.086-56 UNC or 2-56 UNC 1

[bdbengtsson]

I had a previous customer that required tapped holes be called out with the decimal major diameter(.086)instead of the screw number (2). I haven't found an ASME specification that supports this. Does anyone know if there is such a specification?

 

[israelkk]

ASME B1.1-1989 Unified Inch Screw Threads, uses both.

 

[bdbengtsson]

Thanks for the quick response.

 

[KENAT]

ASME Y14.6-2001, Screw Thread Representation, in section 3.2, specifically 3.2.1.3, details how they should be called out on drawings.

"Numbered sizes may be shown because of established practices. The decimal equivalent, to three decimal places, should be shown in parentheses."

So you can show decimal without numbers, but if showing numbers you should show decimals too.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[bdbengtsson]

Thanks KENAT,
I attempted to look at ASME Y14.6 but our .pdf file is only accessible to the person/computer that downloaded it. As soon as I track down that "person" I'll look it up.

 

[NomLaser]

Gotta love 'smart' pdf's.

 

[fcsuper]

It's OK and common practice to only use the number, such as 2-58.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[KENAT]

It may be common practice but the relevant ASME standard does say you should add the decimal equivalent in parentheses. Many people ignore that, like they ignore that it says to explicitly reference ASME B1.1 or other thread form spec.

Do so at your own risk and don't blame me in the unlikely event someone uses it as an excuse to make you buy a non functioning piece of ****.

There was a thread on here not so long ago where someone was confused thinking the # was the diameter in inches or something like that. To me that makes the case for following the standard and making it clear.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[ewh]

I agree with KENAT - it may be common practice, but that doesn't make it correct per the standard. If your company standard defines it differently, then fine. If you default to the ASME standards, it is wrong.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[fcsuper]

We all know what "should" and "may" means in the ASME though.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[ctopher]

From my experience, use 2-56 UNC. The machinists understand this better. If you call out the decimal equiv, inspection may question tolerances.
Either way you choose that works for your company, be consistant and stay with one type.

Chris
SolidWorks 09, CATIA V5
ctopher's home
SolidWorks Legion

 

[ewh]

Inspection should not have any tolerance problem with a decimal equivalent in parenthesis, and any experienced machinist should be familiar with it. Otherwise, the problems actually run much deeper.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[ewh]

That should read "If otherwise, ..."

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[fcsuper]

Inspection is inspection. Many modern inspectors cannot properly read a drawing beyond simple notations. For some reason, "blueprint reading" doesn't seem to make it into the job skill requirements at many places.

I personally shy away from using decimal notation for threads, even as reference. However, as long as ASME Y14.100 is referenced on the drawing or even the thread standard itself, use of decimal or tradition numbers are both "allowed" and should be understandable to someone that can read "blueprints".

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[KENAT]

Allowed, but not preferred;-).

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484