Which lens to use

[Stroonzo (Jeff)]

Problems with Baltic Birch Plywood

Here is a good write up about the tolerances on focal length: https://buildyourcnc.com/tutorials/tutorial-CO2-Laser-Optics-Lens-Selection-Focal-length And another good read here:

As seen on https://lasergods.com/laser-lenses-optics-and-focus/