the chuck on my craftsman cmcd710 keeps coming loose while i'm drilling. how do i tighten it properly?

Diagnosis

The slipping chuck on the Craftsman V20 CMCD710 is typically caused by a failure in the mechanical grip of the three-jaw system, often resulting from "over-clamping" or a lack of sufficient torque applied to the outer sleeve. In many cases, users rely on the motor's rotation to "snap" the bit into place, but this creates a loose fit because the internal collet hasn't been fully seated against the bit's shank. This allows the bit to rotate independently of the chuck's internal spindle, causing the bit to spin out or the entire chuck assembly to loosen during high-torque applications. Another common cause is the accumulation of metal shavings, drywall dust, or sawdust inside the chuck jaws. These contaminants create a microscopic layer of lubrication or debris that prevents the jaws from biting into the metal of the drill bit. You can confirm this by removing the bit and inspecting the jaws; if you see a grey or white powdery residue, the friction coefficient is reduced, and the bit will slip regardless of how hard you tighten the sleeve. Additionally, if you are using a hex-shank bit in a non-keyed chuck without ensuring the bit is centered, the off-center rotation creates a centrifugal force that actively unscrews the chuck as you drill.

How to Fix It

Follow these steps to ensure a secure, slip-free grip on your drill bits:

1. Remove the 20V battery pack from the base of the tool to prevent accidental trigger pulls while your fingers are in the chuck.
2. Open the chuck jaws fully by rotating the sleeve counter-clockwise. Use a can of compressed air or a stiff nylon brush to clean out any debris from the three internal jaw recesses.
3. Insert the drill bit. Ensure the bit is pushed all the way to the back of the chuck. If using a round-shank bit, ensure it is perfectly centered; if using a hex-shank, ensure it is seated firmly against the rear wall.
4. Tighten the chuck sleeve clockwise by hand. Rotate it until you feel the jaws make initial contact with the bit.
5. Apply a "firm-grip" tighten. While the CMCD710 is a keyless chuck, you must apply significant manual pressure. Grip the sleeve firmly and rotate it an additional 1/4 to 1/2 turn past the point of initial resistance. Do not use the trigger to tighten the bit, as this often leaves the jaw tension inconsistent.
6. Set the gear selector on top of the drill to Position 1 (Low Speed/High Torque) for larger diameter bits or harder materials. This reduces the RPM-induced vibration that can cause the chuck to loosen.
7. Reinsert the battery and perform a low-speed test rotation before applying full pressure to the workpiece.

If That Didn't Work

• Check for Jaw Wear: Inspect the internal teeth of the chuck jaws. If the metal is smoothed down or "polished," the chuck has lost its grip capacity. This requires a replacement of the chuck assembly, as the internal threads cannot be resurfaced.
• Switch Bit Types: If you are using round-shank bits and they continue to slip, switch to impact-rated hex-shank bits. The flat sides of a hex bit provide significantly more surface area for the jaws to grab, eliminating the rotational slip common in the CMCD710's keyless system.
• Lubricate the Collet: Apply a single drop of light machine oil (like 3-in-1 oil) to the outer sleeve and rotate it open and closed several times. This ensures the outer sleeve is transmitting all your manual torque to the internal jaws rather than binding due to friction.
• Verify Bit Length: Ensure you aren't using an excessively long bit that creates a "lever effect," which can put uneven lateral pressure on the chuck and force the jaws to open. Use the shortest bit possible for the task.

Heads Up

• Avoid using pliers to over-tighten the keyless chuck; doing so can strip the internal plastic or soft-metal threads, rendering the tool useless.
• Always clear debris from the chuck before inserting a new bit to prevent the "lubrication effect" of sawdust.
• When drilling into hardwood or metal, periodically stop to check that the chuck hasn't vibrated loose, as high-frequency vibrations can naturally unscrew keyless sleeves.
• Store your V20 tools in a dry environment to prevent oxidation (rust) inside the chuck jaws, which can lead to "seizing" or inconsistent gripping.