Understanding Imperial Threads

[rocket100]

Hi Guys,

I have been working with Imperial for the first time as I have always been working with Metric. I have a drawing with the thread details of (.75-16 UNF - 2B .63MIN - FULL THD) This is a male thread and I didn't understand the full detail of this thread after several attempts in Google.

Now I am creating a female thread to the above spec but unsure what can it be? as I don't know the meaning apart from the UNF-2B Standard.

I would appreciate for your help to make myself understand or refer to some notes.

Thank you

regards

Rodney

 

[rocket100]

I apologies for the error. The dimensions given is for the female thread and I am trying to make a Male thread.

Thanks

 

[Jboggs]

Call out the same thing ".75-16 UNF - 2B". There is no difference between the callout for a male and a female thread. The dimensional tolerances for fit between male and female are built in to the callout.

 

[CorBlimeyLimey]

The .63MIN - FULL THD portion refers to the minimum length/depth of thread. That excludes any run-out or tapering created by the tapered lead-in of the tap.

 

[Mechomatic]

"There is no difference between the callout for a male and a female thread."

Basically true, but the fit designator "-2B" denotes a class 2 fit for an internal thread, whereas the matching external thread fit designator would be "-2A". To be fair, the thread fit designator is typically assumed to be class 2 and whether it's internal or external is also typically apparent from the drawing or application, so the fit designator is not strictly necessary unless you are calling for a class 1 or class 3 fit.

The dimensions indicate:

.75-16 UNF-2B .63 MIN- FULL THRD

In order, that's:

[.75" Major diameter of external threads]-[# of threads per inch, also called "thread pitch" or just "pitch] [callout for standard used to define the thread (UNC, UNF, etc)]-[fit class designator] [length of bolt/screw]-[length of thread]

So here you have a 3/4" diameter screw with 16 threads per inch, defined by the Unified National Fine thread standard, with a class 2 fit (class 1 is loose, class 2 is the most common, class 3 is very tight/precise) of internal threads (the "B" in the callout), with a minimum shank length of 0.63" and the entire length of the shank threaded (as opposed to some bolts you'll see that have a portion of the shank unthreaded).

 

[Screwman1]

Thread form dimensioning is all covered in the standards. The person machining the part will create it to fit the standard male and female dimensions. I can't quite understand why you are trying to model a thread form for a component, it just adds complexity without adding any information that is useful. People who make threaded parts will know exactly what do make if you just give them the information that you gave in the first post. Trying to actually make a solid model of a thread is very complex; we have people who specialize in just doing that for special threads and it is their primary job, so it isn't a trivial exercise.

 

[KENAT]

If in the US check out ASME B1.1.

Machinery's will also probably have enough to get you going.

Thread designation on drawings is often done poorly or even incorrectly and every now and then that can be a problem so I encourage you to learn how to do it properly.

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[rocket100]

Thank you guys really Appreciate for your answers.

Helped me a lot.

regards

Rodney

 

[jbeckhou]

See attachment.

Petrotrim Services, LLC

http://www.petrotrim.com

 

[jbeckhou]

It would help if I attached it!

Petrotrim Services, LLC

http://www.petrotrim.com

 

[KENAT]

rocket100, be a little careful with the document jbeckhou provides as some parts of it do not follow standard ASME Y14.5 practice if you care about such things.

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