STAKING BOLT
FIG9 is an enlarged cross-sectional view of the principal part showing the state in which an object to be fastened is fastened with a nut  FIG10 is a graph of the slip torque in the example 
FIG9 indicates a state in which an object 60 to be fastened is fastened by a nut 70 to the staking bolt of the present invention, which is caulked and fixed to the metal plate 30. The inner diameter of the nut 70, which is the inner diameter of the internal thread of the nut 70, is approximately equal to the root diameter of the external thread 12 formed on the shank 11. As mentioned above, when the outer diameter d1 of the non-threaded portion 22 of the shank 11 is smaller than the root diameter d2 of the external thread, as shown in FIG9, the nut 70 can be screwed in sufficiently deeply without interference with the external thread of the shank 11, and even when the object 60 to be fastened is thin, secure fastening can be implemented. Further, since the head 10 of the staking bolt of the present invention is also flat, reliable fastening can be implemented even when the total thickness of the metal plate 30 and the object 60 to be fastened is thinner than that in the prior art.  The staking bolt was inserted into the pilot hole having an inner diameter of 6.3 mm formed on a steel plate having a thickness of 1 mm, and was caulked and fixed using a die and a punch. Thereafter, when the slip torque was measured, as shown in the graph of FIG10, the average value of five bolts was 18 Nm.
cross-sectional view, graph
30
metal plate
12
external thread
11
shank
22
non-threaded portion
20
ring-shaped protrusion
10
head
70
nut
60
object
['1. A staking bolt comprising: a head; and a shank having an external thread, wherein a ring-shaped protrusion at an upper end of the shank and a ring groove located closer to the head relative to the ring-shaped protrusion are formed, wherein the head is flat and on a bearing face of the head, a whirl-stop protrusion having a plurality of radially extending arms protrudes with a thickness of t from the bearing face of the head, wherein a minimum diameter D between respective arms of the whirl-stop protrusion is larger than an outer diameter d of the ring-shaped protrusion, and wherein t x (D - d)/2 which is a longitudinal cross-sectional area A of a minimum diameter portion of the whirl-stop protrusion is equal to or greater than a longitudinal cross-sectional area of the ring groove.']