to a bent pivot arm or a weakened spring. Inspect the guard for any scratches or metal shavings; if found, replace the guard assembly.
• Debris Clearance: Use compressed air to blow out the motor vents. In some cases, a large piece of metallic debris or a stray screw can enter the motor housing, causing a grinding sound and sparks as it bounces off the armature.
• Battery Voltage Drop: If the sparks are exclusively coming from the motor vents during high-load cuts, your battery may be failing to provide consistent voltage, causing the motor to "stutter" and arc. Test the saw with a fresh, fully charged 5.0Ah or higher battery.

Heads Up

• Avoid "Forcing" Cuts: Grinding often starts when the user pushes the saw too hard into the wood. Let the RPMs do the work; if the motor slows down significantly, reduce your feed rate.
• Blade Quality: Always use a high-quality, sharp carbide blade. Dull blades increase the load on the arbor bearings, leading to premature wear and eventual failure.
• Clean the Base: Regularly clean the sawdust from the base plate and motor vents. Accumulated dust can overheat the bearings, causing the lubricant to break down and the metal to grind.
• Warning: Never attempt to lubricate the motor bearings with WD-40 or household oil. These are sealed bearings; adding external lubricants can attract conductive dust and cause a short circuit.