>It will crack if it is hit it VERY hard
True, it's not indestructable ;P
It will also do strange things if it gets caught in the tooth of a table saw....
lexan/acrylic - I probably caused more confusion that help, point was , the stuff at home depot will be acrylic unless you look for the other stuff, it is cheaper ....
1930 - I may have some cutoff's floating around, but it will be a few days before I can go look.
meanwhile, how are you going to mount them? If you have no frame, you can drill the thicker stuff....
Or you could just buy some safety glasses ;P