ASTM FM is an ASTM International standard for metric bolts, screws and studs that are used in general engineering applications. It is titled: Standard. ASTM F STANDARD SPECIFICATION FOR CARBON AND ALLOY STEEL EXTERNALLY THREADED METRIC FASTENERS. Metallica Metals India manufactures ASTM F Bolts, ASTM FM Bolts to your custom specifications, and we guarantee to meet your delivery schedule.
|Published (Last):||6 June 2006|
|PDF File Size:||5.59 Mb|
|ePub File Size:||12.44 Mb|
|Price:||Free* [*Free Regsitration Required]|
Customary Unit Fasteners Although metric fastener standards have been available in the US for more than 20 years, metric structural bolting is still not fully implemented in the United States.
The Industrial Fasteners Institute publishes an excellent summary of all metric fastener specifications in its Metric Fastener Standards. Both USCU and metric fasteners are marked so that iron workers and inspectors can quickly and easily verify that they are using the correct type of fastener zstm.
The sections that follow show the metric head markings and the figure below shows the markings for the most common types of USCU structural bolts. The most commonly used bolts in the USCU system were A bolts also called “common” or “unfinished” bolts and A bolts although A and A bolts are also sometimes used.
Astm F568 Grade 8.8.3 A Fasteners
Some common head markings are shown in the figure below. Every bolt head must be marked with the bolt type e. ASTM F defines materials used for manufacturing a broad category of fasteners with a wide variety of materials strengths. Some classes of bolts in the F family that are essentially equivalent to some common types of structural bolts are the following:.
Except for bolts smaller than 5 mm, all bolt heads are marked such that the property class is easily determined as shown in the figure below. The bolt head are also marked with a manufacturers mark e. Metric bolts are identified by their nominal diameter and the pitch. A mm diameter bolt with a 3-mm pitch is designated as an M24x3 bolt, the M indicating that this is a metric bolt.
Since there is only one pitch per diameter, it is common to refer to metric bolts only with the nominal diameter, for example M24 or M The nuts selected for a particular application must match the bolt for both material type and geometry. These bolts are often referred to as “common” bolts, “unfinished” bolts or “rough” bolts.
Technically they are not really structural bolts at all but are included here because they are often used in bearing connections where the loading is not large or is not critical to the performance or safety of the structure.
Such bolts might, for example, be used in a roof truss made up of angle sections in an industrial building or to connect brace members to main structural members. The proof loads and tensile strengths of Class 4. A bolts are intended to be tightened to nearly their proof load so that they develop significant bolt tension. Although AM bolts are made using A Class 8.
Astm F568 Grade 5.8 Fasteners
AM bolts have thicker and wider heads to more effectively distribute the head load to the piece and shorter shanks to keep the threads out of the load bearing aatm of the bolt. These of larger dimensions are referred to as “heavy hex” geometry. AM bolts are manufactured using material with a minimum yield strength of MPa and a minimum ultimate strength of MPa. The minimum ashm strength and the minimum bolt installation tension are shown in the table below.
The values in the minimum installation strength column are 70 percent of the values in the tensile strength column e.
A have a minimum yield strength of MPa and a minimum ultimate strength of MPa. When designing slip-critical connections it is very important that the fastener be tightened such that the bolt is in a slightly yielded astj. If a bolt is not tight enough, the bolt tension may not be enough to generate the required friction between the joined parts.
If the bolt tension is too large, the bolt may break.
ASTM F Bolts | ASTM F Hex Bolts | ASTM F Flange Bolts | ASTM F Studs
The ironworker installing the bolts must, therefore, get the bolt and nut tight enough to develop good friction in the joined pieces while not breaking the bolt. There are four basic methods for making sure a bolt have the proper amount of tension: The turn-of-the-nut method is the easiest and least expensive method for installing fasteners with the proper bolt tension.
The procedure generally works as follows. An iron worker tightens the bolt and nut as tight as possible using a spud 3 wrench or a pneumatic impact wrench.
A chalk mark or paint is then made on the bolt and nut. The bolt is tightened further by either hammering on the spud wrench or using a pneumatic impact wrench until the rotating part has rotated the required amount. The paint or chalk mark shows how far the part has rotated and the rotation is always measured relative to the rotation of the bolt. The number of turns past snug is dependent on the length of the bolt relative to its diameter and the geometry of the two surfaces.
The previous table shows the number of rotations for a variety of bolt lengths for flat horizontal surfaces. Most iron workers use pneumatic power wrenches, also called impact wrenches, to tighten bolts.
Calibrated wrenches can be set to stall at a specified torque thereby achieving the correct amount of bolt tension. Unfortunately, calibrated wrenches need to be calibrated at least every day since they tend to lose their calibration relatively quickly. Tension Indicating Bolts An indirect way to verify that a bolt has been properly tightened is to use tension indicating bolts like the one shown at the right.
This type of bolt is tightened with a special pneumatic wrench — one face of the wrench tightens the nut and the other holds the torque pattern head shown asym the right side in the figure. When the bolt is tightened to the proper load, the right end of the bolt shank snaps off. An ironworker would simply keep tightening the bolt until the tip breaks off and an inspector could easily verify that the bolt was properly tighten by ensuring that the tip is missing.
Direct tension indicators are special washers with grooves on one face. As the bolt is tightened the groves on the washer flatten out. An iron worker or inspector knows that the correct tension has been achieved when the gap between the washer and the piece will no long accept a gauge of a specified thickness.
The washers are said to directly indicate the tension since they have a know crush load. With the exception of the calibrated wrench method where the stall speed is set, the tension in the bolt is not directly measured. In fact, it is not necessary to be too careful about achieving some specific amount of tension as long as the bolt is in the yielded condition.
If the bolt is over tightened it will probably break in which case the iron worker simply needs to remove the broken bolt asm install a new one. The term “spud” wrench is a contribution of Irish-American iron workers. A spud wrench is a hand wrench with astj grip at one end and a long tapered handle at the other. The tapered handle is similar to a sailor’s marlin astj and is used to jamb into a series of holes to help align the holes before inserting the bolt.
The name aztm comes from the Gaelic word for a digging stick, “spaid.
Some classes of bolts in the F family that are essentially equivalent to some common types of structural bolts are the following: There are three types of AM bolts: Type 1 — a general-purpose medium carbon steel materials, Type 2 — a low-carbon martensite steel for atmospheric temperature applications, and Type 3 — a weathering steel suitable for use with sections or plate made using ASTM A weathering steel.
Turn-of-the-Nut Method The turn-of-the-nut method r568 the easiest and least expensive method for installing fasteners with the proper bolt tension.
Calibrated Wrench Method Most iron workers use pneumatic power wrenches, also called impact wrenches, to tighten bolts. Direct Tension Indicator Method Direct tension indicators are special washers with grooves on one face.