Picking the right drill for concrete anchors is one of those tasks that seems easy but often trips people up. Usually you use a drill of the same diameter as the anchor. That rule counts for wedge anchors, Tapking HD concrete screws, Mungo anchors, sleeve anchors, split-fast anchors, pin drive anchors and hammer drive anchors.
For metric Mungo anchors the drill diameter matches the anchor in millimeters
How to Choose the Right Drill Bit for Concrete Anchors
For instance, for a 1/2 inch concrete wedge anchor you need a 1/2 inch drill. Whatever the diameter of the stud is, that determines the hole size. For precise and strong drilling you should use carbide-tipped bits compliant with ANSI Standard B212.15.
Even so for a 1/2 inch concrete anchor you usually use a drill of 1/2 inch or 5/8 inch. The slightly bigger 5/8 inch bit helps with better alignment and simple instlalation. The minimum hole in the base for a 1/2 inch 2-3/4 inch wedge anchor zinc plated is 5/8 inch.
After drilling you clean the hole with a wire brush, vacuum, compressed air or a blow-out bulb.
For M8 anchor bolts the right drill diameter is 10 mm. That guarantees right fit and strength in concrete. With 6 mm anchors a 6 mm drill works perfectly.
A hammer drill is ideal for such work.
The hole depth is also important. You drill to a depth at least 1/2 inch or one anchor diameter more than the required depth. It is good to drill a bit more deeply than the anchor length.
Like this, if you ever need to remove the anchor, only the hole stays. The hole must always be clean and empty before you put in the anchor.
For different materials you use separate bits. For tile or glazed surfaces use a carbide-tipped masonry bit or diamond-tipped bit, drilling slowly with water to avoid cracks. For steel or metal take cobalt or HSS-coated high-speed steel bits with cutting oil.
Wood needs brad point, twist or spade bits according to the anchor pilot needs.
Blunt drills make too small holes, so change bits often. In solid concrete from C20 to C40 standard depths apply. In high-strength concrete C50 and more you may need a smaller interval.
For hollow blocks or bricks use sleeve anchors or chemical anchors with mesh sleeves.
One SDS plus bit lasts for 24 holes easily. For good installation of anchors with a 1/2 inch pilot hole, a hammer drill with a 1/2 inch concrete drill bit works well. Each Tapcon concrete screw has a minimum depth, and the hole must be drilled more deeply than the penetration in the base material.
Always check the package of the maker or the website for the right hole size if you have a doubt.
