FAQs
General Questions
Torsional strength describes a material’s resistance to a twisting load, such as torque on a driveshaft.
Yes, typically rolled threads are 10-20% stronger from the cold working and displacement of the material.
1 to 50 depending on diameter. For more detailed information, please visit our Threaded Rod products page.
Proof load represents the usable strength range. It is the maximum stress (load tension) that a metal can resist without permanently deforming (as in elongating).
Shear strength is the maximum load that can be supported prior to fracture when applied at a right angle to the fastener’s axis.
Hardness is a measure of a material’s ability to resist abrasion and indentation.
Major Diameter is the largest diameter of a screw thread. Whereas, Minor Diameter is the smallest diameter of a screw thread.
Annealing is the process of heating, then gradually cooling a material to increase its ductility and to remove internal stresses, making the hardness more consistent.
It is domestically manufactured, but not necessarily melted in the U.S.A. We purchase steel from several sources, some domestic and some overseas. We draw, straighten, cut, and thread rod in our plants here in the U.S.A.
Technical Question
Generally speaking, yes, AISI 1018 should meet the requirements of both A36 and A307, except for heavy plate over ¾” thick. However, these ASTM specs will require mechanical testing by a certified lab to be sure the mechanical properties are in accordance with the respective specification. Chemistry is only one part of an ASTM specification.
Yes, certain grades can become magnetic. Ferritic and some martensitic grades are weakly interactive with magnetic fields, while the austenitic grades are not.
These terms refer to the crystal structure of the metal. Regular steel (non-stainless) would be considered “ferritic” because the room-temperature microstructure is comprised of a mix of ferrite and pearlite. Ferrite is soft and ductile, while pearlite is hard and brittle. As the overall content of carbon increases, the proportion of pearlite becomes higher and the bulk strength increases. Austenite is a high-temperature phase of plain steel, which recrystallizes into ferrite/pearlite around 1425°F (depending on chemistry), below which ferrite becomes the more stable phase. Certain alloy elements, most notably nickel, are able to stabilize the austenite phase down to room temperature. This is the major difference between 300 and 400 series stainless steel; 300-series grades contain enough nickel to stabilize austenite at room temperature and hence are termed “austenitic” grades. Martensite is a meta-stable phase that is formed when high-temperature austenite is quickly quenched below a critical temperature (that changes depending on chemistry). It is characterized by its extremely high strength, low fracture resistance, and low ductility. It can be held at an intermediate temperature for various times, in a process called tempering, to reduce strength while vastly improving toughness and ductility. Martensite can be achieved in both alloy and stainless steels.
Class 1A is a loose commercial fit for easy assembly and disassembly.
Class 2A is a medium fit.
Class 3A is a tight fit used where a closed fit between mating parts is required.Thread classes are distinguished from each other by the amount of tolerance and allowance specified. External threads are designated with the suffix “A”, internal (nut) threads with “B”.
No, when heat is reapplied to heat-treated rod, it is possible the physical properties will be changed. Welding B7 is NOT recommended.
Tensile Strength is the maximum stress (usually represented in PSI) that a material can withstand while being stretched or pulled before failing or breaking. Whereas, Yield Strength is the stress a material can withstand without permanent deformation or a point at which it will no longer return to its original dimensions (by 0.2% in length).
Pitch is the distance from a point on the screw thread to a corresponding point on the next thread measured parallel to the axis. Pitch Diameter is the simple effective diameter of screw thread, approximately halfway between the major and minor diameters.
18-8 stainless is an industry term that stands for any stainless alloy that consists of approximately 18% chromium and 8% nickel.
GRADE 5 ASTM A193 B7 GRADE 8 TENSILE STRENGTH 120,000 PSI
minimum125,000 PSI minimum
1,100°F tempering temp150,000 PSI
minimumYIELD STRENGTH 92,000 PSI
minimum105,000 PSI
minimum130,000 PSI
minimumROCKWELL HARDNESS C25-C34
C26-C32
C33-C39
SOURCE: www.AATProd.com304 Stainless Steel
• Provides excellent corrosion resistance.
• Ideal for chemical, marine, and other corrosive environments.
• Non to slightly magnetic.
• Most common stainless for fasteners.Note: when cycled above 850 degrees F, 304SS gets chromium depletion (by a process called carbide precipitation); chromium combines with the carbon to form chromium carbide, which is not corrosion-resistant.
316 Stainless Steel
• Contains molybdenum for more corrosion-resistance than 304SS.
• Withstands many chemical and solvents, even pitting caused by chlorides (such as in paper mills).
• Non to slightly magnetic.Hydrogen embrittlement occurs where hydrogen migrates out of its normal structure in steel, causing a failure of reliability to the metal’s normal properties.
The failure may be immediate in use or may occur in a delayed manner. The primary problem in the industry is a specific form of hydrogen embrittlement, called Hydrogen Stress Cracking (HSC), a result of hydrogen absorption.
Ferrous alloys, especially those with relatively large quantities of carbon are prone to hydrogen embrittlement.
Several of the American Society of Mechanical Engineers (ASME) standards appendices contain two different types of gauges for determining part straightness. One gauge is an attribute-type of thread runout gauge consisting of a special threaded ring gauge attached to a cylinder which is set with a special setting master.
The second gauge is an attribute-type camber or bow measuring gauge consisting of a base plate with one stationary side rail and one adjustable side rail. The gap between the rails is set with a pair of micrometer heads.
The ASME B18 sub-committees are in the process of removing the thread runout gauge and leaving only the camber gauge in the various screw and bolt standards. This action is being taken because the sub-committee members feel the rail-type camber gauge is as likely to detect objectionably bent screws and bolts as well as the runout-type gauge, but the rail-type gauge is much more versatile and cost-effective.
Most of the ASME standards are consistent in their straightness specifications. Screws and bolts up to and including 12’ in length can be bowed 0.006” per inch of length. Parts exceeding 12’ can be bowed 0.008” per inch of length. If a user’s application requires a part straighter than these limits, it must specify the required straightness limits on the print and/or purchase order.
Manufacturing Questions
A449 is an ASTM specification covering “Hex cap screws, bolts and studs, steel, heat treated, 120/105/90 ksi minimum tensile strength, general use”. From ASTM: “This specification covers quenched and tempered steel hex cap screws, bolts, and studs having a minimum tensile strength. The fasteners are intended for general engineering use. Type 1 fasteners shall be plain carbon steel, carbon boron steel, alloy steel, or alloy boron steels conforming to the requirements. Type 3 fasteners shall be weathering steel and shall conform to one of the chemical compositions specified. Tensile strength, proof load, hardness tests, and axial tension tests shall be performed to conform to the specified requirements.”
Zinc plating or electroplating is a process where zinc is applied by using a current of electricity. It is a thinner coating than hot dip galvanizing.
Hot-dip galvanizing is a process of applying a protective zinc coating by dipping product in bath of molten zinc. Generally applied at 830 to 870 degrees, the zinc will bond with the steel.Yes. Other thread types that we manufacture are coarse thread (right & left hand), fine thread (right & left hand), and acme thread.
All America Threaded Products forms the majority of its threaded rod and bar products using the thread rolling process. Cold forming is the best description of this process. All America Threaded Products feeds a cylindrical steel blank of diameter between the minor and major diameter of the finished thread size, into hardened steel dies bearing the reverse thread form to the finished parts. All America Threaded Products “matches” the dies to produce the correct thread form. The rotating die threads penetrate the blank surface, forming the thread roots and displacing material radially outward to form the thread crests. There is no material removal or waste.
Passivation is the dissolving ferrous particles and impurities on stainless steel by treating it briefly with an acid and to produce a passive film on the surface after all forming operations are complete. The purpose is to improve the corrosion resistance of the surface.