Blind rivets owe their popularity to ease of installation and versatility.Other tests such as blind head formation (usually in conjunction with break load test) and mandrel retention may be performed as required.Three major tests are used to ensure that rivets comply with the requirements of IFI 114, shear strength, tensile strength and mandrel break load.Most suppliers of quality blind rivets use this specification with a few variations. The most recognized standard is IFI 114 – Break Mandrel Rivets from the Industrial Fasteners Institute in the USA.There are no International standards covering the manufacture and supply of blind rivets.Make provision for drainage to allow water or other electrolyte material to escape.Build a barrier between the materials such as paint, plastic washers or gaskets.Avoid dissimilar metals by careful selection of rive shell material.When galvanic corrosion becomes a threat to the serviceability of the joint, the following suggestions may be worth considering.The following table illustrates which metals should and should not be used together.In applications high in moisture content – such as air conditioners and marine environments – particular care needs to be taken to minimize the effect of galvanic corrosion. Blind rivets are regularly used with dissimilar metals such as aluminum, stainless steel, mild steel, zinc-coated steel and copper.The rate of corrosion depends upon a) the difference in electrical potential, b) the conductivity of the electrolyte and c) the relative sizes of the contacting areas.When dissimilar metals come into contact in the presence of an electrolyte, a galvanic action occurs which corrodes one metal at a faster rate and the other more slowly.If the grip range is too large (rivet is too short), insufficient material may be left on the blind side to secure the joint.If the grip range is less than it should be (the rivet is too long), excessive material will be left on the blind side and more pulls will be required to break-off the mandrel. The amount of deformation in the shell during setting depends upon this grip range Blind rivets are designed to clamp together specific thicknesses of material.The integrity of the joint may be compromised. It is crucial that the mandrel not break at a load lower than the clamping force. Similar to a bolted joint, a blind rivet develops a clamping force to secure the joint members.Too little clamp force may fail to secure the joint. The break load is designed to prevent too much force being developed which may damage the material being fastened. The load required to break off the stem is governed by the amount of shell deformation required and a groove cut to a specific diameter just back from the end.Figure 5a-1 shows the stages of application. Withdrawing the stem is done with special tools operated by hand, pneumatics or electricity.A small portion of the stem remains trapped in the bottom of the shell to ensure the clamping force is retained in the joint.After the desired clamping force is achieved, the stem breaks off and is discarded.The rivet is 'set' by drawing the stem through the shell, which causes the shell to deform and clamp the material securely.Blind rivets are a two-part fastener consisting of a shell and a headed stem (mandrel) assembled so the shell can be placed into the work to be fastened.However, blind rivets are limited in their individual strength and should only be used when fastening relatively light gauge materials.Materials are permanently clamped and provided the correct rivet is used can withstand severe vibration and environmental conditions. The unit cost is also much lower than other types of fastener.īlind rivets are available in many types, sizes and materials to meet the requirements of the most demanding applications. Up to 15 rivets per minute can be installed without any specialized labor. There are three main reasons why blind rivets are used. Welding, sheet metal screws, bolts and nuts and solid rivets all require extensive labor. The use of rivets in fastening most applications has been proven to be superior and extremely cost effective when compared with other methods of fastening.Blind rivets are termed so because there is no need for access to the rear or 'blind' side of the joint. In these cases, the most common solution is to use Blind Rivets to fasten the job.There are many applications where the back of the job cannot be accesses, such as fastening to tubing or walls.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |