Vacuum pump and linked-type thread groove spacer

A vacuum pump comprising:

• a casing in which an inlet port or an outlet port is formed, a stator component enclosed in the casing, a Siegbahn pump portion comprising a stator comprising a spiral groove having a first ridge portion, a second ridge portion and a root portion positioned between an outer side in a radial direction of the first ridge portion and inner side in the radial direction of the second ridge portion, and a thread-groove pump portion, wherein a linked-type thread groove spacer comprises the Siegbahn pump portion and the thread-groove pump portion and the linked-type thread groove spacer links the Siegbahn pump portion and the thread-groove pump portion;
• and a countersunk hole is provided in an exhaust channel surface of the root portion in the
• Siegbahn pump portion in the linked-type thread groove spacer, and the linked- type thread groove spacer and the casing or the stator component are fastened by a fixing bolt disposed in the countersunk hole wherein the countersunk hole is positioned closer to the outer side of the first ridge portion than the inner side of the second ridge portion.