Draft roller, spinning unit, and spinning machine

A draft roller suitable for drafting a fiber bundle, the draft roller comprising:

• a fiber contacting portion having a substantially uniform outer diameter, and
• a reduced-diameter portion provided at both ends of the fiber contacting portion, the reduced-diameter portion having an outer diameter smaller than the outer diameter of the fiber contacting portion to form a step of at least 1.5 mm by an outer peripheral surface of the fiber contacting portion and an outer peripheral surface of the reduced-diameter portion after abrasion of the outer peripheral surface of the fiber contacting portion;
• and
• wherein the outer diameter of the reduced-diameter portion is 25 mm, and the outer diameter of the fiber contacting portion before abrasion is 30 mm.

A spinning unit comprising:

• a draft device adapted to draft a fiber bundle, and includes a draft roller adapted to draft the fiber bundle by rotating, the draft roller including a fiber contacting portion having a substantially uniform diameter, a reduced-diameter portion having an outer diameter smaller than an outer diameter of the fiber contacting portion, and a step of 2.5 mm formed by an outer peripheral surface of the fiber contacting portion and an outer peripheral surface of the reduced-diameter portion;
• a spinning section adapted to spin the fiber bundle drafted by the draft device at a spinning speed of at least 400 m/min;
• and
• wherein the fiber contacting portion has a width in the axial direction of 18 mm and an outer diameter of 30 mm, and the reduced-diameter portion has an outer diameter of 25 mm.