Twist drills are complex metal cutting tools, with a cone-like internal structure. They have a few specific point geometries, such as planar, conical, cylindrical, ellipsoidal, or hyperboloidal. Twist drills also have two cutting edges, also known as lips. The lips are the edges formed by the intersection of flanks and faces. They are two in number with identical length and angle. Helix angle: Twist drills with a small helix angle (10°–19°) have a drawn-out helix. Twist drills with a large helix angle (27°–45°) have a compressed, short helix. Twist drills with a normal helix have a helix... Show more Twist drills are complex metal cutting tools, with a cone-like internal structure. They have a few specific point geometries, such as planar, conical, cylindrical, ellipsoidal, or hyperboloidal. Twist drills also have two cutting edges, also known as lips. The lips are the edges formed by the intersection of flanks and faces. They are two in number with identical length and angle. Helix angle: Twist drills with a small helix angle (10°–19°) have a drawn-out helix. Twist drills with a large helix angle (27°–45°) have a compressed, short helix. Twist drills with a normal helix have a helix angle of 19°–40°. Back taper: The diameter reduces slightly toward the shank end of the drill. This is known as “back taper”. Back taper provides clearance between the drill and work-piece preventing friction and heat. Lands: Lands are the cylindrically ground surfaces on the leading edges of the drill flutes. The width of the land is measured at right angles to the flute. Recess: Recess is the portion of the drill body between the flutes and the shank provided so as to facilitate the grinding of the body. Show less
Twist drills are complex metal cutting tools, with a cone-like internal structure. They have a few specific point geometries, such as planar, conical, cylindrical, ellipsoidal, or hyperboloidal.
Twist drills also have two cutting edges, also known as lips. The lips are the edges formed by the intersection of flanks and faces. They are two in number with identical length and angle.
Helix angle: Twist drills with a small helix angle (10°–19°) have a drawn-out helix. Twist drills with a large helix angle (27°–45°) have a compressed, short helix. Twist drills with a normal helix have a helix angle of 19°–40°. Back taper: The diameter reduces slightly toward the shank end of the drill. This is known as “back taper”. Back taper provides clearance between the drill and work-piece preventing friction and heat. Lands: Lands are the cylindrically ground surfaces on the leading edges of the drill flutes. The width of the land is measured at right angles to the flute. Recess: Recess is the portion of the drill body between the flutes and the shank provided so as to facilitate the grinding of the body.
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