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THE DISTRIBUTOR’S LINK
Anthony Di Maio
Anthony E. Di Maio attended Wentworth Institute and Northeastern University. In 1962 he
started working with Blind Fasteners as Vice-President of Engineering & Manufacturing for two
blind rivet manufacturers. He has been Chairman of the Technical Committee of the Industrial
Fasteners Institute (IFI) and is still involved in the writing of IFI specifications. In 1991, he
started ADM Engineering and is working with Fastener Manufacturers developing new fasteners
and special machinery. He can be reached at ADM Engineering, 6 Hermon Ave., Haverhill, MA
01832; phone and fax 978-521-0277; e-mail: tdimaio@verizon.net.
SECONDARY MANUFACTURING OPERATIONS
FOR BLIND RIVETS
There are secondary manufacturing operations that
must be performed to Structural blind rivets to make the
Structural blind rivet perform correctly.
Head
Point
MANDREL
STRUCTURAL SELF-PLUGGING PULL MANDREL
The Structural blind rivet has a long mandrel head.
The mandrel head also has a sealing ring around it’s
diameter. When setting the Structural blind rivet, such
as Monobolt or Interlock, the long mandrel head will
travel the complete length of the rivet body. There is
a large degree of friction when the long mandrel head
is being pulled the length of the rivet body. Because
of this high degree of friction the assembled Structural
blind rivet is submerged in a lubricant. This lubricant will
dry to the touch but will lubricate the mandrel head and
reduce the friction. Without this lubricant the friction of
the mandrel head traveling the length of the rivet body
is high enough that the mandrel could have a pre-mature
mandrel break before the structural rivet is set. This prematured
mandrel break will cause a mal-function and the
Structural rivet will not clamp the work pieces together.
Many steel mandrels of the Open-End series of blind
rivets are also manufactured with a phosphate coated
mandrels and these phosphate coating mandrels do
not get zinc plated. This phosphate coating to applied
CONTRIBUTOR ARTICLE
to prevent rusting. This phosphate coating can be
a secondary manufacturing operation at the plating
department. Many blind rivet manufacturers purchase
steel mandrel wire that is coated with phosphate. When
the mandrel making machine produces the mandrels
the phosphate becomes in contact with the tooling that
forms the point and head of the mandrel and deposits
phosphate on the point and head of the mandrels. This
phosphate prevents the steel mandrel from rusting.
Plating blind rivet mandrels:- The plating department
first clean the mandrels in the baskets of their automatic
plating production lines. The plating baskets are rotated
and have many holes for the plating chemicals to contact
the mandrels that are inside the plating baskets. The
holes in the plating baskets must be smaller than the
diameter of the mandrel. For example, the diameter
of the steel mandrel of a 3/32 diameter blind rivet is
.0565 +/-.001. The holes in the plating baskets must
be less then .053 diameter so that the 3/32 diameter
blind rivet mandrel that is .0565 +/-.001 will not enter
the holes. If the hole diameter is larger the mandrels will
enter the hole in the plating baskets and the mandrels
will bend from the weigh of the load of steel mandrels in
the turning plating baskets.
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