Hole Callouts & Reference Dims

[Slacker22]

Hole Callout...
Square tube with a hole going through the entire part (both walls). The hole(s) are being located using a positional tolerance and basic dimensions. In this example, is best practice to call out the hole as one thru hole or two holes? We've always called this out as one hole thru but some are thinking because of the positional tolerance this should be called out as 2X.
Reference Question...
Here's an easy one. What is the best practice based on the most recent drafting standards for calling out a reference dimension?
REF
REF.
(xx)

 

[KENAT]

This is addressed in ASME Y14.5M-1994 section 5.11. Exactly how you do it is dependant on function, and the examples of your situation they look at actually use a composite positional tolerance to keep the 2 holes tightly coaxial while not as tightly constraining location on the part.

However, in none of their examples of coaxial holes do they use "2X".

Parentheses (xx) is the preffered method in 14.5-94 section 1.7.6. I doubt it changed in the latest version.

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[drawoh]

Slacker,

Do not be ambiguous. Provide a drawing view that clearly shows the hole going through both sides of the tube. This can be a section view, or an isometric view. Even hidden lines on your side view would do it. Show the centreline going all the way through.

SolidWorks labels holes THRU or THRU ALL, depending on how much stuff they go through, but I cannot find this in the standard. There is no substitute for a picture.

JHG

 

[ctopher]

In your examples, I would use "THRU ALL".
For a ref dim, I add parenthesis around the dim.
Not to be confused with dual dims, they use brackets.

Chris
SolidWorks 09 SP4.1
ctopher's home
SolidWorks Legion

 

[KENAT]

I would avoid using variations on Thru All etc as they aren't explicitly in the standard and I've seen them interpreted differently.

thread1103-257193

Is your question primarily relating to how to correctly apply the positional tolerance to 2 coaxial holes or is it more about making sure the machinist knows the hole goes through both sides of the tube?

I assumed the former as you mention position. To address the latter, making it clear graphically should be enough.

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[ctopher]

You can also use Projected Tolerance Zone.
A pic for us to see would help.

Chris
SolidWorks 09 SP4.1
ctopher's home
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[Slacker22]

The holes in question are the what I would call the "two" 10.5mm holes going thru both walls of the tube. See attachment. My experience has been these are denoted as 2X 10.5 THRU (OR THRU BOTH WALLS). I'm struggling with calling this 4X.
And what about the other "three" 12mm holes going thru both walls? If the 10.5's should be called out 4X then to be consistent would the "three" be called out as 6X even though they do not have any positional tolerance (GD&T) and are simply located via a plus/minus tolerance? That isn't making sense to me either.
Thanks for your help folks!
Your thoughts...

 

[KENAT]

In your case I'd stick with the 2X 10.5, don't say 4X. This matches both your former practice and what the std shows at the references I gave above. As Drawoh says use graphical methods to make it clear they go through both walls.

Minor point on your excerpt, the 15 dimension looks like it should also be basic, but you probably know that already.

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[PeterStock]

I would use 2X 10.5 THRU TWO WALLS. Assuming that A is the front or back surface of the tube and B is the top surface (both in the view shown), then the 15 should not be basic unless you add a C datum to the end.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[KENAT]

At the risk of breaking mine and the forums rule of going off topic, the reason I mentioned the 15 is because ASME Y14.5m-1994 5.2.1.1 "The location of each feature... is given by basic dimensions." and earlier in 5.2 "Basic dimension establish the true position from specified datum features and between interrelated features". I didn't bring up the datum labelling since it's just an extract and none of the datum identifiers are visible.

Of course if the hole(s) subsequently become the datum (or maybe some other datum structure that doesn't spring to mind) then indeed the 15 shouldn't be basic, hence the soft wording in my post.

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