20Pcs Diamond Grinding Bits, 10mm Cylinder Head, 3mm Shank, 45mm Long Diamond Coated Burr Mounted Point

Cuts and shaves rocks like a champ. I use water to make it last but they wear down fast.

I'm creating the mosaic in the first picture, it's about 33" diameter. I needed something to allow me to get into the inner bends of the 'S' (for South) shown in the second picture. These absolutely worked perfectly. I used them in a Dremel with one of the bases to keep the bit at the right height off the tile, adjusted the depth...shallow cut first, then deeper, then full cut. I kept the cut wet with a cloth soaked in water. Grind, grind, grind, wet, grind, grind, grind, wet...you get the idea. I used two of the 20 bits supplied to grind the inside of the 'S' and to smooth out the outside bends. I probably could have kept using the first one, but changed out just in case. I've found that diamond bits work a lot better if you keep even the slightest drops of water on the working piece. These work great, and are at a great price.

Grinding surface peeled off within one minute of grinding with two different grinding bits . Unless, and cheaply made

Use these to move or enlarge holes in hardened steel. They do wear out after a dozen or so uses. but at 50c each that is not really an issue.

enlarging holes in lamps to run lights thru

Works great even grinder

They work well but they just don't last long

The grinding power was not there. Maybe this is more for polish work . At high speed "high rpm" the head wobbles and shaft bent over.