A fastener is a hardware device that is used for creating non-permanent joints.Fasteners can be used to close a container of a box or an envelope, or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container, etc.
Other alternative methods of joining processes for joining materials include welding, soldering, brazing, crimping, taping, cementing, gluing or the use of other adhesives. The use of forces such as magnetic force or even frictional force can also join materials. Stainless steel, carbon steel, and alloy steel are the three major steel fasteners manufactured in industries fasteners. With the help of below charts you can identify almost any type of Bolt and Screw different types of Fasteners, Head styles in Fasteners, Drive types in Fasteners, Washer types in Fasteners and Nut types in Fasteners.
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Screw thread is a continuous helical groove of specified cross-section produced on the external or internal surface. A screw thread formed on a cylinder is known as straight or parallel screw thread, while screw thread formed on a cone or frustum is known as the tapered screw thread Axis of a thread: This is an imaginary line running longitudinally through the center of the screw. Crest: Crest of the thread is the top most surface joining the two sides. Root: Root of the thread is the bottom of the groove between the two flanks. Flank: Flank of thread are straight edges which connect the crest with the root of the thread. Pitch: Pitch of a thread is the distance measured parallel to the axis from a point on a thread to the corresponding points on adjacent thread forms in the same axial plane and on the same side of the axis. Depth of thread: Depth of a thread is the distance between the crest and root of the thread. Major diameter: It is an imaginary largest diameter of the thread which would touch the crests of an internal or external thread. Minor diameter: It is an imaginary smallest diameter of the thread which would touch the roots of an external thread. Pitch diameter: It is a theoretical diameter between the major and minor diameter of screw threads. Helix angle: On the straight thread, It is the angle made by the helix of the thread at the pitch line with the axis.Lead angle: On the straight thread, It is the angle made by the helix of the thread at the pitch line with a plane perpendicular to the axis. Lead angle is measured in an axial plane.
Flank angle: Flank angle is the angle made by the flank of a thread with the perpendicular to the axis of a thread. Included angle: Included angle is the angle between the flanks or slope of the thread measured in an axial plane. The lead: It is the distance the nut moves parallel to the screw axis when the nut is given one turn. For a single thread as shown in the figure above, the lead is the same as the pitch of the screw thread. The following are the important dimensions and geometries concerned with toothed gear: Pitch Circle :Pitch circle is the apparent circle that two gears can be taken like smooth cylinders rolling without friction. Addendum Circle :Addendum circle is the outer most profile circle of a gear. Addendum is the radial distance between the pitch circle and the addendum circle. Dedendum Circle :Dedendum circle is the inner most profile circle. Dedendum is the radial distance between the pitch circle and the dedendum circle. Clearance :Clearance is the radial distance from top of the tooth to the bottom of the tooth space in the mating gear. Backlash :Backlash is the tangential space between teeth of mating gears at pitch circles. Full Depth :Full depth is sum of the addendum and the dedendum. Face Width :Face width is length of tooth parallel to axes. Diametral Pitch :Diametral pitch (p) is the number of teeth per unit volume. p = (Number of Teeth) / (Diameter of Pitch circle) Module : Module (m) is the inverse of diametral pitch. m = 1/p Circular Pitch :Circular pitch is the space in pitch circle used by each teeth. Gear Ratio :Gear ratio is numbers of teeth of larger gear to smaller gear. Pressure Line :Pressure line is the common normal at the point of contact of mating gears along which the driving tooth exerts force on the driven tooth. Pressure Angle :Pressure angle is the angle between the pressure line and common tangent to pitch circles. It is also called angle of obliquity. high pressure angle requires wider base and stronger teeth. Pitch Angle :Pitch angle is the angle captured by a tooth.
Pitch angle = 360/T Contact Ratio :Contact ratio is angle of angle of action and pitch angle. Path of Approach :Path of approach is the distance along the pressure line traveled by the contact point from the point of engagement to the pitch point. Path of Recess :Path of recess is the distance traveled along the pressure line by the contact point from the pitch point to the path of disengagement. Path of Contact :Patch of contact is the sum of path of approach and path of recess. Arc of Approach :Arc of approach is the distance traveled by a point on either pitch circle of the two wheels from the point of engagement to the pitch. Arc of Recess :Arc of recess is the distance traveled by a point on either pitch circle of the two wheels from the point to the point of disengagement. Arc of Contact :Arc of contact is the distance traveled by a point on either pitch circle of the two wheels during the period of contact of a pair of teeth. Angle of Action :Angle of action is the angle turned by a gear during arc of contact. Classification of gears can be done according to the relative position of the axes of revolution into three types. They are:
A key is a machine element fitted in an axial direction into the mating member, such as pulleys, gears. The primary function of the key is to prevent the relative rotation between the shaft and mating member. In most of the applications, the secondary function of the keys is to prevent the relative rotation between the shaft and mating member. In most of the applications, the secondary function of the keys is to prevent relative movements in the axial direction of the shaft.
The cutting of key-ways reduces the strength and rigidity of the shaft. Sometimes, setscrews are used to seat the key firmly in the key-way and to prevent axial movement of the parts. The following are the five common types of keys: 1. Square key: A square key is sunk half in the shaft and half in the hub of a gear, pulley or crank. In general, a square key has its sides equal to one-fourth of the shaft diameter. 2. Rectangular Key: Rectangular or flat keys are used where the weakening of the shaft is serious and where added stability of the connection is desired, as in machine tools. Flat keys with uniform cross-section are called feather keys, otherwise, a taper of 1:100 is provided on the thickness while the width is kept uniform. Feather key permits axial movement of the hub on the shaft. Tapered keys are often provided with gib head which facilities their removal, when the other end is inaccessible but gib-head, is dangerous for workmen. 3. Saddle key: Saddle keys fit in the key-way of the hub only; there is no key-way on the shaft. Saddle keys are suitable for light service or in cases where relative motion between shaft and hub is required for adjustment and the key way cannot be provided on the shaft. The power is transmitted by friction between that inner hollow cylindrical face of the key and shaft. Sometimes, flat saddle keys are used in which the inner surface of the key is left flat and the shaft is planed off to accommodate the key. 4. Woodruff key: A woodruff key is an adjustable sunk key in the form of an almost semi-circular disk of uniform thickness. The key requires a circular type of key-way in the shaft. It can be used with the tapered shaft because it aligns itself in the seat. The larger depth of key-way prevents the tendency of the key to slip over the shaft, but it weakens the shaft more than that by the use of straight keys. 5. Tangent Key: Tangent keys are made in two parts, each tapered to ensure a tight fit. The face of the tangent keys is kept inclined |
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