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THE DISTRIBUTOR’S LINK
LAURENCE CLAUS HOW FASTENERS ARE MADE - PART 1: COLD HEADING from page 10
In many cases a fastener made with one of these
three methods may employ many of the same or similar
subsequent manufacturing steps. Take for example a
socket head cap screw, the threading, heat treating, and
surface finishing may be similar or identical regardless
of the way the blank was formed. The only truly different
manufacturing method is the one employed to create
the blank. Depending on size, material, and quantity all
three of the above methods of manufacturing the blank
are viable, but only one may be best. Therefore, when
addressing this question of how a fastener is made, the
most significant differentiator is which of these three
processes was employed. Although we will touch on
many of the multiple steps to manufacture a fastener,
the primary focus of this series will be to explore these
three primary processes.
Although there are multiple factors that go into
the decision of which process to choose; part size
(diameter), order quantity, and material type are the
primary factors utilized to make a decision. Realistically,
most fasteners consumed in North America are produced
in large quantities in steel and between about #4 (M3)
diameter and ½” (M13) diameter. These are all factors
which favor cold heading, so that it is safe to assert that
of the three different processes, a fastener is most likely
going to be cold headed.
So, what is cold heading? Obviously the introduction
of the word “cold” suggests that temperature is involved.
In fact, that is a good observation although the word
itself may be a little misleading. In simple terms,
“cold” means that there is no specific and purposeful
introduction of heat. In other words, in cold heading
the raw material is introduced into the cold heading
machine at room temperature. In part 2 we will explore
warm and hot heading and see how the addition of heat
changes the formability equation and can be utilized
to manufacture parts that are large diameter or made
of difficult to form material. In Cold Heading, however,
we rely on the ability of the material to form without
additional heat input. In the heading process material is
moved and repositioned to create the desired geometric
form of the finished part. Although the finished shape,
especially on simpler parts, can often be achieved from
just the forming process, occasionally parts possess
complexities that necessitate secondary operations.
Parts that emerge from Cold Heading complete are
considered to be Net Shape (See Figure 1) and those
that may require additional processing to finish the
blank are considered Near Net Shape (See Figure 2). To
achieve these transformations, Cold Heading must follow
certain established “rules” about how much material
can be moved at any one time. Thus volume control is
an important limitation for cold heading manufacturers
and dictates what machines and how many times they
must actually strike the part to get to Net or Near Net
Shape. Since the process involves moving the material,
it produces no waste except for those parts that receive
a trim or piercing operation.
FIGURE 1: NET SHAPE EXAMPLE (LEFT IMAGE = NET SHAPE BLANK)
FIGURE 2: NEAR NET SHAPE EXAMPLE (UPPER IMAGE = NEAR NET
SHAPE BLANK, LOWER IMAGE = FINAL NET SHAPE)
CONTINUED ON PAGE 140