Why Is My Router Bit Height Increasing After Cuts?

There are a couple of things to consider. First, it’s possible the bit isn’t as tight as you think, or maybe some debris is affecting the grip. Also, that digital gauge you’re using isn’t super high-end, so accuracy can be a bit off. A few thousandths can be difficult to measure accurately, and it sounds like your gauge's tolerances might not be precise enough for what you need. It could also just be a normal tolerance issue related to your tools. Just keep an eye on it, especially if the creep is noticeable visually.

Make sure when you're raising the bit that you're going above the radius where the shank meets the cutter head. Otherwise, the collet might not hold it tight all the way down. It sounds simple, but this can make a big difference. Best of luck with your setup!

Also, consider that a couple of thousandths can stem from play in the router's bearings. When you tighten the bit in the collet, make sure it’s all the way down. Sometimes the bearings need to settle when the router is running. Next time you measure, try tightening the bit, then running the router without cutting, and check the height again afterwards.

It sounds like the lift might be creeping up due to vibration rather than the bit itself moving in the collet. You might want to check if everything is tightened properly, especially the tension on the lift itself. Sometimes if the setup isn't secure, vibration can cause height changes during use. Doing a recalibration of the thread tension should help—let us know what you find out!