This will give you the minimum length of screw that can be used. The length of the screw used for any specific application is determined by adding the minimum embedment of 1” the thickness of the material being fastened. The length of screw used is based on the thickness of the material being fastened. The diameter of the screw used for a specific application is determined by the holding values required and the diameter of the hole in the item being attached. Each diameter comes in lengths from 1-1/4” to 6”, but not all lengths are available in both diameters. They come in two diameters of 3/16” or 1/4”, with each diameter available in a number of different lengths. The first number represents the diameter of the screw and the second number equals its length. The dimensions of all masonry screws are described with two numbers. Using a wire brush, compressed air or vacuum in combination is usually sufficient to clean out the hole before inserting the screw.ĭimensions for Self-Tapping Masonry Screws Once the hole is drilled, it must be cleaned of all dust and debris or holding values may be affected. This will ensure that the hole is the proper shape and tolerance in order to allow the screw to obtain minimum holding values. The hole in the masonry must be drilled using anĪNSI standard carbide tipped bit used in a hammer drill that is set in the hammer and rotation mode. Any variance in hole size will affect the holding values and may make the holding values not existent. ANSI standards ensure proper hole dimension tolerance requirements. The hole must be drilled using a carbide drill bit that meets ANSI standards. The guidelines for masonry screw anchors are as follows: the 3/16” diameter requires the hole diameter to be equal to 5/32” and the 1/4” diameter requires a 3/16” hole. The hole diameter is critical and must be drilled in accordance with the manufacturer’s instructions. Therefore, the hole drilled in the masonry must be slightly deeper than the screw will penetrate to allow space for the dust that is created during the taping process to fall into and out of the way. The threads are designed to allow the dust to be removed and to prevent interference with the screw installation. As the threads are cutting into the masonry, dust is created. The lead thread will dull and hit a point where it will no longer be able to cut threads and will stop screw penetration. The abrasiveness of the masonry will determine the exact depth that any specific screw can tap. When tapping threads into masonry, the lead thread does all of the cutting of the masonry material and isĭesigned to cut threads up to 1-3/4” in depth. A self-tapping screw does not drill a hole and tap threads, which would be. A self-tapping screw is a screw that taps its own threads when screwed into a hole.
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