Techniglass1 Inch GelBit Glass Grinder Bit

I was so disappointed in this grinder bit. I have been doing stained glass for fifty years and was happy to see a possibly better grinder bit. I bought the fine and medium grit. These bits chattered which resulted in a rough and uneven surface. I tried everything I could think of and nothing stopped the chatter. I only wish I had tried them before the product return window had closed. Oh, well, live and learn.