If a belt walks to one side, stop the grinder before it runs off the wheels. The fastest way to narrow it down is to compare the suspect belt with a known-good belt on the same setup. One belt drifting points you toward that belt. Several belts drifting the same way point you toward the grinder or attachment.
Check the belt first
With the grinder off and disconnected, confirm you have the size the grinder calls for. Inspect the edges and splice. Set aside any belt with a torn edge, crease, or lifting joint. When you mount a belt, follow any directional markings and the grinder maker’s instructions for seating and tension.
Check what changed on the grinder
If the drift started after swapping a platen or contact wheel, check that the tooling arm is seated and secured. Look for debris or uneven wear on the wheels and check the setup for obvious misalignment. Use the manufacturer’s procedure for checking alignment and setting tracking. Follow its instructions for any powered test and keep hands clear of the moving belt and wheels.
Watch when it drifts
If the belt runs steady with no load and moves sideways only when the work touches it, pay attention to how the piece meets the belt. Side pressure or a catch at the belt edge can move it. Stop and check the belt position, work support, and technique before resuming. If multiple sound belts still drift after the manufacturer’s checks, have the machine inspected.
Once the belt runs steadily, use the 2x72 grit progression guide to get back to the right grit for the job.