Showing posts with label Machine Elements. Show all posts
Showing posts with label Machine Elements. Show all posts

British Standard Square and Hexagon Bolts

British Standard Square and Hexagon Bolts, Screws and Nuts.—Important dimensions of precision hexagon bolts, screws and nuts (BSW and BSF threads) as covered by British Standard 1083:1965 are given in Tables 1 and 2. The use of fasteners in this standard will decrease as fasteners having Unified inch and ISO metric threads come into increasing use.

Dimensions of Unified precision hexagon bolts, screws and nuts (UNC and UNF threads) are given in BS 1768:1963 (obsolescent); of Unified black hexagon bolts, screws and nuts (UNC and UNF threads) in BS 1769:1951 (obsolescent); and of Unified black square and hexagon bolts, screws and nuts (UNC and UNF threads) in BS 2708:1956 (withdrawn). Unified nominal and basic dimensions in these British Standards are the same as the comparable dimensions in the American Standards, but the tolerances applied to these basic dimensions may differ because of rounding-off practices and other factors. For Unified dimensions of square and hexagon bolts and nuts as given in ANSI/ASME B18.2.1-1996 and ANSI/ASME B18.2.2-1987 (R1999).

ISO metric precision hexagon bolts, screws and nuts are specified in the British Standard BS 3692:1967 (obsolescent) (see British Standard ISO Metric Precision Hexagon Bolts, Screws and Nuts), and ISO metric black hexagon bolts, screws and nuts are covered by British Standard BS 4190:1967 (obsolescent).

British Standard Screwed Studs.—General purpose screwed studs are covered in British Standard 2693: Part 1:1956. The aim in this standard is to provide for a stud having tolerances which would not render it expensive to manufacture and which could be used in association with standard tapped holes for most purposes. Provision has been made for the use of both Unified Fine threads, Unified Coarse threads, British Standard Fine threads, and British Standard Whitworth threads as shown in the table on page 1573. Designations: The metal end of the stud is the end which is screwed into the component. The nut end is the end of the screw of the stud which is not screwed into the component. The plain portion of the stud is the unthreaded length.

In general, it will be found that the amount of oversize specified for the studs will produce a satisfactory fit in conjunction with the standard tapping as above. Even when interference is not present, locking will take place on the thread runout which has been carefully controlled for this purpose. Where it is considered essential to assure a true interference fit, higher grade studs should be used. It is recommended that standard studs be used even under special conditions where selective assembly may be necessary.

British Standard Whitworth (BSW) and Fine (BSF) Precision Hexagon Bolts, Screws, and Nuts
British Standard Whitworth (BSW) and Fine (BSF) Precision Hexagon Bolts, Screws, and Nuts

Table 1. British Standard Whitworth (BSW) and Fine (BSF) Precision Hexagon Slotted and Castle Nuts BS 1083:1965 (obsolescent)
British Standard Whitworth (BSW) and Fine (BSF) Precision Hexagon Slotted and Castle Nuts

Table 2. British Standard Whitworth (BSW) and Fine (BSF) Precision Hexagon Slotted and Castle Nuts BS 1083:1965 (obsolescent)
British Standard Whitworth (BSW) and Fine (BSF) Precision Hexagon Slotted and Castle Nuts

Table 3. British Standard ISO Metric Precision Hexagon Bolts, Screws and Nuts
BS 3692:1967 (obsolescent)
British Standard ISO Metric Precision Hexagon Bolts, Screws and Nuts

Table 4. British Standard ISO Metric Precision Hexagon Bolts and Screws BS 3692:1967 (obsolescent)
British Standard ISO Metric Precision Hexagon Bolts and Screws BS 3692:1967 (obsolescent)

Table 5. British Standard ISO Metric Precision Hexagon Nuts and Thin Nuts BS 3692:1967 (obsolescent)
British Standard ISO Metric Precision Hexagon Bolts and Screws BS 3692:1967 (obsolescent)

You may see also the other related topics:
Metric Threaded Fasteners - List of Standard ANSI for Metric Screws
Unified Screw Threads - American Standard for Unified Screw Threads
Engineering Books - Mechanical Engineering Books

American National Standard of Small and Large Rivets

American National Standard Large Rivets
The types of rivets covered by this standard (ANSI B18.1.2-1972 (R1995)). It may be noted, however, that when specified, the swell neck included in this standard is applicable to all standard large rivets except the flat countersunk head and oval countersunk head types. Also shown are the hold-on (dolly bar) and rivet set impression dimensions.

All standard large rivets have fillets under the head not exceeding an 0.062-inch radius. The length tolerances for these rivets are given as follows: through 6 inches in length, 1⁄2- and 5⁄8-inch diameters, ±0.03 inch; 3⁄4- and 7⁄8-inch diameters, ±0.06-inch; and 1- through 13⁄4-inch diameters, ±0.09 inch. For rivets over 6 inches in length, 1⁄2- and 5⁄8-inch diameters, ±0.06 inch; 3⁄4- and 7⁄8-inch diameters, ±0.12 inch; and 1- through 13⁄4-inch diameters, ±0.19 inch. Steel and wrought iron rivet materials appear in ASTM  specifications A31, A131, A152, and A502.

American National Standard Large Rivets

American National Standard Small Solid Rivets
The types of rivets covered by this standard (ANSI/ASME B18.1.1-1972 (R1995)). In addition, the standard gives the dimensions of 60-degree flat countersunk head rivets used to assemble ledger plates and guards for mower cutter bars, but these are not shown. As the heads of standard rivets are not machined or trimmed, the circumference may be somewhat irregular and edges may be rounded or flat. Rivets other than countersunk types are furnished with a definite fillet under the head, whose radius should not exceed 10 percent of the maximum shank diameter or 0.03 inch, whichever is the smaller. With regard to head dimensions, tolerances shown in the dimensional tables are applicable to rivets produced by the normal cold heading process. Unless otherwise specified, rivets should have plain sheared ends that should be at right angles within 2 degrees to the axis of the rivet and be reasonably flat.

Rivets may be made of ASTM Specification A31, Grade A
steel; or may adhere to SAE Recommended Practice, Mechanical and Chemical Requirements for Nonthreaded Fasteners—SAE J430, Grade 0. When specified, rivets may be made of other materials.

ANSI/ASME B18.1.3M-1983 (R1995), Metric Small Solid Rivets, provides data for small, solid rivets with flat, round, and flat countersunk heads in metric dimensions. The main series of rivets has body diameters, in millimeters, of 1.6, 2, 2.5, 3, 4, 5, 6, 8, 10, and  12. A secondary series (nonpreferred) consists of sizes, 1, 1.2, 1.4, 3.5, 7, 9, and 11 millimeters.

American National Standard Small Solid Rivets

You may also refer to other related topics:

Rivet and Riveted Joints - classes and types of riveted joints 
Mechanical Engineering Books - useful related books

British Standard Metric Keys and Keyways

This British Standard, BS 4235:Part 1:1972 (1986), covers square and rectangular parallel keys and keyways, and square and rectangular taper keys and keyways. Plain and gib-head taper keys are specified. There are three classes of fit for the square and rectangular parallel keys and keyways, designated free, normal, and close. A free fit is applied when the application requires the hub of an assembly to slide over the key; a normal fit is employed when the key is to be inserted in the keyway with the minimum amount of fitting, as may be required in mass-production assembly work; and a close fit is applied when accurate fitting of the key is required under maximum material conditions, which may involve selection of components.

The Standard does not provide for misalignment or offset greater than can be accommodated within the dimensional tolerances. If an assembly is to be heavily stressed, a check should be made to ensure that the cumulative effect of misalignment or offset, or both, does not prevent satisfactory bearing on the key. Radii and chamfers are not normally provided on keybar and keys as supplied, but they can be produced during manufacture by agreement between the user and supplier. Unless otherwise specified, keys in compliance with this Standard are manufactured from steel made to BS 970 having a tensile strength of not less than 550 MN/m2 in the finished condition. BS 970, Part 1, lists the following steels and maximum section sizes, respectively, that meet this tensile strength requirement: 070M20, 25 × 14 mm; 070M26, 36 × 20 mm; 080M30, 90 × 45 mm; and 080M40, 100 × 50 mm.

At the time of publication of this Standard, the demand for metric keys was not sufficient to enable standard ranges of lengths to be established. The lengths given in the accompanying table are those shown as standard in ISO Recommendations R773: 1969, “Rectangular or Square Parallel Keys and their Corresponding Keyways (Dimensions in Millimeters),” and R 774: 1969, “Taper Keys and their Corresponding Keyways—with or without Gib
Head (Dimensions in Millimeters).”

Narrow V-belts Selection

Narrow V-Belts ANSI/RMA IP-22.—Narrow V-belts serve the same applications as multiple, classical V-belts, but allow for a lighter, more compact drive. Three basic cross sections—3V and 3VX, 5V and 5VX, and 8V—are provided, as shown in Fig. 1. The 3VX and 5VX are molded, notched V-belts that have greater power capacity than conventional belts. Narrow V-belts are specified by cross section and effective length and have top widths ranging from 3⁄8 to 1 inch. 

Narrow V-belts usually provide substantial weight and space savings over classical belts. Some narrow belts can transmit up to three times the horsepower of conventional belts in the same drive space, or the same horsepower in one-third to one-half the space. These belts are designed to operate in multiples and are also available in the joined configuration. 

Belt Cross Sections: Nominal dimensions of the three cross sections are given in Fig. 1.

Belt Size Designation: Narrow V-belt sizes are identified by a standard belt number. The first figure of this number followed by the letter V denotes the belt cross section. An X following the V indicates a notched cross section. The remaining figures show the effective belt length in tenths of an inch. For example, the number 5VX1400 designates a notched V-belt with a 5V cross section and an effective length of 140.0 in. Standard effective lengths of narrow V-belts are shown in Table 1.

Sheave Dimensions: Groove angles and dimensions for sheaves and face widths of sheaves for multiple belt drives are given in Tables 2a and 2b, along with various tolerance
values. Standard sheave outside diameters are given in Table 3.

Bearing Lubricants

Methods of Lubrication.—There are numerous ways to supply lubricant to bearings. The more common of these are described in the following.

Pressure lubrication, in which an abundance of oil is fed to the bearing from a central groove, single or multiple holes, or axial grooves, is effective and efficient. The moving oil assists in flushing dirt from the bearing and helps keep the bearing cool. In fact, it removes heat faster than other lubricating methods and, therefore, permits thinner oil films and unimpaired load capacities. The oil-supply pressure needed for bushings carrying the basic load is directly proportional to the shaft speed, but for most installations, 50 psi will be adequate.

Splash fed applies to a variety of intermittently lubricated bushings. It includes everything from bearings spattered with oil from the action of other moving parts to bearings regularly dipped in oil. Like oil bath lubrication, splash feeding is practical when the housing can be made oiltight and when the moving parts do not churn the oil. The fluctuating nature of the load and the intermittent oil supply in splash fed applications requires the designer to use experience and judgment when determining the probable load capacity of bearings lubricated in this way.

Oil bath lubrication, in which the bushing is submerged in oil, is the most reliable of all methods except pressure lubrication. It is practical if the housing can be made oil tight, and if the shaft speed is not so great as to cause excessive churning of the oil.

Oil ring lubrication, in which oil is supplied to the bearing by a ring in contact with the shaft, will, within reasonable limits, bring enough oil to the bearing to maintain hydrodynamic lubrication. If the shaft speed is too low, little oil will follow the ring to the bearing; and, if the speed is too high, the ring speed will not keep pace with the shaft. Also, a ring,revolving at high speed will lose oil by centrifugal force. For best results, the peripheral speed of the shaft should be between 200 and 2000 feet per minute. Safe load to achieve hydrodynamic lubrication should be one-half of that for pressure fed bearings. Unless the load is light, hydrodynamic lubrication is doubtful. The safe load, then, to achieve hydrodynamic lubrication, should be one-quarter of that of pressure fed bearings.

Wick or waste pack lubrication delivers oil to a bushing by the capillary action of a wick or waste pack; the amount delivered is proportional to the size of the wick or pack.

Lubricants: The value of an oil as a lubricant depends mainly on its film-forming capacity, that is, its capability to maintain a film of oil between the bearing surfaces. The filmforming capacity depends to a large extent on the viscosity of the oil, but this should not be understood to mean that oil of the highest viscosity is always the most suitable lubricant. For practical reasons, an oil of the lowest viscosity that will retain an unbroken oil film between the bearing surfaces is the most suitable for purposes of lubrication. A higher viscosity than that necessary to maintain the oil film results in a waste of power due to the expenditure of energy necessary to overcome the internal friction of the oil itself.

Grease packed in a cavity surrounding the bushing is less adequate than an oil system, but it has the advantage of being more or less permanent. Although hydrodynamic lubrication is possible under certain very favorable circumstances, boundary lubrication is the usual state.


Classes and Types of Riveted Joints
Riveted joints may be classified by application as: 1) pressure vessel; 2) structural; and 3) machine member.

For information and data concerning joints for pressure vessels such as boilers, reference should be made to standard sources such as the ASME Boiler Code. The following sections will cover only structural and machine-member riveted joints.

Basically there are two kinds of riveted joints, the lap-joint and the butt-joint. In the ordinary lap-joint, the plates overlap each other and are held together by one or more rows of rivets. In the butt-joint, the plates being joined are in the same plane and are joined by means of a cover plate or butt strap, which is riveted to both plates by one or more rows of rivets. The term single riveting means one row of rivets in a lap-joint or one row on each side of a butt-joint; double riveting means two rows of rivets in a lap-joint or two rows on
each side of the joint in butt riveting. Joints are also triple and quadruple riveted. Lap-joints may also be made with inside or outside cover plates.

Unified Screw Threads

American Standard for Unified Screw Threads

American Standard B1.1-1949 was the first American standard to cover those Unified
Thread Series agreed upon by the United Kingdom, Canada, and the United States to
obtain screw thread interchangeability among these three nations. These Unified threads
are now the basic American standard for fastening types of screw threads. In relation to
previous American practice, Unified threads have substantially the same thread form and
are mechanically interchangeable with the former American National threads of the same
diameter and pitch.

Standard Metric Keys & Keyways

Design of Standard Metric Keyways for Square and Rectangular Parallel Keys.

You may also refer detailed information on British Standard Metric Keys and Keyways

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Design of Keys

Design of Keys
Pulleys, gears, sprockets, levers, couplings and similar devices are employed to transmit torque to or from shafts and usually are rigidly attached to the shaft by shrink fits, setscrews, keys, splines or cotters. Shrink fits are suitable for permanent assemblies, setscrews for light service and cotters for axial loads. When the parts must be disassembled, keys or splines generally are used. A key is a machine member employed at the interface of a pair of mating male and female circular cross-sectioned members to prevent relative angular motion between these mating members. The key fits into mating grooves in the shaft and mating member called the keyway and transmit torque by shear across the key. The cutting of the keyway into the shaft reduces its strength and rigidity by an amount depending upon the shape and size of the keyway