Dremel 570 1/8 inch Carbide Grout Removal Bit

Hello I am removing the ground from the floor of my Roman shower The first blade 570 just cut right threw the grout and finally the tip caught on fire and I knew it was finished The second and third bit were done cutting after 20 min. I own two dremels. One pro with cord and one cordless. I like how the adjustable attachment guides the bit I do believe what others have said. At 15 a bit head this seams as if will be costly Disappointing

I should have read the reviews before shelling out for a Dremel 3000 plus the expense for a special grout kit. The bit that came in the grout kit is the same as noted here. Using it on the recommended speed it successfully removed grout for about 3 linear feet before the bit went dull. Unfortunately I still have 4 more feet to go. :( (sad face)