just got this saw and the blade keeps falling out while i'm cutting, i've pushed it in until it clicks but it's still loose

Diagnosis

The issue with the Makita XRJ05Z is typically not a failure of the locking mechanism itself, but a failure of the blade to seat fully within the keyed chuck. Because this model uses a tool-less, quick-change system, it relies on a precise mechanical interface between the blade's shank and the internal locking pins. If the blade is not pushed in past the secondary "click" point, the locking collar may feel engaged, but it is only gripping the outer edge of the shank rather than locking the keyed notch. This often happens because sawdust, metal filings, or factory lubricant buildup has accumulated inside the chuck bore, preventing the blade from reaching the full depth of the socket. Furthermore, if you are using a non-standard or off-brand blade, the shank dimensions may vary by fractions of a millimeter, which is enough to prevent the internal spring-loaded detent from fully capturing the blade, leading to "blade creep" where the vibration of the cut gradually pushes the blade out of the tool.

How to Fix It

To properly secure the blade and ensure it does not eject during operation, follow this precise sequence:

1. Remove the battery from the XRJ05Z to ensure total safety before manipulating the chuck.
2. Pull the locking collar (the sliding sleeve) completely back toward the handle and hold it in the open position.
3. Insert the blade shank into the chuck. Do not just push until you feel a slight resistance; push firmly until the blade hits the back of the housing.
4. While keeping the collar pulled back, give the blade a slight wiggle to ensure it is centered and not hitting any internal debris.
5. Release the locking collar abruptly. You should feel and hear a distinct, metallic "snap" as the collar seats.
6. Perform a "Tug Test": Grasp the blade firmly and pull it straight out of the tool with moderate force. If it moves even a millimeter, the locking collar has not fully engaged the key.
7. If the blade still feels loose, repeat the process but use a small amount of dry PTFE lubricant on the blade shank to help it slide past any internal friction points.

If That Didn't Work

• Deep Clean the Bore: Use a thin wire brush or a dental pick to scrape out the interior of the chuck. Metal shavings from previous cuts often wedge themselves at the very bottom of the socket, creating a physical barrier that prevents the blade from seating deep enough for the lock to engage.
• Verify Blade Compatibility: Check the shank of your blade. The XRJ05Z requires standard 1/2" universal shanks. If you are using a blade with an oversized or slightly tapered shank, it will not lock. Try a genuine Makita blade or a high-quality Diablo blade to see if the issue is specific to the blade brand.
• Inspect the Locking Collar Spring: With the blade removed, slide the collar back and forth. If the movement feels "mushy" or it doesn't snap forward with force, the internal return spring may be fatigued or obstructed. Use compressed air to blow out the gap between the collar and the tool body to clear any packed sawdust.
• Check for Deformed Shank: Inspect the blade shank for any burrs or bends. Even a slight deformation in the metal of the blade can prevent the keyed locking system from aligning perfectly, causing the blade to vibrate loose during high-RPM cutting.

Heads Up

• Never use a hammer or pliers to force the locking collar closed; this will deform the precision-machined housing and permanently ruin the tool-less change system.
• Always remove the battery before changing blades to prevent accidental trigger pulls, which can cause the blade to jump and damage the chuck.
• Avoid using oil-based lubricants inside the chuck, as these attract sawdust and create a thick paste that will eventually jam the locking mechanism.
• Regularly blow out the chuck area with compressed air every 5-10 blade changes to maintain the integrity of the quick-release system.