The answer is yes, however, there are several issues to consider to avoid liability. For this discussion, we will assume a requirement for threaded rebar as follows:
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#8 x 48&#; long A615 grade 60 rebar with 8&#; thread one end.
Rebar is short for &#;reinforcing bar&#; and often used in concrete foundations to strengthen the concrete. It is held in place by systematic ridges or deformations in its surface that allow the concrete to &#;grip&#; the bar better than plain round bar. These deformations are a great asset in the masonry applications, but hinder the usefulness of rebar as a threaded fastener.
Rebar gauges (diameter of the bar) are measured in eighths of an inch. For example, #8 rebar is essentially 1&#; diameter (8 x 1/8&#; = 8/8&#; or 1&#;).
Why can&#;t you just put threads on rebar?
Rebar cannot simply be cut threaded to the nominal diameter. This is due to the diameter difference between the major diameter of UNC threads and the diameter inside the deformations. The diameter inside the deformations is less than the minimum allowable major thread diameter. This will lead to incomplete threads and the liability that comes with product not meeting dimensional tolerances. As an example, the diameter on #8 rebar between the deformations is .960 and the minimum allowed major diameter on 1&#; threads is ..
How to properly cut thread rebar
The only way to correctly thread rebar is by turning down, or milling the end of the rod so that it is the proper size and shape to be threaded. This is done by removing the outer layer of the bar until the diameter is equal to the deepest deformation on the bar, leaving a smooth surface to thread. The smaller diameter of the threaded portion means that a larger size of rebar will have to be used and turned down in order to have threads that are the correct nominal diameter. If we go back to our example rebar above, we would need to use #9 rebar, instead of #8 in order to have proper 1&#; UNC threads.
Things to keep in mind when ordering threaded rebar
In cases where plans call for threaded rebar, it is essential that the engineer or detailer specify the diameter of thread needed on the bar, since cut threading a #8 rebar will not result in a complete 1&#; UNC thread. When thread type is not specified or ambiguous, Portland Bolt makes the assumption that the design requires a 1&#; thread and when cut threading, will use a #10 bar to produce a fully functional 1&#; &#; 8 threads per inch Unified National Coarse thread as opposed to cut threading a #8 bar which results in a 3/4&#; &#; 10 thread per inch finished product.
As opposed to cut threading, the threads on rebar can also be produced through a roll threading process. For the differences and limitations of roll threading versus cut threading, refer to our FAQ discussing roll threading versus cut threading. Keep in mind that roll threading equipment is limited in the marketplace and many companies that produce threaded rebar will not have the equipment available to roll threads. Most machine shops and smaller scale bolt manufacturing companies only have equipment that is capable of cut threading.
Unlike the cut thread example above, rebar can be turned to the pitch diameter (.912&#; in our example using #8 rebar) and rolled back up to produce a fully functional, dimensionally correct 1&#;- 8 UNC thread. Since some roll threading equipment has diameter and length limitations, rolling threads on rebar is sometimes not possible. Again, the thread dimension in addition to the size of the rebar should be specified.
To specify threaded rebar properly, our inquiry for this example should read as follows:
#8 (1&#;-8 UNC) x 48&#; long A615 grade 60 rebar with 8&#; thread one end.
Here are some of the important questions you will need to ask before buying any rebar couplers:
Strength and slip tests should be carried out according to ISO . One should always request strength, slip test reports and product certifications to ensure fitness for purpose. Approved by CARES and CREAM certifications, our MOMENT JoinTec Coupler is compliant with ISO as well as most of the international code of practice and exhibits superior cyclic performance. It is designed to withstand an ultimate tensile strength of up to 700 MPa, thus resulting in Bar Break performance on most of the rebar available on the market.
Each rebar coupler should be marked with symbols to trace it back to the raw material and production batch data. Good suppliers should have detailed process flow control with accurate manufacturing drawings, hold points and QAQC measures. Process flows ensure continuity of production and consistency in quality. MOMENT rebar couplers come with an embossed serial number, ensuring that full traceability exists throughout the manufacturing process from the mill, through machining, processing and packaging to supply.
Chamfered edge helps to cope with axial misalignment, providing a positive alignment locking connection thus providing load path continuity. It is also safer to install a chamfered coupler, especially when hand tightening a parallel threaded rebar coupler during installation.
The use of a fully automated CNC machine ensures a highly accurate rebar coupler. This not only ensures that the thread is located centrally in the coupler, therefore avoiding unwanted bending moments, but also that well-matched threads were produced consistently when compared to manual tapping, where the accuracy and quality are highly dependable on the operator.
The end of a bar has to be strengthened (normally cold-worked) to ensure that any reduction in the tensile (root thread) area of the original bar does not compromise the overall performance of the coupling, therefore making this type of coupler ideal in geographical areas prone to earthquakes where the formation of plastic hinges is essential for structural robustness. MOMENT rebar coupler system is supported by 3 high-productivity machines which prepare each bar in sequence: clean square cut, cold working of the bar end and then threading.
It is important to purchase rebar couplers from providers who have a team of engineers ready to provide assistance from design through to the completion of your development, eliminating the typical problems, surprises and costly delays. At Leviat, our qualified engineers offer additional services to our customers from technical support, product adaptation to installation, allowing customers to reach higher productivity with less hassle at construction sites.
Always request for the project reference list along with the types of products and the quantity supplied, this will help you to make an informed decision and to mitigate risk before making the choice.
MOMENT rebar coupler has been the market leader of the mechanical splice systems in Asia since . Our rebar couplers have been delivered to a diverse range of projects from national government projects, buildings, transportation infrastructures, utility infrastratures to oil and gas sectors. One may always refer to our project references and clients&#; testimonials on our website.
For more information, please visit dia 25mm threaded rebar for South Africa.
In conclusion, never compromise on quality and safety, it is always advisable to select the rebar coupler with the highest standards of quality and conformance to ensure its suitability regardless of the service conditions.
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