Question 1

the bit keeps falling out of my dewalt impact driver, the magnetic holder doesn't seem strong anymore.

Accepted Answer

DIAGNOSIS The magnet in the anvil has lost its pull. This is often caused by metal shavings coating it (acting as a barrier) or the magnet itself getting physically damaged or demagnetized from repeated impacts. FIX Clean the magnet. Remove any bit. Look into the hex collet—you'll see a silver magnetic ring at the bottom. Use a strong magnet or a piece of sticky tape (like duct tape) to carefully lift out any accumulated tiny metal flakes. Then, wipe the magnet surface with a clean cloth. For a weak magnet, you can try to 'recharge' it by holding a much stronger neodymium magnet against it for a few minutes, though this isn't always permanent. IF THAT DIDN'T WORK The magnet is a press-fit part. If it's cracked or completely lost its strength, the entire anvil assembly needs to be replaced to fix the magnetic hold. HEADS UP The magnet is primarily for convenience, not retention. The ball detent lock is what's supposed to hold the bit in under load. If bits are physically launching out, that's a detent issue, not a magnet issue.

Question 2

my impact driver gets really hot right behind the chuck after just a few screws, is that normal?

Accepted Answer

DIAGNOSIS Some heat is normal—that's the motor and gearbox area. But excessive heat quickly usually means you're overworking it or there's a lubrication issue. FIX First, check your technique. Are you applying too much forward pressure? Let the impact mechanism do the work; you just need to guide it. Pushing too hard creates friction and heat. Second, ensure you're using the right bit. A worn or low-quality bit will slip in the screw head, creating massive friction and heat that transfers back into the chuck and anvil. IF THAT DIDN'T WORK If it's getting hot during normal, easy use, the grease in the gearbox might have degraded or leaked out. This requires disassembly to regrease, which isn't a simple user service. HEADS UP If the tool is too hot to touch or you smell burning, stop immediately and let it cool. Continuous overheating can permanently damage the motor windings or plastic components. This model doesn't have a thermal overload protection circuit like some larger tools.

Question 3

the forward/reverse button on my dcf787 is super stiff and hard to slide with one thumb.

Accepted Answer

DIAGNOSIS Dirt, sawdust, or dry plastic is gumming up the slide mechanism. It's a common issue because the button isn't fully sealed. FIX With the battery removed, work the button back and forth vigorously dozens of times. This can help loosen packed debris. Then, take a can of electrical contact cleaner (not WD-40). Spray a very small amount into the seams around the sliding button. Immediately work the button back and forth again to work the cleaner in and dissolve any gunk. Wipe away any excess. IF THAT DIDN'T WORK If it's physically misaligned or cracked, the button housing might be damaged. Inspect it for any visible cracks or deformation that could be causing it to bind on the tool's body. HEADS UP Don't force it or you could break the internal plastic switch. If contact cleaner doesn't free it up, the switch assembly is a sealed unit and requires disassembly or professional repair to replace.

Question 4

how do you clean out the chuck on a dewalt impact? mine is jammed full of sawdust and won't hold bits tight.

Accepted Answer

DIAGNOSIS Sawdust and debris are packed into the 1/4" hex collet, preventing the spring and ball detent from gripping the bit properly. FIX You need to physically dig it out. First, use a small pick, a stiff wire (like a straightened paperclip), or a small flat-head screwdriver to scrape out the big chunks from the collet opening. Then, get a can of compressed air and blast it directly into the chuck from multiple angles. Rotate the anvil (the part that holds the bit) by hand while blowing to clear all sides. Finally, put a drop of light machine oil (like 3-in-1 oil) on a clean bit, insert and remove it a few times to lubricate the ball bearing mechanism. IF THAT DIDN'T WORK If bits are still slipping or the release collar feels gritty and stuck, the internal spring might be damaged or the collet assembly might need replacement. That's a parts fix. HEADS UP Never use water or solvent cleaners. They can wash debris further into the gearbox. Doing a quick blow-out with air after particularly dusty jobs is the best preventative maintenance.

Question 5

impact driver seems weak, it struggles to drive 3 inch screws into pine and the battery dies super fast.

Accepted Answer

DIAGNOSIS You're likely using the wrong battery. The DCF787 is a compact driver, designed for speed and finesse, not maximum torque. Pairing it with a small, low-capacity battery (like the 1.3Ah or 2Ah) will cause it to sag under load and deplete quickly. FIX Get a bigger, higher-output battery. Use a DeWalt 5.0Ah 20V MAX battery or larger. The higher amp-hour (Ah) rating means more capacity, and the cells inside can deliver more sustained current, which gives the motor the power it needs under heavy load. You'll notice a huge difference in both runtime and perceived power. IF THAT DIDN'T WORK If you're already using a 5.0Ah+ battery and it's still weak, check the speed setting. The DCF787 has a variable speed trigger, but no separate high/low gear. Make sure you're pulling the trigger fully for max RPM. Also, use impact-rated screws; standard wood screws have more friction. HEADS UP This model isn't meant for lag bolts or heavy structural framing. If you're constantly driving long, thick screws, you've outgrown this compact driver and need a more powerful model like the DCF887.

Question 6

the led light on my dcf787 stays on all the time, even after i take the battery out. how do i make it stop?

Accepted Answer

DIAGNOSIS The light circuit is stuck 'on'. This is a known capacitor issue on some runs of this model. A capacitor in the circuit holds a charge and keeps feeding the LED even with no battery. FIX It's a simple discharge trick. With the battery removed, pull and hold the trigger for a solid 30-60 seconds. You're draining the residual power from that capacitor. You might see the light dim and go out while you're doing this. Once it's out, you can release the trigger. When you put the battery back in, it should behave normally—light on only when the trigger is pressed. IF THAT DIDN'T WORK If the light stays stubbornly on with the battery *in* but the trigger not pressed, the trigger switch itself might be faulty or have debris causing a partial short. HEADS UP This isn't a sign the tool is broken, just a quirk. If the discharge trick works, the light might occasionally do it again in the future; just repeat the process. It doesn't affect driving performance.

Question 7

dewalt dcf787 impact driver is making a really loud grinding or rattling noise when i pull the trigger, sounds bad.

Accepted Answer

DIAGNOSIS Yeah, this one's common. That's usually the anvil—the part that holds the bit—or the hammer mechanism. A lack of grease or metal shavings in the gear case causes the grinding. FIX Remove the bit. Look inside the collet (the chuck). See if there's a bunch of black gritty dust or metal flakes. Blow it out thoroughly with compressed air (can of air works). The real fix often requires adding grease. You need to remove the rubber boot around the anvil to access the grease port. Peel it back, and you'll see a ring. Applying a small amount of impact-rated grease (like DeWalt's own) to the exposed ring and anvil can quiet it down significantly. IF THAT DIDN'T WORK If the noise is a high-pitched whine or squeal from the motor itself, not a grind, that's different. That could be a failing motor bearing, which isn't a user-serviceable part. HEADS UP Don't use WD-40 or general oil as a substitute for grease here. It'll attract more dust and make things worse. If the grinding is severe and the tool has lost impacting power, the hammer or anvil teeth might be stripped, which needs a repair center.

Question 8

my new dewalt 20v impact driver won't run at all, the battery's charged and it's just dead, what gives?

Accepted Answer

DIAGNOSIS This is almost always a battery connection issue, not a dead tool. The contacts on the driver or the battery can be too tight or have packing debris. FIX First, take the battery off. Look into the battery port on the driver. You'll see two flat, spring-loaded metal contacts at the top and two wider contact pads at the bottom. Press on the springy top contacts with your finger to make sure they're moving freely and not stuck. Then, look at the terminals on the battery itself. Give both the battery and the tool's contacts a quick wipe with a clean, dry cloth to remove any plastic film residue or dust. Re-seat the battery with a firm, solid push until it clicks. IF THAT DIDN'T WORK Try a different 20V MAX DeWalt battery if you have one. If it works, the problem is your original battery. If it still doesn't work with a known-good battery, the tool's internal trigger or board might have a factory defect. HEADS UP Don't try to bend or modify the contacts. If they're physically damaged or the tool is DOA, it's a warranty claim. The DCF787 has a 3-year limited warranty from the date of purchase.

DeWalt 20V Max Impact Driver DCF787C1

Other Power Tools