Unilateral Profile Tolerance over a Limited Area.

[RLD89]

Please advise.

The attachment shows three callouts of a surface profile.
The top picture is simple enough. A bi-lateral tolerance with the limited length is called out with a center line (one small lines between longer lines, reference Figure 1.1 of 1994).
The middle picture depicts a Unilateral tolerance over a limited length. The unilateral tolerance over a limited length is called out with a phantom line (two smaller lines between 2 longer lines, reference Figure 6-18 of 1994). Technically, without the “single dash” the length is not called out correctly.
The bottom picture alternative to the Limited length unilateral tolerance. It uses both types of lines on opposite sides of the surface to be control. This is the only way to represent both types of lines and meet the requirements of the 1994 spec.

Perhaps either the mid or lower options will achieve the desired result. To make the drawing as clear as possible I will choose lower picture and show on a blown up detail view to make the intent clear. A flag note could be added to clarify? Any suggestions for improvement?
Thanks,

 

[CheckerHater]

In my opinion, mixing chain- and phantom-lines in close proximity will be confusing.

Would you consider using "between" symbol?

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

 

[RLD89]

Yes, that is a good idea, easily done. Thank you.

 

[mkcski]

In addition to the between symbol (double ended arrow), I would recommend using the unequally disposed "U" symbol per per 8.3.1.2. This would control the position of the tolerance zone relative to the BASIC profile without the confusing "special" lines.

Certified Sr. GD&T Professional

 

[CheckerHater]

@mkcski: OP was specific about working per 1994 standard.

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

 

[mkcski]

Thanks for the insight, which I totally missed. Shame he cannot update to 2009 and take advantage of better symbology.

Certified Sr. GD&T Professional

 

[RLD89]

I have tried, but management is not ready. I can put this in my reasons to make the switch folder.
Regards,

 

[ewh]

Before 2009 came out, I managed to sneak in the symbol citing Y14.41 (which we were also referencing at the time).

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

 

[mkcski]

RLD89:

Regarding moving to 2009 release from 1994: be aware, the latest DRAFT of the next release of Y14.5 was published in Feb 2016. I have not looked for and am not aware of newer DRAFTS, so I assume the next release is forthcoming in the "near" future - the Committee is voluntary and operates at a slower pace - meaning maybe sometime next few years - surprise us. You might want to wait so you can skip over 2009 to the latest. But like software, skipping versions is not recommended practice.



Certified Sr. GD&T Professional

 

[RLD89]

This is really god conversation. The problem is our company as a whole lacks adequate GD&T knowledge. We have adapted 1994, used it poorly and paid the price. 7 of 10 know nothing of any standard. Less than 1 in 10 understand how to use it correctly. If the company were to have comprehensive training, I would prefer take the leap to the latest version. I have presented a number of training options, but extensive training is not going to happen for at least another couple of years. Changing the culture difficult. Absurd as all that is to the users of this forum, this is reality.

 

[mkcski]

RLD89:

Thanks for the insight into you dilemma. Selling GDT is really difficult. I have taken several approaches to "convincing" others to institute it - not all were successful. Almost all are based on what can happen when GDT is "missing" from the drawings. Many books (Alex Krulikowski and Jim Meadows come to mind) have an introductory chapter on the benefits of GDT.

To me, it is a philosophy - a thinking tool. Using the pillars of GDT - datums, size, form, orientation and location - you can show how "thinking" about these at the design stage saves BIG dollars during mfg and inspection because the design intent is communicated to the organization...make it like this and it will function as intended.

Also, the use of institutional (tribal) knowledge to communicate product definition is greatly minimized because part function and fit-up are "captured" on the drawing in the symbols. This is especially critical with outsourcing of parts to build to print shops.

Certified Sr. GD&T Professional

 

[RLD89]

Indeed to all you said. I have both those books. I have done many tolerance stack ups to identify and correct problems created by poor drawing definition. I have made all the pitches and cited many specific examples, but the bottom line is we are too busy to implement training. I now review drawings to prevent the bad things from happening, but it will never be as good as well trained users. I will continue every day to make the pitch and really appreciate the comments.
Regards to all.

 

[3DDave]

Unless your company gets $500,000+ in a pile of parts that don't fit, I would suggest not mentioning D&T to anyone anymore.

People who aren't suffering from a problem don't like to be told they have one. Until there is a company-threatening level of problems, they won't be suffering and will think their only problem is being told what to do when they don't see any problem.

It's clear they aren't open minded or proactive.

If there is a problem, be prepared for the company to hire an 'expert' who interviews well, but knows little, to be brought in to 'fix' the process. Management will do so to refuse to admit you were right. This person's job will depend on being more 'right' than you are, so they will be looking to find any fault as proof and use that proof with management as a reason to eliminate your job. This can happen because management is incapable or simply disinterested in how the work is done and operates on the good-buddy system.

tl;dr If you are committed to developing a job skill for a company that has no use for that skill, find a new company.

 

[mkcski]

3DDave

Well said!

Certified Sr. GD&T Professional