Diameters of Blue Screws
The standard blue screw comes in two diameters of 3/16” and 1/4” while large diameter Tapcons comes in of 3/8”, 1/2”, 5/8” and 3/4”. The diameter of the blue screw to use for any application is determined by the holding values required, by the diameter of the hole in the fixture or if an engineer has specified it. The blue screw - Tapcons or duplicates - are designed for use in solid concrete, brick or block (CMU) base materials.
Lengths of Blue Screw
The blue screws come in different lengths ranging from 1-1/4” to 6”. The length of the blue screw to use for any application depends on the thickness of the material being fastened and the embedment depth. To determine the minimum length of blue screws to use, add the thickness of the material to the minimum embedment depth of 1”. To calculate the longest blue screw’s length, add the thickness of the material being fastened to the maximum embedment of 1-3/4”. The hex head blue screw’s length is measured from underneath the head, while the flat-headed blue screw is measured as an overall length including the head.
- Minimum Embedment - the minimum embedment depth for the 3/16” and 1/4” blue screw is 1”. Both these diameters must be installed into the base material at least 1” for the blue concrete screw to obtain minimum holding values.
- Maximum Embedment - Both the 3/16” and the 1/4” maximum embedment are 1-3/4”. Trying to embed the blue screw deeper than 1-3/4” may cause problems, such as the blue screw becoming stuck in the hole or, if too much torque is applied, having the blue screw shear off about 1/4” to 3/8” from the head. The maximum embedment is also affected by the hardness and abrasiveness of the base material. The harder and the more abrasive the base material is then the shallower the maximum embedment might be.
Diameter of Hole
Each diameter of blue screw requires a specific diameter hole be drilled into the base material. Holes size is critical for the blue screw to have holding values and must be drilled using a hammer drill with a carbide-tipped drill bit that meets ANSI standards.
|Diameter of Bit
Depth of Hole
The hole must be drilled to a depth of 1/4” deeper than the blue screw will penetrate the base material. This leaves space for any dust to fall into that is created during the installation process. As the blue screw is inserted into the hole, the lead threads tap threads into the base material. This tapping process creates dust and must have a place to go or it will interfere with the proper installation.
Size of Head
The size of the head determines the size of the socket that must be used to install the blue screw. Both diameters of blue screw have a different head size and socket size. The flat head Phillips tapcon requires a #2-bit tip for the 3/16” diameter and a #3-bit tip for the 1/4”. The 3/16” diameter blue screw needs a 1/4” nut driver or socket, and the 1/4” blue screw uses a 5/16” nut driver or socket
Installing Blue Screws - 3/16” and 1/4” Diameter
- Use the hammer drill and 5/32” carbide tipped drill for the 3/16” diameter blue screw and a 3/16” carbide tipped drill bit for the 1/4” tapcon. The bit must meet ANSI standards.
- Drill hole in the base material a minimum of 1/4” deeper than the blue screw will penetrate the base material. Clean out the hole of all dust and debris created during the drilling process.
- Insert the blue screw through the fixture and into the hole in the base material.
- Using the correct driver, turn the tapcon blue screw clockwise until the head of the tapcon is snug against the material being fastened.