u/GunningBedford58

Over the past few weeks, I’ve cut and measured dozens of test boards trying to answer one simple question: How accurate is my CNC router, really?

The results were not what I expected, and they changed how I think about accuracy.

Absolute numbers matter less than consistency

I used to obsess over hitting exactly 1.000". But what ended up being more useful was seeing how consistent the machine was. If one side of a pocket is 0.998" and the other is 1.002", you’re good.

Especially in wood, consistency matters more than chasing metal-shop tolerances.

Diagonals tell the truth about squareness

A pocket can measure “correct” in X and Y and still not be square. Measuring diagonals revealed issues I would have completely missed if I only checked width and height.

Small errors get bigger when you scale up

A tiny deviation on a 1" pocket becomes very noticeable on an 8" feature. Measuring larger areas made patterns jump out that were invisible on smaller tests.

None of this required anything fancy — just digital calipers and a bit of patience. I was not even trying to diagnose machine problems at first; I just wanted to understand how it behaved. But doing this made it a lot easier to talk to support and provide them useful information.

Curious how others here check their machine’s wood accuracy —what do you measure? Are you aiming for exact numbers, or looking for consistency and patterns in your cuts?

When is a round pocket round enough?

I have been thinking a lot about CNC wood router accuracy lately — not the theoretical kind, but the real-world “what does my machine actually do when I hit Start?” kind.