No.  If used correctly, you will not break or scratch the glass or damage the black frit band. 

We recommend using cutting lubricant (baby shampoo in water is okay) and attaching the soft Velcro adhesive dots to the back of the blades to protect the glass. 

Glass moldings and encapsulation can be protected from damage by using reverse blades to steer away from the glass and encapsulation. 

Controller arms are used to control blade depth, eliminating damage to top moldings and paint.  The controller cap is plastic and will not scratch the glass.