SCB0312D 3.5-Inch Diamond Core Drill Bit for Granite, Concrete, Tile - Wet/Dry Use - Heavy Duty Hole Saw for Masonry, Stone Cutting - Perfect for Construction, Renovation & DIY Projects

These work just fine through an un-grouted cinder block wall. It does a nice clean job. But be aware that it's easy to break a wrist with one of these things if you're not careful. To start, I sincerely encourage you to use a ROUND core bit adapter (aka 'arbor'), like the Toolocity AD1112. The round shank will permit the drill's chuck to slip if you bind-up. Otherwise, it's your wrist that'll break. If you use a beveled bit-adapter, like the ToolCity 0038, that chuck will NEVER slip (actually, there's so much force applied that the damn arbor will bend like a pretzel) Next, consider buying a concrete arbor with a pilot drill. That's money well spent cause you'll be far less likely to bind-up. If you don't use a arbor with a pilot, you'll have to make a jig out of plywood to hold the core (otherwise it just skips around and you can't start the hole). If you're gonna drill, say, a 3.5" hole into cinder-block, first cut a round hole in a 10"x10" square of plywood using a sawzall bit. Then drill masonry-screw holes in each corner and attach it to the wall. That'll keep the core bit from moving around. When you drill, drill as slowly as your patience permits so if it binds it'll be manageable. Whatever you do... always position your wrist so you can let go WHEN it binds (and believe me, it will bind!).