Standard Hole Feature Tolerances

[kevcha]

Hi,
I was wondering if anybody could help me with a query. A number of years ago I worked within the aerospace manufacturing industry and remember that our drawings had a spec/standard in the title block that when reviewed told you general tolerances for linear dimensions and hole features (drilled holes, tapped holes, rivet holes etc) this was used if a tolerance was not specified on the actual drawing. Problem I have is that a customer is using ASME Y14.5 and is using trailing digits to specify a tolerance. Problem with this is that when drawings have been updated to CAD drawings a simple 3/8" thread depth now becomes 0.375" is subject to 3 decimal places tolerance which is +/-0.005". Is there something within ASME that does what I can remember from aerospace?

Thanks

 

[KENAT]

Not that I'm familiar with - and any such spec like ISO 2768 would have to be invoked some how for it to take effect.

If your customers don't reference some other spec and just have the typical "unless other wise stated .xxx = +-.005" block tolerance then that is what applies.

When they updated the drawing they should probably have directly toleranced such features to ".375 +-.030" or whatever was implied by fractional values on old drawing.

Posting guidelines faq731-376

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

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[drawoh]

kevcha,

If the thread depth is specified as .375", and the titleblock tolerance is [&pn;].005", then the tolerance is [±].005". You can always call and ask if they really mean it!

The problem with both English and metric drawings is that lazy drafters do not review all the dimensions for tolerances.

--
JHG

 

[CheckerHater]

Will it ruin your part if you round dim up to .38?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[dgallup]

I have seen a lot of companies (allegedly using ASTM Y14.5) put different default tolerance on their drawings for fractional and decimal dimensions. Then they leave dimensions like your 3/8" as fractions if they don't want the default 3 decimal place tolerance to apply. If you need to make everything decimal then I think you need to add tolerances to this dimension. I find it really sloppy to overly rely on default tolerances, I've seen drawings where every dimension is nominal. Did anybody take any time to think about what the individual tolerances need to be?

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[ctopher]

If you leave it as a fraction as 3/8, what is your tolerance? Is it still the same as the decimal tolerance?

Chris, CSWA
SolidWorks '15
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SolidWorks Legion

 

[dgallup]

As I've said, the drawing title block will call out different default tolerance for fractions, say 0.030" and 1, 2 & 3 decimal place numbers, say 0.030, 0.010 and 0.005 respectively.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.