The size of the bit is determined by the size of the Tapcon® being installed. There are two dimensions that need to be determined: the diameter of the bit required and the length of the bit. These two dimensions must match the size of the tapcon being installed in order for the tapcon to achieve the holding value requirements.
The required bit for the tapcon screw is slightly smaller than the designated diameter of the tapcon. All bits used for the installation of tapcon screws must meet ANSI B212.15-1994 standards, have a carbide tip and be used in a hammer drill that is set in the hammer and rotation mode. The bit can be a straight shank that fits into the Jacobs style chuck, i.e. a chuck that requires a chuck key, an SDS style and, for the large diameter tapcon, the Spline and SDS Max can be used.
The diameter of the bit chosen is determined by the diameter of the tapcon being installed. The 3/16” tapcon uses a 5/32” bit, the 1/4” tapcon needs a 3/16” diameter bit, the 3/8” tapcon requires a 5/16”, the 1/2” tapcon requires a 7/16” bit, a 5/8”tapcon needs a 1/2” bit and the 3/4” tapcon requires the use of a 5/8” carbide tipped bit. Hole tolerance is critical and the use of the proper size bit is important to achieve the proper size and shape hole that is required for the tapcon concrete screw to achieve its minimum holding values.
The length of the bit that is chosen is critical. That is due to the differences in the depth of the hole in the base material, which is determined for each length and specific application of tapcon used in order to meet minimum embedment depths. Each diameter of tapcon concrete screw has a minimum embedment depth that it must be installed for the tapcon screw to meet minimum embedment requirements. The minimum embedment depth for each diameter of tapcon is as follows:
The hole must also be drilled to a depth exceeding the depth of penetration of the tapcon screw in the base material. This extra depth to the hole allows space for any dust that is created during the installation process to fall into and out of the way to insure proper installation. For the 3/16” and 1/4” diameter tapcon the hole must be drilled a minimum of 1/4” deeper than the tapcon screw will penetrate and for the 3/8”, 1/2”, 5/8” and 3/4” the hole must be a minimum of 1” deeper than the tapcon will penetrate. There are two lengths when describing a bit used for installing a tapcon screw, the overall length of the bit and the usable length of the bit. When using a bit the overall length is the length of the bit measured from end to end, the usable length is the amount of the bit that can be used after the bit is chucked into the hammer drill. The following charts show the diameter and length of the tapcon screw and the diameter and overall length of the carbide bit for the straight shank, sds, sds max and spline bit.
Please remember with all fastening jobs to keep safety in mind. Always follow safety instructions on all tools, and refer to manufacturer's installation instructions when available and always remember to wear safety goggles!
Article written by: Bob Carlisle, President Concrete Fastening Systems, Inc