the fine depth adjustment knob spins but the bit doesn't move up or down. adjustment is useless.

Diagnosis

The failure of the fine-depth adjustment knob on the DeWalt DCW600B is typically caused by a disconnection between the fine-tuning worm gear and the main plunge mechanism. This happens when the coarse adjustment locking lever is not fully seated or when the internal drive pin has slipped out of its mating slot due to excessive vibration or an accidental impact to the side of the tool. When the knob spins without resistance, it indicates that the gear is rotating freely without engaging the threaded collar that lifts or lowers the motor assembly. You can confirm this by observing the plunge assembly while turning the knob. If the knob rotates smoothly with zero tactile feedback and the motor housing remains static, the mechanical link is broken. In some cases, sawdust and resin build-up within the adjustment column create enough friction to prevent the gear from seating properly, causing the mechanism to "jump" its track during a depth change. This is particularly common in the XR series when used for long periods in high-dust environments without clearing the plunge rails.

How to Fix It

To re-engage the fine-adjustment mechanism and restore precision depth control, follow these exact steps:

1. Disconnect the battery from the DCW600B for safety to prevent accidental motor activation during the reset.
2. Locate the coarse depth lock lever on the side of the plunge assembly. Fully release this lever, pushing it completely into the "open" position.
3. Hold the router motor housing firmly and manually move it up and down the column using the coarse adjustment to ensure the assembly is not jammed.
4. While the coarse lock is open, rotate the fine-adjustment knob counter-clockwise. Continue rotating it past the point where you normally stop; you are looking for a "click" or a sudden increase in resistance.
5. Once you feel the gear engage, rotate the knob clockwise slowly. You should see the motor assembly move in minute increments (approximately 0.005 inches per rotation).
6. Firmly snap the coarse depth lock lever back into the locked position. This clamps the main collar and forces the fine-adjustment gear into a tighter, more secure interface.
7. Test the movement by rotating the knob both ways. The motor should now glide smoothly without the knob slipping.

If That Didn't Work

• Clear Internal Debris: Use a high-pressure air compressor to blow out the plunge column and the area surrounding the fine-adjustment gear. If sawdust has packed into the worm gear teeth, the pin cannot seat deeply enough to engage. After cleaning, repeat the "Fix" steps above.
• Inspect for Sheared Drive Pin: If the knob continues to spin with zero resistance even after resetting the lock, the internal drive pin may have sheared. You will need to remove the fine-adjustment knob by unscrewing the center cap. Inspect the pin for any signs of metal fatigue or breakage. If the pin is snapped, the entire fine-adjustment assembly (Part No. DCW600-FineAdj) must be replaced.
• Lubricate the Plunge Rails: Apply a small amount of dry PTFE lubricant to the main plunge columns. If the rails are too sticky, the motor housing requires more force to move than the fine-adjustment gear can provide, causing the gear to slip or "skip" teeth.
• Check for Bent Column: Inspect the main aluminum plunge column for any slight bends or nicks. A dent in the column can create a "dead spot" where the fine adjustment will fail to engage because the motor housing is physically wedged against the rail.

Heads Up

• Never force the fine-adjustment knob if you feel significant resistance; this can strip the plastic threads or shear the drive pin, turning a simple reset into a costly part replacement.
• Always engage the coarse lock firmly before using the fine adjustment. The fine-tune knob is designed to work against the tension of the coarse lock, not as a primary lifting mechanism.
• Clean the plunge rails with a lint-free cloth and isopropyl alcohol every 10-15 uses to prevent resin buildup from interfering with the precision gears.
• Avoid transporting the router with the plunge assembly fully extended and unlocked, as vibrations can cause the fine-adjustment gear to shift out of alignment.