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:
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: