hexagon dimensioning with GD&T 3

[rupeshpahwa]

I have this old Drawing.Is this the best way to dimension a hexagon using Gd&T .

 

[drawoh]

rupeshpahwa,

It is not horribly wrong, but it is not the way I would do it.

For starters, the dimension across the corners is wrong. This is controlled by the width across the flats. The number applies across the sharp corners, which almost certainly, will be filed down a bit, rendering your very accurate tolerance hopeless. You can apply a reference dimension. You can provide a detail to show how the corners are to be finished, with a resulting real dimension and tolerance.

It would be legal, however silly, to leave off the across flats dimensions, and apply a basic dimension across the corners to the theoretical points. You would have to apply a profile tolerance to the outline.

You need only one reference to the across flats dimension. Apply a 3X to it, and the positional tolerance. I would add a reference to datum_B to whatever feature control frame you use. Your tolerances are very accurate. I do not know your requirements, but this is way more accurate than you need for wrenching.

Consider using a profile tolerance to control your hexagonal shape.

JHG

 

[pmarc]

rupeshpahwa,
Please take a look at following link:

http://tec-ease.com/gdt-tips-view.php?q=153

This might also help you to deal with the hexagonal feature. My additional remarks to this example would be that according to ASME Y14.5-2009 standard, the abbrevation for equally spaced feature should be EQLSP instead of EQSP, and the term BOUNDARY is optional, so it does not have to be there. If you have an access to Y14.5M-2009 standard you can take a look at fig. 8-24 to see how the combination of profile and position tolerances should properly look like.

 

[rupeshpahwa]

Thanks pmarc & drawoh,you both are very much right, but i have my drawing in that shape so i want to have gage for that,without having any engineering change,can any body suggest ,how it will look like.

 

[ewh]

Not to be too picky, but Y14.5-2009 now specifies what abbreviations are acceptable? Is this directly addressed in the standard? I thought that was the purpose of Y14.38M-2007.

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

 

[MikeHalloran]

Despite all the insance tolerances, there's no BASIC dimension establishing the angular relation of the faces, so you can't begin to inspect the hexagon, or design a gage for it.



Mike Halloran
Pembroke Pines, FL, USA

 

[ewh]

I still can't find where "EQ SP" has been superceded in ASME Y14.5-2008. Can someone help me out here?
I realize that the point I am raising is unimportant in regards to the OP, but it is not unimportant to the use of this forum. If corrections are to be recommended to agree with the standard(s), it is important that those recommendations are actually per the standard, and the correct standard needs to be referenced. Otherwise there will be a tendancy for the advice to be ignored, in the post in question as well as future posts.
I have much to learn about these standards even after using them for the last twenty five years, and can use all the help I can get when they are revised.
Yes I am being pedantic, but when it concerns following standards that is not necessarily a bad thing.


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

 

[pmarc]

ewh,

See fig.4-38 in 2009 standard for equal spacing abbreviation.

 

[ewh]

Thanks, pmarc. My issue is that the figure was not intended to address the change of abbreviation. As has been pointed out many times in these threads, the examples given "are intended only as illustrations to aid the user in understanding the principals and methods of dimensioning and tolerancing described in the text." The text related to that figure are all refering to datums, none to abbreviations. Nowhere in the standard do I find abbreviations addressed directly.
As an aside, I really appreciate that the relevant paragraphs are listed in the lower right corner of the figures. That is a huge help in interpretation.

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

 

[KENAT]

Per 14.38a-2002

EQ = equation

SP = space - as well as about 15 other things.

EQLSP = equally spaced

EQL = Equally

I'd guess 14.5-2009 reference 14.38a-2002 instead of Y1.1 for abbreviations but could be wrong.

Posting guidelines faq731-376

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

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

 

[ewh]

Thanks for that. It doesn't change my stance on using example figures out of context, but it is good to know that it wasn't just an oversite on the part of the editors in the new standard.
FYI, in the new Y14.5 under para 1.2.2 "Additional Standards (Not Cited)" it lists Y14.38M-2007 for abbreviations.
Time for us to put in for a new update, huh KENAT. I'm not holding my breath.

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

 

[KENAT]

Thanks for the chuckle, update, ha, ha.

Posting guidelines faq731-376

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

 

[Tunalover]

This is a perfect example of the good use of profile tolerancing to control shape. Dimension the hex using all basic dimensions then spell out the departures from true position using a bilateral profile tolerance.


Tunalover