Toggle Bolt Specifications

Written by chuck ayers
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Toggle Bolt Specifications
A bolt without the spring-loaded flange that screws onto the bolt and opens like butterfly wings on the opposite side of masonry or concrete to support heavy hanging objects. (barb bolt image by Maksim Shebeko from

Toggle bolts, also known as flange bolts, consists of a carbon steel alloy machine screw (bolt), with an independent spring-loaded wing, or flange, that spreads when the unit is inserted through a drilled hole in an applicable surface and the screw is tightened. Toggle bolts are used to evenly distribute load capacities in a hollow wall, block or other hollow material. Standard sizes for the machine screw in a toggle bolt range from 1/8 inch to 1/2 inch in diameter and 2 inches to 6 inches long. The diameter of the closed toggle varies accordingly, as does its open wing span and its load-bearing characteristics. The head of a toggle bolt can be a flat head screw, slotted hexagonal, Phillips head or round mushroom.

Tensile Strength vs. Shear Strength

When using toggle bolts, two types of strength must be considered. One is the tensile strength, which is the strength of the bolt itself. The other is shear strength, which refers to the strength of the material in which the bolt is anchored. If the load exceeds the tensile strength, the bolt will snap. If it exceeds the sheer strength, the load will pull away from the material into which it is anchored.

Load Maximum Load Specifications for Toggle Bolts in Wallboard

Starting with the smallest diameter toggle bolt (1/8 inch) and thinnest acceptable wallboard (3/8 inch), the bolt can be expected to support 115 tension pounds and 120 shear pounds. At the high end of the spectrum, bolts with a 1/2 inch diameter in 5/8 inch wallboard, loads top out at 188 Kilogram of tension strength and 400 shear pounds. These are maximum allowable loads. It is advisable for use in plasterboard to err on the side of caution by either over-sizing the toggle bolt or reducing the load weight.

Maximum Load Specifications for Hollow Concrete Masonry

The maximum load limits for hollow concrete masonry are based on the assumption that the breeze block masonry is a minimum of 6 inches wide. For a 1/8 inch diameter toggle bolt, the maximum tension is 88.5 Kilogram and maximum shear weight is 86.2 Kilogram. If you're hanging something very heavy in masonry, the top end weight loads for 1/2 inch diameter bolts are 526 Kilogram of tension weight and 363 Kilogram of shear weight.

Toggle Bolt Drilling Specifications

Because the flange is wider than the bolt, the hole to fit the toggle flange through masonry must be wider than the diameter of the bolt. Wallboard is not as stiff and unrelenting as concrete so the diameter of the drill bit can be as little as 1/16 to 1/8 inch larger than the diameter of the bolt. In masonry, the drill bit size must be large enough to accommodate the flange to pass through the drill hole to the other side. As a rough rule of thumb, the drill bit size should be twice the size of the anchor bolt diameter plus approximately 1/8 to 1/4 inch, depending on the size of the flange.

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