How to Replace the Lock Nut on a Makita Grinder

The lock nut is one of two flanges that secure the grinding wheels to your grinder. It has a 5/8-inch threaded hole, so it can be secured to the grinder's spindle. One side has a 7/8-inch hub for attaching standard grinding wheels to the grinder. The other side is flat, and can be used to secure thin cutting discs or diamond wheels. The hub on the lock nut can wear over time, causing the grinding wheel to wobble.

Let's get started.

REMOVING THE LOCK NUT   1. Remove the lock nut.

a. Depress the spindle-lock button on the top of the gear housing.

b. Rotate the grinding wheel until the spindle-lock engages.

c. Use the spanner wrench to loosen and remove the lock nut from the spindle.

INSTALLING THE NEW LOCK NUT

  2. Install the lock nut.

a. The lock nut is reversible: If you are using standard-sized grinding wheels, the raised portion of the center hub (on the lock nut) should face the grinding wheel. If you are using cut-off discs, the flat side of the nut should face the discs.

b. Thread the new lock nut onto the spindle (with the appropriate side of the nut facing the grinding wheel or cut-off disc).

c. Depress the spindle-lock button on the top of the gear housing.

d. Use the spanner wrench to secure the lock nut to the spindle.