NOTE: Fastener manufacturers use different terminology to  describe the parts of the blind rivet. The terms “mandrel,”  “spindle,” and “stem” are often used interchangeably. For  clarity, the word “stem” is used in this handbook and refers  to the piece that is inserted into the hollow sleeve. visual. A more detailed discussion on how to inspect riveted  joints can be found in the section, General Repair Practices.  Removal of friction-lock blind rivets consists of punching out  the friction-lock stem and then treating it like any other rivet. The self-plugging, mechanical-lock blind rivet was developed  to prevent the problem of losing the center stem due to  vibration. This rivet has a device on the puller or rivet head that locks the center stem into place when installed. Bulbed,  self-plugging, mechanically-locked blind rivets form a large,  blind head that provides higher strength in thin sheets when  installed. They may be used in applications where the blind  head is formed against a dimpled sheet.  Standard self-plugging blind rivets consist of a hollow sleeve  and a stem with increased diameter in the plug section.  The blind head is formed as the stem is pulled into the  sleeve. Friction-locked blind rivets have a multiple-piece  construction and rely on friction to lock the stem to the  sleeve. As the stem is drawn up into the rivet shank, the  stem portion upsets the shank on the blind side, forming a  plug in the hollow center of the rivet. The excess portion of  the stem breaks off at a groove due to the continued pulling  action of the rivet gun. Metals used for these rivets are 2117- T4 and 5056-F aluminum alloy. Monel$^{®}$ is used for special  applications. Many friction-locked blind rivet center stems fall out due to  vibration, which greatly reduces its shear strength. To combat  that problem, most friction-lock blind rivets are replaced by  the mechanical-lock, or stem-lock, type of blind fasteners.  However, some types, such as the Cherry SPR$^{®}$  3 ⁄ 32-inch  Self-Plugging Rivet, are ideal for securing nutplates located  in inaccessible and hard-to-reach areas where bucking or  squeezing of solid rivets is unacceptable.  [Figure 4-102] Manufacturers such as Cherry$^{®}$ Aerospace (CherryMAX$^{®}$,  CherryLOCK$^{®}$, Cherry SST$^{®}$) and Alcoa Fastening Systems  (Huck-Clinch$^{®}$, HuckMax$^{®}$, Unimatic$^{®}$) make many  variations of this of blind rivet. While similar in design, the  tooling for these rivets is often not interchangeable.  The CherryMAX$^{®}$ Bulbed blind rivet is one of the earlier  types of mechanical-lock blind rivets developed. Their main  advantage is the ability to replace a solid shank rivet size  for size. The CherryMAX$^{®}$ Bulbed blind rivet consists of  four parts: Friction-lock blind rivets are less expensive than mechanical- lock blind rivets and are sometimes used for nonstructural  applications. Inspection of friction-lock blind rivets is  It is called a bulbed fastener due to its large blind side  bearing surface, developed during the installation process.  These rivets are used in thin sheet applications and for use  in materials that may be damaged by other types of blind  rivets. This rivet features a safe-lock locking collar for more  reliable joint integrity. The rough end of the retained stem  in the center on the manufactured head must never be filed  smooth because it weakens the strength of the lockring, and  the center stem could fall out. CherryMAX$^{®}$ bulbed rivets are available in three head styles:  universal, 100° countersunk, and 100° reduced shear head  styles. Their lengths are measured in increments of  1 ⁄ 16 inch.  It is important to select a rivet with a length related to the  grip length of the metal being joined. This blind rivet can  be installed using either the Cherry$^{®}$ G750A or the newly  released Cherry$^{®}$ G800 hand riveters, or either the pneumatic- 4-48 Figure 4-101.  Friction-lock blind rivet. Mechanical-Lock Blind Rivets Friction-Locked Blind Rivets 4.  A rivet sleeve with recess in the head to receive the  locking collar.  3.  A separate, visible, and inspectable locking collar that  mechanically locks the stem to the rivet sleeve. 2.  A driving anvil to ensure a visible mechanical lock  with each fastener installation. 1.  A fully serrated stem with break notch, shear ring, and  integral grip adjustment cone.