NON PERMANENT JOINTS

Héctor Alejandro Ramírez VillalpandoElvira Graciela Córdova Núñez

Nonpermanent Joints

The most common method of mechanical fastening is by using bolts, nuts, screws, rivets, pins, and a wide variety of other fasteners, these techniques are also known as mechanical assembly.

These assemblies may be structural (load-bearing) components and thus may be subjected to both shear and tensile stresses.

Nonpermanent

Screw

Snap

Shrink

Hole Preparation A hole in a solid body can be

produced by punching, drilling, chemical and electrical means, and high-energy beams, depending on the type of material, its properties, and its thickness.

Can be produced also during casting, forging, extrusion and powder metallurgy.

Hole has a tendency to reduce the component’s fatigue life.

Threaded Fasteners

Bolts

Screws

Nuts

Threaded Fasteners

If the joint is to be subjected to vibration, such as in aircraft and various types of engines and high-speed machinery, several specially designed nuts and lock washers are available. They increase the frictional resistance in the torsional direction, thus preventing vibrational loosening of the fasteners.

Types of Screws

Construction

Nuts

Washers

Rivets Most common

method: Riveting Used in the

construction and assembly of large commercials aircraft.

There are several types of rivets, and some may be solid or hollow.

Other Methods Of FasteningMetal Stitching or stapling

Is much like that of ordinary stapling of papers.

This operation is fast and particularly suitable for joining thin metallic and nonmetallic materials, and it does not require holes to be made in the components.

Seaming Seaming is based

on the simple principle of folding two thin pieces of material together.

For example: The lids of

beverage cans Containers for

food Household

products

Crimping Is a method of

joining without using fasteners.

Can be used on both tubular and flat parts.

Caps on glass bottles are attached by crimping.

Snap-In Fasteners Widely used in automotive bodies

and household appliances. They are economical and permit

easy and rapid component assembly. Particularly for plastic products.

Shrink and press fit Is based on the principle

of the differential thermal expansion and contraction of two components.

Typical applications include the assembly of die components and mounting gears and cam on shafts.

In press fitting, one component is forced over another, resulting in high joint strength.

Advantages

Ease of manufacturing Ease of assembly and transportation Ease of parts replacement, maintenance,

and repair Ease in creating designs that require

movable joints, such as hinges, sliding mechanisms for drawers and doors, and adjustable components and fixtures.

Lower overall cost of manufacturing the product.

Overview

Non-permanent joints: fasteners, screws, nuts Practical, quick, lots of options Disassemble-ability is important for

prototyping and learningPermanent joints: welding, rivets Hard to teach welding w/o equipment You can’t really take apart these

things without a lot of effort