Correct Format for Thread Callout 9

[debodine]

I am new to this forum. I have performed a search of Eng-Tips but so far have not found an answer to my exact question as far as I have been able to locate. Please provide a link to the correct post if I overlooked it.

Right now my company does not have access to ANSI/ASME Y14.6 which I think would answer the question. I have submitted a request to the department head to purchase a copy, but I would prefer not to wait for the wheels to grind out a response.

Here is my specific question about the two schools of thought, using a typical thread callout. The difference is one group says also call out diameter of the hole to be drilled to prepare for tapping, second group says don't include diameter of the hole, the thread callout handles it all.

First school of thought:

.138-32 UNJC-3A
{diameter symbol] .1076-.1157

NOTE: We have these diameters published in our engineering design manual, but I have not been able to locate their source. I did not find them in AS8879, the replacement for MIL-S-8879, the former standard for UNJ thread callouts. AS8879 does not show a diameter callout but I still want to get input from ANSI/ASME Y14.6 if I can.

Second school of thought:

Same thing but do not call out diameter.

If someone could provide a quote (or a screen shot of the page) from ANSI/ASME Y14.6 that would be great and would serve me well to help update our drafting manual until the department head gets us our own legitimate copy of the standard.

Thanks in advance for your assistance.

 

[Belanger]

Jbeckhou -- I don't know if it's been mentioned above as to what standard your drawings are using (and there should indeed be a note imposing a standard) but the ASME standard Y14.5 clearly states in paragraph 1.4(e) that "the drawing should define a part without specifying manufacturing methods."

So engineering merely needs to tell the machinist what the finished part should look like. You say that if they choose the wrong drill and create bad parts that it is the engineers who get blamed? Perhaps they get the blame from those who don't know the governing rules, but the standard exonerates the engineers in that case.

Engineering really doesn't care how the part is made. What if I toss the part up in the air and shoot a hole through it with a gun? Hey, as long as the hole ends up meeting the drawing requirements, it's a good part.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

http://www.gdtseminars.com

 

[ewh]

JP, is that "gun drilling"?

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[drawoh]

jbeckhou,

How many holes have you drilled and tapped?

I figure I have done around thirty in my lifetime. That, probably, is more than many other people in this forum. Thirty tapped holes do not qualify me to argue with machinists. They are supposed to know what they are doing.

--
JHG