CAB BODY REPAIR - CONTINUED
INSPECTION - CONTINUED
Rivet Failure. Signs of rivet failure include tipped heads, looseness, and chipped or cracked paint. If heads are tipped in
the same direction and rivets are loose in consecutive groups, the joint has undergone excessive load. Rivet heads that
are tipped in different directions and are not in groups may be improperly installed. With chipped or cracked paint, it
may be necessary to remove paint to check true condition of rivets. Rivets subjected to critical loads, but showing no
distortion, should be inspected if failure is suspected. The head should be drilled off, and the shank should be carefully
punched out. Failure is indicated by notched rivet shank and misaligned holes. Flush rivets showing head slippage
within the dimple or countersink indicate either sheet bearing or rivet shear failure and must be removed for inspection
and replacement. If failure of rivets cannot be detected by visual inspection, the joint can be checked by drilling and
punching out several rivets. If rivet shanks are notched, rivets should be replaced with next larger size rivets. If rivet
holes show elongation due to local failure in tearing of the sheet, next larger size rivet must be used in replacement. Any
deformation of the sheet around rivet, tear outs or cracks between rivets usually indicates partially failed or damaged
rivets. Complete repair of the joint will require replacement by the next larger size rivets. Use the next 1/32-in larger
diameter rivet to obtain a tight joint when original hole has been enlarged. If original size rivet is installed, rivet will not
be able to carry its share of shear load, and the joint will not meet its strength requirements.
Lock Bolt Failure. Lock bolts are used to withstand tension loads and high-shear loads. These fasteners are installed in
holes with an interference fit. No looseness can be permitted. Lock bolts showing evidence of being stretched, broken,
loose in holes or having heads that do not set flat against the surface must be replaced. Guidelines used in Rivet Failure,
above, for detecting rivet failures also apply to lock bolts.
When removing rivets, be careful not to enlarge rivet holes. This will require use of an oversize or larger
rivet for replacement.
Solid Rivet Removal.
File flat surface on manufactured head, if accessible. It is always preferable to work on manufactured head rather
than a head that is bucked over. Manufactured head will always be more symmetrical around shank.
Indent center of filed surface with center punch.
Use drill slightly smaller than diameter of rivet shank to avoid making rivet hole oversized.
Using drill slightly smaller than diameter of rivet shank, drill through rivet head.
Support back of rivet using sharp chisel. Cut rivet head along direction of rivet line or panel edge to prevent distor-
tion of panel and shear off weakened rivet head.
Support panel from opposite side and drive out shank with pin punch. If rivet is unduly tight because of swelling
between sheets, drill rivet shank out with undersize drill.
Blind Rivet Removal.
File small flat on rivet head.
Center punch flat. Support rivet backside, if possible.
Using small drill about the size of rivet pin, drill off tapered end of pin that forms lock.
Shear lock using pin punch to drive out pin.
Pry out remainder of locking collar.
Using drill slightly smaller than rivet shank, drill almost through rivet head.