JINGLING 13mm 1/2" Diamond Hole Saw Drill Bit Coated Masonry Tools for Rocks Stone Glass

The JINGLING Tile Hole Saw Diamond Drill Bits are a set of 5pcs that come in pack and are made in China. The bits are designed to slowly sand through surfaces like stone, glass, concrete, and ceramics in a slow and patient process. They work great on some surfaces but can be blunt when used on stones. Although they look like they have a round shaft, there are three flats ground into them for very positive attachment to a drill chuck. Users recommend starting the drill at a relatively low speed and at an angle to begin and occasionally dip it in water to cool it off. There is no need to drill a smaller pilot hole, just start the drill and put it at an angle to start the hole, then tip it upright and press it through. One bit used to cut 2 holes right through bathroom ceramic tile in 30 seconds each hole. The bits worked well and cut through 3/4” granite and a granite countertop, most users managed to drill about 10 pcs with one hole saw. The item is well worth the price.