This bit worked really well once it gets started correctly and is kept wet with a constant stream of water, but that’s a given when drilling stone, block, brick, or other forms of masonry. I drilled though red brick and the concrete block just behind it in about 10 minutes. But the pilot bit is terrible. The way that the arbor at the top of the drill tube is machined causes the pilot bit to be very lopsided. I fixed this by two different methods. The first, I put some tough wire around the pilot bit at the edge of the tube (see the picture) and I centered the pilot bit by using three pieces of wire one attached to every other tooth on the tube, I tightened the wire with lineman pliers. That worked ok as the wire would break away once the drill tube started into the block but before the pilot bit would go off to one side. But then for another job I improved on my design and drilled a three inch hole with wood hole drill into a piece of one inch wood. I sanded down the edges a bit so it would fit the tube loosely. I then placed this cutout, with a little black tape wrapped around it to make it snug, into the very front of the tube (see the other picture). This worked extremely well, as the drill tube went into the block, the wood cutout traveled up the drill tube. But once I got about three quarters or an inch into the tube I removed the wood cutout and the pilot bit since neither were necessary any longer. The bit sailed through the brick and concrete block. Perhaps the manufacturer could make a design change and have an insert that would keep the pilot bit centered but also ride up the tube as you bore the hole. All in all, this a good product for the money. Just remember to have someone help you and keep spraying water right onto the front of the bit and into the hole you are drilling. No matter what, never drill masonry dry, your bits will last much longer if you keep them cool and wet.
JC 
