Dimensioning to hidden lines

[KENAT]

The question of whether to dimension to hidden lines came up a few weeks back and I think the reference given was slightly wrong.

ASME Y14.5M-1994 paragraph 1.4g (not 1.4c)

... Dimensions should be shown in true profile views and refer to visible outlines. [\quote]

My checker and I were looking for it this morning.

 

[KENAT]

The question of whether to dimension to hidden lines came up a few weeks back and I think the reference given was slightly wrong.

ASME Y14.5M-1994 paragraph 1.4g (not 1.4c)

... Dimensions should be shown in true profile views and refer to visible outlines.

My checker and I were looking for it this morning.

(sorry user error)

 

[ewh]

ASME Y14.5 para 1.4(g)

 

[ewh]

If the original post refered to para 1.4(c), then you are correct, it was a typo.

 

[KENAT]

ewh, it wasn't a dig. Your original post pointed us in the right direction, just thought I'd post the paragraph in case anyone was looking.

My checker just got a drawing from another division of the company to look at which leaves a little to be desired, this is just one of the issues. Being from another division he was being extra cautious and making sure he could back up any changes from the standard.

 

[ewh]

No problem! This is a prime example of why we should use this forum as a resource, but not as a final authority.

 

[Tunalover]

A pretty fundamental rule: don't dimension to hidden lines.

Tunalover

 

[drawoh]

KENAT,

The standard says "should" as opposed to "shall". Sometimes, I hate adding a section view to an otherwise, simple, easily read drawing.

Okay, I am being pedantic.

JHG

 

[KENAT]

Hey, I'm just quoting the standard, I'm making no judgment.

OK that’s a lie I do have an opinion but it’s my opinion not a rule, unless one day they’re dumb enough to make me a checker……

You bring up an interesting point on the should/shall. My checker occasionally moans that when the standard changed from mil spec to the ASME that it got watered down and a lot of the shalls got replaced by shoulds. I wonder if this is a case in point.

I frequently add sections for just one or two dimensions. To me it’s usually clearer, and using 3D cad to generate the drawings hardly takes longer, than dimensioning to a hidden line. However, I’m sure it confuses some of the people who don’t really know how to read a drawing.

 

[pdybeck]

I like creating a broken-out section in the view you are trying to dimension a hidden line. This creates a non-hidden line in that view, without having to create another view just to show a dimension to 1 would be hidden line.

 

[drawoh]

pdybeck,

A broken out section is easy to do on a drafting board, and hard to do in 3D CAD like SolidWorks.

My understanding is that "should" and "shall" are used deliberately in standards, with a precise grammatical meaning.

Dimensions to hidden views are bad practise, and should be avoided. Sometimes, avoiding them is a lot of work, and it does not accomplish much. Your primary objective is to provide clear, unambiguous information, and on simple stuff, a dimension to a single, clear hidden line is clear and unambiguous.

JHG

 

[ewh]

The problem with allowing these exceptions is that they will then multiply. Where do you draw the line? If I were checking the drawing of someone with little drafting experience, I would be very strict about violations of this type. If it where a more complicated drawing done by someone with good experience and habits overall, I would tend to follow the "should" road and let it slide.

Something I was told when I was just starting out - "A good drafter (designer, etc) doesn't blame his tools."

 

[KENAT]

We're in a situation where most of the people preparing drawings have little if any drafting training (and no real checking) and have just been doing it their own way for years, with the results you'd expect.

Hence we're tending to be fairly strict, like ewh says.

drawoh you’re right about should and shall usually having defined meanings, my point was just what I said. Essentially perhaps it used to be shall and got watered down to make it more palatable. Pure conjecture and at the end of the day if the spec says should then it means is should be done unless there is a really good reason not to.

Also our 3D CAD supports broken out sections, though it does take very slightly more effort than just a plain section.

 

[pdybeck]

drawoh,

What do you mean by a broken out section is hard to do in SolidWorks? I do it all the time - it takes a few extra seconds. Maybe I am missing something?? Could you explain?

 

[drawoh]

pdybeck,

Are we talking partial section views, or a section view built into an otherwise, standard view?

Partial section views in SolidWorks are easy. Actually, there is a way to add a section break into a standard view, but it is extra work, and I am talking about absolutely simple stuff where you just want to get the drawing done and get onto the next task.

The primary standard has to be clarity.

JHG

 

[pdybeck]

drawoh,

I am talking about a broken-out section view.

Per SolidWorks help file ... "broken-out section is part of an existing drawing view, not a separate view. A closed profile, usually a spline, defines the broken-out section. Material is removed to a specified depth to expose inner details. Specify the depth by setting a number or by selecting an edge in a related view."

I just draw a closed spline around the area I am interested in, select the spline, and then click on broken-out section view (you may have to add this button to a toolbar). Then you can set the depth of the broken out section. I find it easy to just pick an edge or face that I want the cut to extrude down to (picking this in another view is sometimes easiest). This method is pretty quick for me. Only takes about 10 seconds to add this type of view. Look at the SolidWorks help file under "broken-out section".

 

[CheckerRon]

REGARDING SHALL vs SHOULD:
Mil Standard documents often used the contracturally binding terms "shall" and "will" when setting standards and practices. I loved it! It eliminated all arguements. ANSI/ASME industry standards are controlled by contankerous committees that rarely make hard rules on anything. Thus the wimpy "should" or "preferably" when "Shall" is truly appropriate.
My pet peeve (as one who designs with GD&T) is Paragraph 2.1.1.1 "Positional Tolerancing Method" of ASME Y14.5M-1994. It starts out "Preferably, tolerances on dimensions that locate features of size are specified by the positional tolerancing method described in Section 5."

 

[Heckler]

CheckerRon - It's to bad that most if not all Mil Specs will be controlled by commercial companies and all future releases will be driven by words like "Preferably" and "advantageously" verses "shall" and "will"

Best Regards,

Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)

Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

 

[ctopher]

All Mil stds will preferably, advantageously and shall be controlled by commercial companies, eventually.

Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[ringman]

CheckerRon,

Would you use positional tolerancing to locate a pattern of rivets or a pattern of holes which were to be match drilled for rivets in a subsequent assembly?