The combination of durability and versatility has made threaded rods essential tools across several applications common within manufacturing and construction that require heavy loads to be lifted or moved. In this blog, we will address the most frequently asked questions about threaded rods.
What Are Threaded Rods Used For?
In short, threaded products are used to make something move or to hold something in place. Threaded rods, along with a mating part, such as a nut, flange, or jack, provide a path for movement. While most think of small bolts, screws, and studs as fasteners, the category of fasteners includes large threaded products as well. Serving as an anchor bolt, tie rod, or structural support, a fastener can be 2” in diameter and 12” in length.
How Are Threaded Rods Measured?
A precision product has many measurable dimensions – pitch diameter, minor diameter, flank angle, root radius, length of thread, and overall length – to ensure that every threaded rod is within the limits set by internationally recognized standards as well as customer specifications.
When ordering or calling out a specification, a standard product description looks like this:
|Diameter||Thread Pitch||Length||Thread Type||Material|
|3/4"||-||10||x||3 ft||Acme||304 Stainless|
How Much Weight Can a Threaded Rod Hold?
The weight capacity of a given threaded rod is highly dependent on its application, material tensile strength and hardness, cross-sectional distance of the threaded rod, and distance between the load and fulcrum. Equations for such calculations may be found in the Machinery’s Handbook and other reference sources.
What Is Torsional Strength?
The torsional strength of a material is its ability to resist failure under a twisting load.
Are Rolled Threads Stronger Than Cut Threads?
Yes! Rolled threads have up to a 30% higher tensile strength compared to cut threads. The process of roll threading work-hardens many of the materials from which they are made, so they are also harder than cut threads. Additionally, the burnished surface of rolled threads increases the material’s resistance to fatigue.
What Are the Common Class Fits of Threaded Products? What Are Their Main Characteristics?
In regards to Acme threaded products, there are two classes to which we fabricate threaded bars: 2C and 2G. The “G” and “C” refer to "General Use" and "Centralizing," respectively. 2C is the preferred choice in applications involving side loads, as the limited tolerancing and reduced clearance between major diameters of screw and nut act as a bearing to counter the wedging action inherent to their 2G counterpart.
2G class threaded bars perform well in a wide range of applications in terms of transitioning rotary motion to linear motion. The wedging action seen with 2G Acme threads may be an advantage in designs subject to normal force, as it acts as a brake where the load is not great enough to overcome the frictional coefficient of the two materials involved. In addition to the tolerancing of major diameters between “C” and “G” class Acme threads, in accordance with ANSI/ASME B1.5, the accuracy of thread lead is 1/3 greater with “C” as compared to “G.”
As it pertains to unified thread forms, Keystone Threaded Products offers classes 2 and 3. This is true with both internal and external threads. Class 3 has a limited range of tolerance compared to Class 2.
What Are the Common Materials Used to Create Threaded Products? And What Are Their Main Characteristics?
Our most popular material is our Key Alloy B7. B7 is a molybdenum and chromium alloy with a high tensile strength (100 ksi min.) and medium hardness per ASTM A193. Key Alloy B7 is not easily welded and must be subjected to thermal treatment before and after welding to avoid cold cracking. This type of material has an excellent strength-to-weight ratio, and work hardens during the thread rolling process. B7 retains structural integrity at elevated temperatures and under heavy loads; it is used in specialty fastener manufacturing.
Our second-most-popular material is a low carbon 1018 cold finished steel. 1018 CF is one of the most commonly used steels in fasteners and other machine parts, as it is very easy to cold form, machine, and weld. 1018 CF lends itself well to high-volume production due to these attributes.
1018 CF and Key Alloy B7 are both carbon steels, and when subjected to the elements, will oxidize without surface treatments. To combat oxidization, we will typically recommend using a zinc plating or black oxide surface treatment to extend the component’s useful life.
316 austenitic stainless steel is another common material type chosen by our customers, as it offers a high degree of hardness and tensile strength (>74.5 ksi) with a corrosion resistance high enough to eliminate the need for surface treatments. Our customers with marine applications prefer this material to other chrome-nickel steels, as it is especially resistant to chemicals and chlorides.
304 CRES is another austenitic stainless material that we often use to roll threaded components. Like 316, it has high tensile strength and hardness as well as high corrosion resistance. 304 CRES is somewhat tougher than other stainless steels such as 316, although it has a lower resistance to chlorides. It is used extensively in aerospace applications.
6061 T6 aluminum is another common material from which we make threaded products. 6061 T6 aluminum, while softer than the aforementioned steels and stainless steels, has a high strength-to-weight ratio, as it is much less dense and therefore much lighter.
Keystone Threaded Products offers its allthread in other materials, such as titanium, Inconel, and other grades of mild and low-carbon steels. These are less common than those mentioned above.
As for nuts, we offer heavy hex nuts made from mild steel, 316 and 304 stainless, as well as 10L12 steel. We offer round nuts in 673 and 932 bronze as well as Class 40 gray iron. Both bronze types have excellent corrosion resistance and good wear resistance. These pair well with most of the materials from which our allthread is fabricated.
What Are Keystone’s Size Capabilities?
Keystone has the capability of rolling bars up to 14–16" in diameter and lengths up to 40'.
What Applications Are Trapezoidal Threaded Bars Typically Used In?
Trapezoidal threaded bars are the metric equivalent to those with an Acme thread form. These are typically used in applications where there are large loads expected. These applications include lead screws, lift screws, and vise screws. Trapezoidal threaded products are used primarily in applications outside of the U.S. and Canada, as these countries use the metric measurement system.
What Applications Are Acme Threaded Bars Typically Used In?
Acme threaded bars are used in similar applications to their trapezoidal counterparts. These applications include lead screws, lift screws, and vise screws. Acme threaded products are primarily used within the U.S. and Canada, as these countries use the imperial measurement system.
What Applications Are Metric Threaded Bars Typically Used In?
Much like trapezoidal thread forms, other metric thread forms are used primarily outside of the U.S. Metric threads have the same thread profile as their imperial counterparts (unified threads), only measured with metric units as opposed to inches. These threads are common among fasteners, anchor bolts, automotive components, and other general assemblies.
What Applications Are Unified Threaded Bars Typically Used In?
Unified threaded bars are used to fabricate such components as fasteners, anchor bolts, and automotive components. These are identical to metric threaded bars except for being measured in imperial units (i.e., inches).
If you have additional questions about threaded rods, contact us today!