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Thread Standard Variations

01/08/2012 10:13 AM

How many thread variations there the hell may be for a standard? For instance, I have believed, all UNEF 7/16 has 28 threads per inch. No! There turned to be also 7/16 - 25 UNEF, 7/16 - 32 UNEF, and so on ?!

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#1

Re: thread standard variations

01/08/2012 10:17 AM

There's lots. More than you can imagine.

Consult Machinery's Handbook.

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#2
In reply to #1

Re: thread standard variations

01/08/2012 10:55 AM

This is without getting into metric system, shape or pitch of thread...

http://en.wikipedia.org/wiki/Unified_Thread_Standard

http://en.wikipedia.org/wiki/Thread_pitch_gauge

See also

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#3
In reply to #2

Re: thread standard variations

01/08/2012 11:16 AM

It is clear there are UNC, UNF, UNEF, etc.with their distinctions from each other.

But, there turned to be

UNEF 7/16 - 25

UNEF 7/16 - 28

UNEF 7/16 - 32

particular variations of what I have been considering to be one - UNEF - standard ?!

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#4
In reply to #3

Re: thread standard variations

01/08/2012 11:30 AM

Doesn't it feel good to know the truth?

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#5
In reply to #3

Re: thread standard variations

01/08/2012 1:49 PM

Well you have the 3 classes, depending on application....I only see 28 for 7/16 UNEF

"A classification system exists for ease of manufacture and interchangeability of fabricated threaded items. Most (but certainly not all) threaded items are made to a classification standard called the Unified Screw Thread Standard Series. This system is analogous to the fits used with assembled parts.

Classes 1A, 2A, 3A apply to external threads; Classes 1B, 2B, 3B apply to internal threads.

Class 1 threads are loosely fitting threads intended for ease of assembly or use in a dirty environment.

Class 2 threads are the most common. They are designed to maximize strength considering typical machine shop capability and machine practice.

Class 3 threads are used for closer tolerances.

Thread class refers to the acceptable range of pitch diameter for any given thread. The pitch diameter is indicated as Dp in the figure shown above. There are several methods that are used to measure the pitch diameter. The most common method used in production is by way of a Go/no go gauge."

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#6
In reply to #5

Re: thread standard variations

01/08/2012 2:05 PM

Quote. I only see 28 for 7/16 UNEF

See, for instance:

DME Straight adapter N6-18

UNEF 7/16"-32

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#7
In reply to #6

Re: thread standard variations

01/08/2012 2:10 PM

Yeah but that's for a brass coupling, not a screw....That's plumbing, a whole nuther can O worms...lol

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#8

Re: Thread Standard Variations

01/08/2012 10:48 PM

Yuri, I'm not sure where your getting all of these pitches with "UNEF" designation. Typically there's only one "UNEF" designation per thread size. All other pitches are designated either "UN" or "UNS" (special). Your 7/16 thread UNEF pitch is -28. That's it, no other pitches with UNEF!

The 7/16-32 you mentioned is a "UN" designation, NOT a "UNEF" designation

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#9
In reply to #8

Re: Thread Standard Variations

01/09/2012 8:31 AM

Someone has ..in their ignorance... labelled the other thread pitches incorrectly,thus your confusion.
Terraman is correct the variants will be special or bastard threads.
bastard thread ( ′bastərd ′thred ) ( design engineering ) A screw thread that does not match any standard.

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#10

Re: Thread Standard Variations

01/09/2012 9:46 AM

Thank you guys !

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#11

Re: Thread Standard Variations

01/09/2012 7:31 PM

Whew! For a second when reading the title I thought it was referring to CR4 threads.

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Anonymous Poster (1); lyn (2); SolarEagle (3); TerraMan (1); woodygb (1); Yuri B. (3)

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