Englisg tap size question.

[Lstar]

.122/40 = ?/40

anyone please give me the answer.

[Jaz]

Machinery's Handbook shows 5-40 UNC as the closest match. (5-40 is actually .125-40)

[Lstar]

then what is .164-32 = ?-32

[Guest]

#8-32

 

For number sizes try this

 

# of tap x 13 + 60

 

8 * 13 + 60 = 164

 

quick little formula that gets you "in the ballpark" fairly quick

[Lstar]

Thanks jmparis.

 

8 * 13 + 60 = 164

 

can you explain what is 8 means , what is 13 and 60.

 

then how about .122-40 = ?-40

[Gary]

Just the american way lol

[Guest]

#8 is the number size of the tap in question but the 13 and the 60, nope never thought about that. Just a formula with a couple of numbers that help it all add up.

 

 

Is that .122-40 an exteranl thread?

 

.125 Ø is the major for a #5-40 but if it is an external thread many people cut them and the tolerance allows some below nominal size, this could be what it is.

 

If it is an internal thread, it would seem to be that it is either a #5-40 or a typo and it's supposed to be a #4-40 but there is enough of a question I would ask for clarification.

[Lstar]

It is a hole,it is internal thread

[Lstar]

Anyone out there please give me more explanation

[Guest]

Lstar,

 

Are you looking for an explaination of your thread size callout?

 

As I stated above, you should probably check for clarification on the thread size.

 

In all probability it is #5-40 but it is spec'd out wrong if that is the case. The customer should be able to clarify his needs.

[Lstar]

why you think that is 5-40, not 4-40?

 

how did you count it?

[Guest]

Dude, you need machinerys handbook.

 

Linky

 

The #4-40 thread is spec'd out as such

 

Internal 2B

 

Minor Ø .0939/.0849

Pitch Ø .0991/.0958

Major Ø .112

 

The #5-40 thread is spec'd out

Minor Ø .1062/.0979

Pitch Ø .1121/.1088

Major Ø .125

 

So as I stated above

 

quote:

---

If it is an internal thread, it would seem to be that it is either a #5-40 or a typo and it's supposed to be a #4-40 but there is enough of a question I would ask for clarification.

---

What ever the thread IS, .122 Ø major diamter is not a standard callout.

[jbel]

See here for thread diameter specs.

[Lstar]

thanks all of you.

[MattW]

John, your formula doesn't just get you "in the ballpark", it is right on. A little research reveals the following-

 

" In 1907 the American Society of Mechanical Engineers (ASME) defined two series that used Seller's thread, numbering the sizes by gage numbers from 0 to 30. In the series the major diameter increased by 0.013 inch with each size from 0 to 10, and by 0.026 inch between gages above #10."

 

(from http://www.sizes.com/tools/thread_history.htm )

 

And I had always thought the numbers were arbitrary. I find this kind of historical information interesting.

 

Anyway, I believe current ANSI recommendation is to specify standard screw threads by decimal size and TPI, e.g., .190-32 for #10-32 and .250-20 for 1/4-20. The number system will probably die at the same time as the universal adoption of the Metric system.

 

To address the original question, .122-40 looks like a misprint, and I would get clarification on what is desired.

 

MattW