Fastening Archives - difference.minaprem.com http://www.difference.minaprem.com/tag/fastening/ Differences for Mechanical Engineering related topics Tue, 02 Jul 2019 07:50:15 +0000 en-US hourly 1 https://wordpress.org/?v=6.9.1 http://www.difference.minaprem.com/wp-content/uploads/2017/10/cropped-Minaprem.com-Fabicon-32x32.png Fastening Archives - difference.minaprem.com http://www.difference.minaprem.com/tag/fastening/ 32 32 Difference Between Thread Joint and Weld Joint http://www.difference.minaprem.com/joining/difference-between-thread-joint-and-weld-joint/ Tue, 02 Jul 2019 07:50:15 +0000 http://www.difference.minaprem.com/?p=1275 Joining can be performed either mechanically or chemically. A mechanical joint can be either temporary and permanent. A temporary joint is one that gives the provision of easy and quick dismantling of joined parts without rupturing them, whereas a permanent joint does not allow dismantling of assembled parts without breaking them. Weld joint and rivet joint are considered as permanent joints; while thread joint, cotter joint, knuckle joint, etc. are

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]]> Joining can be performed either mechanically or chemically. A mechanical joint can be either temporary and permanent. A temporary joint is one that gives the provision of easy and quick dismantling of joined parts without rupturing them, whereas a permanent joint does not allow dismantling of assembled parts without breaking them. Weld joint and rivet joint are considered as permanent joints; while thread joint, cotter joint, knuckle joint, etc. are temporary joints. Both types of joining have their relative pros and cons and both are indispensably required for assembly purposes for multifarious applications. In thread joining, components are assembled together by various threaded accessories such as nut, bolt and screws; and the same can be disassembled as and when required just by loosening the threaded accessories. Here the assembled components are tightly held together by the wedge action acting on the threads. However, thread joining requires drilled holes on the components for the passage of bolts or screws. Such series of holes can reduce the effective cross-sectional area of the components and also leads to stress concentration. Thus load carrying capacity of the assembled structure decreases considerably.

Welding is another mechanical joining process that requires application of either external pressure or heat in order to form a coalescence (weld bead) to permanently join two or more components together. Filler material, if required, can also be added. Welding is preferred for joining of two or more components having similar chemical composition; however, can also be joined dissimilar materials. There are several welding processes to effectively and economically join wide variety of materials in innumerable ways; each process offers several advantages over other. Unlike threading, it does not require any holes to be drilled on the components, but edges can be prepared for welding thicker components. If carried out properly with optimum set of parameters, welding can easily produce leak-proof joints. However, repair and replacement of welded structures are complicated and costly as it is one permanent joint. Moreover, many welding processes leave behind a heat affected zone (HAZ) surrounding the weld bead. This HAZ has different metallurgical properties compared to that of the base metal, and is usually susceptible to corrosion and cracking. Various similarities and differences between thread joint and weld joint are discussed below in the following sections.

Similarities between thread joint and weld joint

  • Both thread joint and weld joint come under mechanical joining domain as no chemical reaction takes place during joining.
  • Both can produce sound defect-free joint, if carried out properly.
  • Both the processes offer the feasibility to join more than two components in one step.

Differences between thread joint and weld joint

Thread Joint Weld Joint
Thread joint is one temporary joint. So the threaded assemblies can be dismantled easily without breaking the structures. Weld joint is one permanent joint, thus welded assemblies cannot be dismantled without rupturing the structures.
Thread joint requires pre-drilled holes on the parent components for the passage of bolt or screws. No such hole is required to drill on parent components for welding. However, edge preparation might be desired for welding thicker plates.
Due to presence of holes, effective cross-sectional area of the parent components reduces, and thus load carrying capacity of threaded assemblies reduces. Cross-sectional area of the parent component remains unaltered after welding (thus no drop in load carrying capacity after proper welding).
Thread joining gives an intermittent type joint as a finite pitch exists between two adjacent bolts or screws. Welding gives a continuous joint.
Bolt or screw head remains protruded on the surface, which hampers appearance and also restricts sliding motion on that surface. Reinforcement is the only protruded part in welding; however, it can be removed easily by grinding to improve appearance as well as to get a sliding surface.
Thread joint, particularly in presence of bolt, gets loose under incessant vibration. With the advancement in welding technology, now-a-days most weld joints remain stable under vibration.
Thread joint may not necessarily be leak proof. Thus it is not suitable for fluid-tight applications. If carried out properly, weld joints are usually leak proof.
Inspection, repair or replacement of threaded assembly is easier and cost efficient because it can be dismantled as and when required. Since welded assembly cannot be dismantled without destroying it, so repair or replacement is tough and costly.
Thread joint does not alter metallurgical and physical properties of the components. Most of the weld joints change physical and metallurgical properties of parent component, particularly surrounding the wend bead (in HAZ zone).
Thread joining does not lead to deflection of the structures, unless the components are very thin. Weld joining (mainly fusion welding processes) leads to palpable deflection due to volumetric shrinkage during solidification.

Difference between thread joint and weld joint

References

  • A Text-Book of Welding Technology by O. P. Khanna (Dhanpat Rai Publications).
  • Design of Machine Elements by V. B. Bhandari (Tata McGraw Hill Education Private Limited).

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]]> Difference Between Temporary Joining and Permanent Joining http://www.difference.minaprem.com/joining/difference-between-temporary-joining-and-permanent-joining/ Mon, 01 Jul 2019 10:30:10 +0000 http://www.difference.minaprem.com/?p=1264 In manufacturing industries, joining of two or more components is indispensably necessary for assembly purposes. Joining makes the production system more reliable, efficient and profitable. In fact, joining can be defined as one of the manufacturing processes by which two or more solid components can be assembled together with or without the application of external elements such as filler, strap, heat, pressure, etc. There exist various joining techniques in order

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]]> In manufacturing industries, joining of two or more components is indispensably necessary for assembly purposes. Joining makes the production system more reliable, efficient and profitable. In fact, joining can be defined as one of the manufacturing processes by which two or more solid components can be assembled together with or without the application of external elements such as filler, strap, heat, pressure, etc. There exist various joining techniques in order to assemble a larger variety of materials in innumerable ways. Some of these methods can join components permanently, while others can join temporarily. Accordingly, joining can be classified into two groups— temporary and permanent.

A permanent joint does not allow dismantling of joined parts without breaking them. As the name suggests, these joints are permanent in nature and usually offer a sound and leak-proof joining. Welding is the fast and foremost example for this category. Apart from welding, rivet joint, soldering, brazing, many adhesive bonding, etc. are also permanent joints. A temporary joint allows disassembly of assembled structures without rupturing the components. Easy disassembly makes inspection and maintenance very easy. However, strength of the temporary joints may not be as high as in a permanent joint. Various differences between temporary joints and permanent joints are given below in table form.

Difference between temporary joining and permanent joining

Differences between temporary joint and permanent joint

Temporary Joint Permanent Joint
Temporary joints allow easy dismantling of assembled components without breaking them. Permanent joints don’t allow dismantling of assembled components without rupturing them.
Temporary joints are not necessarily leak-proof. Permanent joints are usually leak-proof.
Strength of temporary joint is comparatively less. Strength of permanent joint is high. Usually joint strength is same with that of the components.
It facilitates fast, easy and cost efficient inspection. No destructive testing is required for inspection of joints. As permanent joints cannot be disassembled easily, so inspection is difficult and costly. Often destructive testing is carried out, which damages the assembled structures.
Repair and replacement are also easy. Repair and replacement are difficult and costly.
Temporary joints are suitable where frequent separation of assembled components is required. Permanent joints are suitable for such applications where separation is usually not desired in the service life.
Examples of various temporary joints:

  • Fasteners
  • Press fit
  • Cotter joints
  • Knuckle joints, etc.
 Examples of various permanent joints:

  • Welding
  • Brazing and soldering
  • Riveting
  • Adhesive joining (mostly)
  • Coupling, etc.

References

  • Introduction to Machine Design by V. B. Bhandari (McGraw Hill Education India Private Limited).
  • A Textbook of Machine Design by R. S. Khurmi and J. K. Gupta (S. Chand).
  • Theory of Machines by R. S. Khurmi and J. K. Gupta (S. Chand).

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