How a Bolt is Made

Follow an order through our shop and see how we make bolts.

Video Transcript

Hello! My name is Al Fogel and I’ve been the Operations Manager here at Portland Bolt since 1987.

This is an inch and a quarter diameter by 48 inch long, galvanized F1554 grade 36 hex head anchor bolt. We just completed 356 of these anchor bolts for the Caney River Substation project in Howard, Kansas.

We’ve been manufacturing bolts like these by hand since 1912 and we would like to take you through our shop to show you how a bolt like this is made.

The first labor operation in the manufacturing of any bolt is to cut the round bar to length. Our Peddinghaus shears function much like a guillotine and chop the steel, rather than using a saw blade to cut through it. We are capable of shearing round bar up to 2 inches in diameter and up to 100″ in length. Bolts that are larger in diameter or longer in length are band saw cut.

Next, A hex head is hot-forged on one end of the steel rod. An induction heating coil heats the end of the round bar to approximately 2000 degrees Fahrenheit. A National Upsetter is used to forge the heated end of the rod into a hex shaped head. Gripper blocks clamp the round bar securely in place while a plunger or die compresses the heated end of the rod, reshaping it into the hex head configuration. A second position in the gripper block is used to stamp the head with the manufacturer’s logo and grade symbol when required. The hex head of this anchor bolt will be embedded in the concrete and is intended to provide pull-out resistance.

High speed cutting blades apply a chamfer to the ends of the bolts prior to threading. This beveled end will help facilitate easy assembly of the nut once the bolts have been threaded and galvanized.

Landis threaders are used to cut 8″ of thread onto the end of these anchor bolts. Rotating heads contain chasers which cut away steel from the round bar to produce the threads. A constant stream of cutting oil is applied to reduce friction and prevent overheating. Threads are gauged by the threading operators to ensure conformance to dimensional tolerances.

The bolts must be pickled prior to galvanizing. This process cleans the bolts and prepares the surface of the steel to accept the zinc. Parts are first submerged in caustic soda which removes cutting oil and other organic materials that accumulate during the manufacturing process. The bolts are then rinsed and submerged in sulfuric acid, which removes any scale from the bolts and etches the surface of the steel. The bolts are rinsed again and then submerged in flux which is a chemical that assists in the bonding of the zinc to the steel.

After pickling, bolts are placed in racks and lowered into a 12 foot long x 4 foot wide x 7 foot deep tank of 840 degree molten zinc. The bolts remain in the zinc between 2 to 4 minutes. When the bolts are removed from the zinc, they are spun in a high speed centrifuge to remove excess zinc from the threads. Due to the proprietary nature of this process, we have not included it in this video.

Finally, the bolts are cooled in quench tanks so they can be inspected and packaged as soon as they are removed from the galvanizing tank. Blue paint is applied to the threaded end of F1554 grade 36 anchor bolts to identify the grade, as is required by the ASTM specification.

Bolts are banded to pallets, shrink wrapped, and clearly labeled. The morning after your order leaves our facility you will receive an email that contains shipment tracking information in addition to a copy of the mill test reports. Portland Bolt provides complete certification documents free of charge with every order.

Portland Bolt products ship nationwide and internationally. Refer to this page of our website to learn about the geographical distribution of the bolts we manufacture.