Register to reply

Difference between nominal and major diameter in threads

by hihiip201
Tags: diameter, difference, major, nominal, threads
Share this thread:
hihiip201
#1
Feb26-13, 08:54 PM
P: 163
Hi guys:


I am having trouble with differentiating nominal and major diameter, from what I get on google as well as my textbook, the nominal diameter is the largest diameter in the thread and major diameter is the distance between crest to crest. but aren't the two the same?




thanks
Phys.Org News Partner Science news on Phys.org
Scientists develop 'electronic nose' for rapid detection of C. diff infection
Why plants in the office make us more productive
Tesla Motors dealing as states play factory poker
Travis_King
#2
Feb27-13, 10:24 AM
P: 841
Nominal diameter is the diameter from crest to crest that the fastener is listed as. i.e. a 1/8" bolt has a nominal diameter of .125 inches. However, if you measured the outside diameter of the fastener from crest to crest you would find it slighly different (positive or negative depending on the material, grade, purpose, etc.) depending on the manufactured tolerances. The Major Diameter measures the distance between external crests for male threads and internal roots for female threads, and describes an actually measured dimension, rather than a theoretical, design dimension.
hihiip201
#3
Feb27-13, 06:58 PM
P: 163
Quote Quote by Travis_King View Post
Nominal diameter is the diameter from crest to crest that the fastener is listed as. i.e. a 1/8" bolt has a nominal diameter of .125 inches. However, if you measured the outside diameter of the fastener from crest to crest you would find it slighly different (positive or negative depending on the material, grade, purpose, etc.) depending on the manufactured tolerances. The Major Diameter measures the distance between external crests for male threads and internal roots for female threads, and describes an actually measured dimension, rather than a theoretical, design dimension.

so if tolerance is zero (in theory), the major and nominal should be the same?

Travis_King
#4
Feb28-13, 10:07 AM
P: 841
Difference between nominal and major diameter in threads

From what I understand, the Nominal diameter is the diameter of the cylindrical piece that they cut the threads from. So if they were able to cut the threads so that the crest-to-crest diameter was the same as the original cylinder, then yea. But Nominal means it's what they are calling it. A .5" bolt may have no points on it which measure .5", it's the way they label them.
hihiip201
#5
Feb28-13, 11:05 AM
P: 163
Quote Quote by Travis_King View Post
From what I understand, the Nominal diameter is the diameter of the cylindrical piece that they cut the threads from. So if they were able to cut the threads so that the crest-to-crest diameter was the same as the original cylinder, then yea. But Nominal means it's what they are calling it. A .5" bolt may have no points on it which measure .5", it's the way they label them.

ya I remember what I learned from technical drawing class is that, nominal is just what you will order at home depot...


Register to reply

Related Discussions
Difference between major, minor and specialist program Academic Guidance 4
Nominal Primary Diameter Chemistry 0
Finding fluid flow rate in a pipe, given pressure difference, length, and diameter Engineering, Comp Sci, & Technology Homework 2
Nominal Pipe Size and Diametre Nominal General Engineering 13
Ode and pde-the major difference Differential Equations 6