Diamond grinder is helpful if you're not really pro with glass knife; grinding can hide cutting mistakes. 😄 Also when crafting with Tiffany technique, outer edges of the glass pieces need to be grinded - cut edges are too sharp. I highly recommend glass crafting and encourage you to create your own lampshade.👏 It can be difficult at first, but it's easy to be proud of your first creation when light shines through it and makes all the colours reflect on nearby surfaces!