Z Axis skips a step ONLY on last step, cutting .25 holes

When I cut .25 (.252)D holes with a .25 flat fluted bit, on the very last step/pass it seems to skip a step and renders the rest of the cuts on the project not deep enough.

I’m pretty sure the belt is taut as I do not think it’s the belt skipping a tooth. If you were to jog the Z-axis upward past it’s limit, the motor seems to skip (or ratchet), not the belt. This is what I think is happening at the bottom of these holes. I’ve heard what it sounds like when the belt skips, this isn’t that sound.

I just played with the machine as I’m typing this, I held the z plate while jogging the machine downward and the motor skipped. Is it possible the motor isn’t strong enough? I can’t see that being an issue because I feel like this cutter and router should cut through plywood like butter.

I’m at a loss.

@Marshall

Z Belt tension could a factor on your Shapeoko.

However, the location of the Router in the clamp could be the issue.

Try jogging the machine to the bottom of your cut (max depth) and see if the router position and tool hangout is giving you the reach you need to finish the job.

Had to use a small prybar on mine (careful to not bend the shaft)

http://www.shapeoko.com/wiki/index.php/Shapeoko_3#Belt