No, they are not. It is true that galvanizing adds a thickness to the threads of a bolt, which makes it imperative that they be spun in a centrifuge to remove the excess zinc from the threads. This is why it is so important that pole line hardware be galvanized via a galvanizing line specially tailored towards threaded fasteners. Chasing the threads is not only a bad idea, but it is prohibited in section 5.4.1 of the ASTM F2329, which covers the requirements of galvanizing threaded fasteners. If bolt threads are chased, they can remove too much zinc, leaving the threads bare and susceptible to corrosion. It can also remove steel, which can result in fastener threads being out of tolerance. For more information, take a look at this write up on galvanized bolts and chased threads.
- Are pole line fastener threads chased after galvanizing to provide a proper nut fit?
- Do pole line machine bolts have the same thread lengths as your “off the shelf” bolt?
- Are pole line fasteners always galvanized?
- Do all pole line fasteners have an added semi-cone point?
- What are pole line fasteners used for?
- What is the length of the added semi-cone point required for headed pole line fasteners, rods and double-arming bolts?
- Are pole line fasteners available in high strength grades?
Are pole line fastener threads chased after galvanizing to provide a proper nut fit?
Do pole line machine bolts have the same thread lengths as your “off the shelf” bolt?
Pole line machine bolts that are short in length (up to 3″) have the same thread length as a standard, “off the shelf” bolt, however when they reach longer lengths, they have longer thread lengths specific to their application. Below is a chart showing how the thread lengths differ depending on the bolt size.
|*Bolts shorter and/or smaller than those listed in the table shall have minimum thread lengths in accordance with American National Standard for Square and Hex Bolts and Screws, B18.2.1*|
|Diameters||Bolt length||Thread length|
||4" up to less than 8"||3"|
||8" up to less than 12"||4"|
||12" and over||6"|
Are pole line fasteners always galvanized?
Due to the exposure to outside elements, pole line hardware is required to be hot dip galvanized. All pole line hardware has this requirement, not just the fasteners. When galvanizing bolts, it is critical that the bolts be galvanized in a system set up specifically for threaded fasteners to ensure clean threads for a proper thread fit. Pole line fasteners are galvanized per ASTMF2329 and ASTM A153.
Do all pole line fasteners have an added semi-cone point?
Pole line fasteners, such as machine bolts, washer head bolts, double arming bolts and double end bolts, often have an added semi-cone point on the threaded end of the bolt. This is to provide easy installation into a wooden member without the threaded end of the bolt getting snagged on the wood. According to IEEE Standard C135.1-1999, “Machine bolts and double arming bolts that are 1/2″, 5/8″ and 3/4″ in diameter and are 8″ in length or longer shall have semi-cone points.” Larger diameters may require semi-cone points as well as bolts shorter than 8″, depending on the application. There are some configurations of pole line hardware which do not need a semi-cone point added, such as A325 structural bolts, bent bolts, and clamp rods.
What are pole line fasteners used for?
Although there are many types of pole line hardware, the actual fasteners are used to hold together wooden cross arms, which are then installed on to the top portion of utility poles. Different fasteners such as headed bolts and rods and bent bolts serve different purposes within the cross arm assembly, but are all integral parts to make up one entire assembly.
What is the length of the added semi-cone point required for headed pole line fasteners, rods and double-arming bolts?
Pole line fasteners often require an added semi-cone point on the threaded end. This eases entry into the pre-drilled holes in the wooden members that they are going through. Not all pole line fasteners have added semi-cone points, however. The common items that have an added semi-cone point are hex head machine bolts, square head machine bolts, washer head bolts, double end bolts and double arming bolts. Although it can differ depending on who manufactures them, the length of the semi-cone point is approximately 1/2 of the diameter of the bolt. In other words, a 1/2″ diameter machine bolt will have a 1/4″ added semi-cone point on the end and a 1″ diameter machine bolt will have a 1/2″ added semi-cone point.
An important thing to keep in mind when specifying a particular length of bolt is that the semi-cone point length is not included in the overall bolt length call out. For example, if a 1″ x 18″ long square head bolt is required, it is called out as 1″ x 18″, not 1″ x 18-1/2″, though the total length of the bolt (including the point) will be 18-1/2″. Double end bolts and double arming bolts have an added semi-cone point on each end. Double arming bolts will sometimes have a 1/4″ semi-cone point added to each end regardless of the diameter of bolt, but more often than not, each semi-cone point would be 1/2 of the diameter.
Are pole line fasteners available in high strength grades?
Pole line fasteners are normally manufactured to ASTM A307A, which is a low carbon mild steel, however there are occasions where the question is presented on the availability of high strength graded pole line fasteners. High strength pole line fasteners are not commonly required and would need to be specially manufactured and heat treated to a given specification on a per order basis. An exception would be ASTM A325 heavy hex structural bolts, which are typically available off shelf and would not need to be specially made. This is assuming that the size of A325 required is a standard, off the shelf size.
An example of a common pole line fastener required to be made from a higher strength material would be what are referred to as bent bolts (or bent rods). Although these parts are more commonly made to ASTM A307A, there are times when they are called out as being made from 1045 steel. 1045 is only a raw material however and is not specific to any particular ASTM specification. As a result, they do not need to be heat treated, however they do require a stress reliving process after the bending has been performed. Again, although these parts have been specified as 1045, it is much more common to see them made to ASTM A307A.
As with fasteners in many industries, some are readily available whereas others need to be specially manufactured on a per order basis. This is the case with low strength graded pole line fasteners as well as high strength; however it is much less common for pole line fasteners to be required in high strength grades. If a high strength grade is specified, the bolts would need to be manufactured by a company that not only has the ability to forge, point, thread and galvanize the bolts, but also the ability to heat treat the bolts to the required specification.