Choosing the right drill bit for Tapcon screws depends on the size and that really matters. The bit must be a bit smaller than the screw so that the threads grip the edges of the drilled hole. Usually you take a bit 1/16″ less than the screw
For 3/16″ Tapcon screws use a 5/32″ drill bit. Right choice for 1/4″ Tapcon screws is a 3/16″ bit. Packaging sometimes confuses: it says 1/4″ for those 1/4″ screws, but actually requires a 3/16″ bti.
Drill Bit Size and Hole Depth for Tapcon Screws
The chart suggests a 5/16″ bit for 3/8″ Tapcon concrete anchors. Always follow the manufacturer instructions about the drill bit size.
Hole depth also matters. For 3/16″ and 1/4″ diameter Tapcon screws drill the hole at least 1/4″ deeper than the depth of the screw. For 3/8″, 1/2″, 5/8″ and 3/4″ sizes the hole must be at least 1″ deeper.
Drill at least 1/2″ more than the screw length for standard sizes, that is a good rule.
Carbide-tipped Tapcon drill bits have more strict tolerances than ANSI standards. This means less breaks during work. 3/16″ Tapcon bits have more strict tolerances than average ANSI bits, which helps to keep precise size for maximum hold.
The best way to drill such holes is with a rotary hammer drill. Many hammer drills use only SDS bits, so if there is no adapter for a normal drill chuck, you will have to buy an SDS style drill bit. Even so for other materials like stucco or masonry it is possible to use a normal battery drill with small diameter Tapcon screws, because the holes are not hard.
There are small Tapcon screws for 5/32″ bits, but they are not very common. Bosch bits in 5 packs work for normal drills. The Bosch Blue Granite bits work well on concrete.
A shorter bit, for example 3-1/2″ long, is easier to keep straight than a 5″ Tapcon bit.
Embedment depth is another important thing. For 3/16″ and 1/4″ Tapcon screws the minimum is 1″ and maximum 1-3/4″. For 3/8″ Tapcon screws the range goes from 1-1/2″ to 2-1/4″.
Occasionally the carbide bit hits rebar, which damages the bit because of the wrong geometry. Then drill a new hole elsewhere. Clean the hole after drilling (a shopvac will help).
Hex head screws with a right driver best drive Tapcon screws.
