All thread is produced in one of two ways in our shop. For common grades and sizes, we start from pre-threaded rods. Everything else is made from round bar. Watch both processes in our All Thread Rod video.
All thread rod is one of the most common fasteners used in the construction industry.
Most common grades of all thread rod are mass-produced by feeding steel round bar through a cylindrical die roll-threader. These rods are commonly produced, bought, and sold in ten foot and 12 foot lengths, where they could be cut to length on the jobsite. However, most all thread rod supplied in the industry is cut to size in a manufacturing facility.
The process begins with a 12 foot piece of all thread rod, which is cut to the desired length on a bandsaw. Once the rods have been cut, they undergo a chamfering process. Chamfering machines act like large pencil sharpeners which bevel the ends of the rods to ensure easy installation of the nuts.
Other common end types for the all thread rods include angle cut and chisel point. These two end types are used for adhesive anchors where the special ends break epoxy capsules and facilitate proper mixture of the adhesive in the concrete.
If the rods are being used in outdoor applications, they will likely need to have a galvanized coating to protect against corrosion. It is important that the all thread rod be galvanized in a system that is specifically designed for threaded fasteners. The rods undergo caustic soda, sulfuric acid, and flux solution baths to prepare the steel to bond with the molten zinc. When preparation is complete the rods are submerged in a tank of 840 degree molten zinc for a designated amount of time to allow the zinc to bond with the steel. Once removed from the molten zinc the rods are spun in a high-speed centrifuge, to remove excess zinc from the threads, and then cooled in a water bath for immediate handling.
The last step in the manufacturing process is stamping the material with the required grade symbol. Not all specifications require a stamp, but when they do, the grade symbol and manufacturers mark will be permanently stamped on one end of each rod. When mass-produced all thread rod is not available due to a non-standard grade, or large diameter, the threaded rods are manufactured from scratch.
Here the process begins with saw cutting 20-foot lengths of steel round bar to a slightly longer overall length which allows the threading machines to grip the excess material and still thread the full length of the rod. Once the round bar has been cut, it is fed into a cut threading machine where the steel is physically removed to form the threads.
After the rods have been threaded, they are taken back to the saws to cut off the excess, unthreaded portion of the rod. From here the rods undergo the same chamfering, galvanizing, and stamping requirements that were demonstrated in the previous part of this video.
If you have questions about how all thread rod is manufactured visit www.portlandbolt.com