In the 1830s, square-headed bolts were superseded by the hex head. The widespread use of hex head nuts and bolts came about due to innovation in engineering and metallurgy. Hex-head nuts and bolts and the tools to use them require close tolerances, whilst square heads required less accurate tolerances.

Square-headed bolts and screws were commonly used in early applications. When machinists used cast iron and cruder forms of steel, square bolt heads were easier to make with the tools, metals, and techniques of the time. As machinery became smaller and more compact, however, the hexhead bolt evolved to meet the need for more compact bolt heads.

To complement our range of fixtures and fittings, we have sourced a number of vintage-style industrial square-head lag bolts in a black oxide finish. They are available in a variety of sizes and lengths to suit various applications such as furniture construction, woodworking projects, lighting design, and any vintage industrial project. These lag bolts will create a more authentic appearance in your work.

We strongly recommend the use of a corresponding sized rub/shim washer in conjunction with and square-headed lag bolt to prevent surface scrubbing.

For those of us who struggle with imperial measurements, we have included metric equivalents next to the sizes, usually in brackets [].

Make installation of your lag bolts, pyramid head door screws, and square head machine bolts easier and safer with our 8-point sockets.

https://littleanvil.com/nuts-bolts-screws/8-point-socket

Currently, we carry a limited range of sizes and a small amount of stock. We will continue to increase our range and stock levels over time. Contact us if you require a specific size, not in the list, or a larger quantity. Please allow a 2-3 week lead time for delivery of non-stock items.