Steel Manufacturing Blog: Keeping it Steel

F1554 Anchor Bolt Threads / UNC 1A, 2A, 3A

Posted on Wed, Nov 13, 2013 @ 10:16 PM

Note: The ASTM document describing Anchor Bolt manufacturing standards is F-1554. The current version is F 1554-07a. 

Regarding thread class, quoting directly from ASTM 1554-07a, "Class 2A shall be furnished when the class is not specified."

Typically the prints we see spell out all relevant criteria for bolt manufacturing but rarely mention threading class. As shown above F1554-07a takes care of that but what does 2A mean?

In bolt threading the externally threaded item (the bolt) is the A class. The internally threaded nut is the B class. Class indicates tolerance. Class 1 is the loosest fit. It is generally designed for applications where a fast installation is desired and/or the working environment would make tighter fits impractical. An example of the would be for bolts securing concrete forms. Often All Threaded Rod is manufactured to a 1A tolerance.

Class 2 fit is the general construction industry standard. It's anchor bolt tolerance is 32% tighter than the 1A fit. This allows for a more secure fit yet still provides enough leeway to accomodate field conditions such as damage or grit in the threads. Properly done, an anchor bolt threaded to a 2A fit can have the usual rust and light contaminents on the threads and still have the nut thread by hand until it bottoms out.

The Class 3A is used for machine bolts or other applications where a tighter fit is required. Usually this means the working environment will not create problems in the thread fit, and installation time is not an issue. Tolerance is reduced by 25% compared to the 2A fit.

F1554 Anchot BoltThe chart to the left (fig. 1) displays how the desired fit is achieved. As the Class goes up the tolerance decreases. Most of the decrease comes from raising the lower tolerance. With the matching nut the tighter fit is achieved by lowering the upper tolerance.

  

For addition information regarding F1554 Anchor Bolts;

Galvanizing vs. Hydrogen Embrittlement

Anchor Bolt Bending

Anchor Bolt Page

 

View Our Anchor Bolts
 

Tags: F1554, Anchor Bolts, Bent Anchor Bolts, Cut Thread

Tapered Steel Wedges

Posted on Wed, Nov 06, 2013 @ 10:28 PM

In a previous article we described the process of making Made To Order Steel Wedges. See Steel Wedges - Made To Order This article will deal with the specifics of manufacturing the Russian Wedge, so called because of the unique Knock out Block at the large end. (see bottom right photo)

The Steel Supply Company was contacted by an oil field drilling company working in Russia. The extreme cold temperatures forced limits on how long their workers could be outdoors and how effective they could be. While driving a steel wedge is a straightforward process, removing it is often more time consuming. The steel block at the large end allows this wedge to be quickly driven out with a sledge hammer or slide hammer.

Most made to order steel wedges are made 2 at a time. It begins with a solid steel block that is slightly larger than the two wedges will be when set reciprocally. The block is cut diagonally and the rudimentary form is set. The Russian Wedge made this an ineffective method because of the knock out block.

To manufacture this as a solid piece required the following steps.

Steel Wedge - Made to OrderSteel Wedge - Made to Order1) These wedges were still made two at a time. Pilot holes were drilled and a band saw blade passed through. Cutting was then guided by hand. This allowed for working around the Knock Out Block. (fig. 1 and fig. 2.)

  

  

2) The result is two roughed out wedges. Note they are both still oversized to allow for machining. (fig 3 below left.)

3) The wedges are then set in a shaper. This machine is usually used in gear manufacturing shops for removing the metal stock between the gear teeth. It is effective in the wedge manufacturing process because, as shown in fig. 4, it can accept two wedges at a time, it can be set to remove the stock to within several thousanths of the finished dimensions, and most important it can run un-attended.

 

Steel Wedge - Made to Order

Once the shaping process is complete the wedges are milled to their desired specifications that will leave a smooth machined surface. (fig. 5) The final step is deburring, which in this case was done by hand.

Steel Wedge - Made to Order
 Tapered Steel Wedges (click)
 Stock Size Steel Wedges (click) 

Request a Quote Now

Tags: Wedges, Steel Wedges, Steel Wedge, Steel Wedges Made To Order

Galvanizing vs. Hydrogen Embrittlement

Posted on Tue, Nov 05, 2013 @ 06:38 PM

First this article will describe the condition known as Hydrogen Embrittlement. Further below it will get into how and why Hydrogen Embrittlement is an important factor when Galvanizing any steel or alloy product. 

Hydrogen embrittlement occurs in steel when individual hydrogen atoms enter voids in the steel and combine with each other to form hydrogen molecules. The formation of these molecules creates outward pressure. If the product involved is an anchor bolt this pressure can reduce the pull strength of the steel. (fig 1)

F1554 Anchor Bolt

The normal voids mentioned above tend to run a long the grain lines in the steel. That would be where the hydrogen molecules accumulate. If a crack should occur, it will usually follow the contour of the grain line also. In the photo below, which is magnified 1500 times, the cracks that occured are clearly visible. 

F1554 Anchor BoltWhile there can be several causes, to the structural steel fabricator the significance of Hydrogen Embrittlement becomes most relevant during the Hot Dip Galvanizing process. Prior to being immersed in molten zinc the steel is prepared in a series of acid baths known as Pickling. These acids contain hydrogen atoms that can migrate into the steel and begin the process described above. The heat of the actual galvanizing process can also be a factor in the process.

As it applies to Anchor Bolts this condition is generally not a factor in standard grades of round bar. Hydrogen Embrittlement becomes a factor when galvanizing higher strength steel, with tensile strength in excess of 150 ksi, such as A-490. ASTM A-143 states Hydrogen Embrittlement becomes a concern when the tesile strength of the steel exceeds approximately 150ksi. Of the three grades of round bar spelled out in the ASTM Anchor Bolt specifications (F1554) only the strongest, Grade A-105 approaches a tensile strength of 150 ksi.

Tags: F1554, Anchor Bolts, Bent Anchor Bolts