ANSI has established three classes of fit.

More Questions from Threads, Fasteners and Springs

• A screw thread is a ridge of uniform section in the form of a helix on the external or internal surface of a cylinder.
• The axis of a screw is the longitudinal centerline through the screw.
• A Class 3 fit is exceptionally high quality and recommended only when high cost of precision is warranted.
• The root is the top surface joining the two sides of a thread.
• Thread length, finish, and proportions are some of the standard characteristics of bolts and nuts.
• Doubled threads are composed of two or more ridges running side by side.
• The form of a thread is the cross section of the thread cut by a plane containing the axis.
• Pitch is equal to 12 divided by the number of threads per inch.
• Multiple threads are composed of one ridge, and the lead is equal to the pitch.
• Rivets are not considered permanent fasteners.

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