GD&T Question 3

[Michael Boble]

Hello everyone, could you help me by guiding me in solving the following 2 questions, I am currently studying the subject of GDTS on my own on the internet and I have no one to advise me with my questions

Thanks to everyone for your support!

What is the location tolerance for the 18 holes relative to each other if the holes if the holes are produced at their smallest size?


Calculate the inner and outer boundaries of the 18 holes relative to each others

 

[chez311]

So, try #3 huh? Third times a charm? It still reads like a textbook question but this time just a little less so.

I already got the impression from your previous deleted posts you were doing this for self study and not school coursework, but still "gimme the answer" posts are generally frowned upon here and don't get much traction, especially when its clear the poster has very little grasp on the core concepts. Simply giving you an answer to this question or walking you through the solution would do little to actually improve your knowledge of the subject. The way that you are asking this question shows you have done very little legwork/prior study on this topic and you need to familiarize yourself with the definition of position tolerance, MMC (Maximum Material Condition) position, and composite position. Presumably you are studying ASME Y14.5 ? The standard can be daunting, but it will provide you the information you need. There are also a plethora of online learning resources (actual courses - not just workbooks) for affordable prices to take you through these topics step by step.

I will give you a little nudge however, though the wording is a little ambiguous - the position tolerance "relative to the datum features" (pulled from your other posts, you have deleted it here but it was on the workbook question) likely refers to the PLTZF or upper frame of the composite position tolerance and the position tolerance "relative to each other" likely refers to the FRTZF or flower frame(s) of the composite position tolerance.

 

[drawoh]

Michael Boble,

What is your source for that diagram?

The 0.1mm[ ]dia positional tolerance at the bottom of the FCF for the 18mm holes is normally used to control the quality of the pattern separately from datum features on the sides. This one controls the elevation of the holes from the bottom face. This is weird.

I love calling up zero positional tolerances, but I specify a generous tolerance on the hole size. Your maximum positional error is allowed at LMB, but the drawing above does not provide much of that. The datum[ ]B hole's positional tolerance controls perpendicularity only. The same goes for the datum[ ]C slot.

If I were a fabricator quoting on this drawing, I would contact the customer and make sure they understood what they were telling me to do. Are you sure you are using a good textbook?

--
JHG

 

[greenimi]

Just my guess, looks like Tec-Ease kind of work/ training material

 

[axym]

All,

I agree that the drawing looks like it's from Tec-Ease and would most likely have been created by Don Day.

I actually don't have any issue with the GD&T on that drawing, I would say that it's quite well done. The lower segment of the composite FCF refines the spacing of the 2 holes, and their orientation to the bottom face. It's a composite FCF so the lower segment does not control the translational DOF (elevation).

I also like the way datum features B and C are toleranced. Don Day was a proponent of "exact constraint", in which datum features are designed and toleranced to constrain their assigned degrees of freedom efficiently and not interfere with others. Datum hole B has a small size tolerance and a perpendicularity of zero at MMC, so it would have a snug fit on its simulator and efficiently control X and Y translation without excessive slop and shift. Datum slot C has a small width tolerance and position of zero at MMC, so it would also have a snug fit with its simulator. The fact that C is a slot allows it to efficiently control w rotation (clocking) without interfering with X translation.

I wish I saw more drawings like this in industry.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[greenimi]

I would say 0.1 respectively 17.8/18.4 for the OP's question. Would be nice if someone double check my numbers.

 

[SeasonLee]

Snapshot from the Solution for the ones who need to know the answer.

Season

 

[aniiben]

So what is the correct answer of

"What is the location tolerance for the 18 holes relative to each other if the holes if the holes are produced at their smallest size?"

0.4 or 0.1 or neither?

I am confused.

 

[Belanger]

What is the location tolerance for the 18 holes relative to each other if the holes if the holes are produced at their smallest size?

It would come from the lower portion of that composite FCF (the 0.1); what ASME calls the Feature-Relating Tolerance Zone Framework.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[Michael Boble]

Season Lee.

Is there any chance you could share the textbook solution book with me? I would be really grateful! If possible, I give you my email. I wait your answer

Greetings!

 

[SeasonLee]

Too bad, its my mistake, snapshot the wrong place, here is correct one.

The two original questions looks quite similar

Michael

All textbooks from Tec-Ease is printed version, there is no pdf version, very sorry for I can't share it with you, you may order it online as I mentioned on the other thread.

Season

 

[Michael Boble]

Thanks SeasonLee and to all who helped me, it was very useful ... Greetings !! Stay safe!