Review on Dewalt DW5440 16 18 Inch Carbide by Ralph Banks

I bought this to drill some holes in granite rock. The drill has performed well drilling approximately 9 holes along the full length of the drill. Then I noticed a rebound on the last hole. I pulled the chisel out and then found that the carbide head had been lost in the rock and the chisel was getting very hot. Not sure if I broke it or got a bad one. I ordered another one along with a Bosch counterpart so I can do a comparison. The only thing that I think could have caused it to fail is that there was some water on some spots on the rock where I was drilling. This could cause the hot metal to harden, leading to premature failure. I'm not sure. I have other carbide bits that work fine so I'm hoping I just got a bad one. To update. The Dewalt bit seems to cut faster and remove dust better than the Bosch bit, but I killed another one. I think it's possible that the stone has different densities causing the bit to fail prematurely. Should work well in concrete.