What is the minor diameter for internal threads?
The major diameter of a thread is the diameter of the imaginary co-axial cylinder that just touches the crest of an external thread or the root of an internal thread. The minor diameter is the diameter of an imaginary cylinder that just touches the roots of an external thread and (or) the crests of an internal thread.
How can measure the minor diameter of internal thread?
The minor diameter of an internal thread is it’s inside diameter. The minor diameter of an external thread can be measured with GO and NOGO gages or directly with an optical comparator.
How do you inspect internal threads?
To inspect an internal thread, both ends of the thread plug are inserted into the threaded component. The Go end of the plug is supposed to thread in; the No-Go end is not. If this test checks out, the part can pass inspection.
How do you find the major and minor dia of a thread?
According to page 1528 of The Machinery’s Handbook (29th Ed.), that formula is given as A_S=(π/4)*((d_m+d_p)/2)^2 where the pitch diameter is d_p=d−0.649519×P, and the minor diameter is d_m=d−1.299038×P. I was trying to understand where the definitions of d_p and d_m come from.
What is meant by minor diameter?
Minor Diameter: The smallest diameter of the thread of the screw or nut. The term “minor diameter” replaces the term “core diameter” as applied to the thread of a screw and also the term “inside diameter” as applied to the thread of a nut.
What is the measure of internal thread?
Method: Measuring the axial distance between the edge of the threaded Measuring the axial distance between the edge of the threaded bore and the center point of the bottom of the first thread tooth.
How do you inspect screw threads?
Cutting accurate threads often means measuring the cutting tool as well as the completed thread. A convenient and common means of checking the threads of critical parts is to use a simple thread gage, a profile piece that measures the thread form accuracy, the profile in axial plane of one pitch.
What is the major and minor diameter of threads?
Major Diameter is the largest diameter of a screw thread. Whereas, Minor Diameter is the smallest diameter of a screw thread.
What are the dimensions of the minor diameter of a thread?
The actual dimensions of the minor diameter for any particular thread size can be approximated at 80% of the major diameter for the purposes of conventional representation. Fig. 17.12. Drawing convention for a male thread.
What is the most important rule in part thread inspection?
One of the most important rules in part thread inspection is to insure that the part threads are clean, free of burrs and other obstructions. Incomplete threads or threads with poor form or surface finish will also cause problems and adversely affect the function of the gage and the inspection of the threaded part.
What does it mean when the internal part thread is undersized?
Many times this means that the internal part thread is undersize at the pitch diameter or at the major diameter. It may also indicate a problem with the thread form or the lead of the thread. When this happens, a review of the thread cutting or forming tool geometry should occur.
What are the pass/fail inspection methods for threading?
One of the basic pass/fail inspection methods is to use Fixed Limit Go / No-Go gages. Go / No-Go gages include working thread plug gages for inspecting internal part threads and thread ring gages for inspecting external part threads. The most important tip to remember is: never force a gage into the part.