Dear guys,

I’m sory because I don’t find a suitable place to post my question

I have 2 dimensions with positional tolerance and profile tolerance. But I don’t understand exactly the meaning of them and the role of them when manufacturing.

Thank you

Categories: Drawings and Detailing

Last comment By: Kevin Chandler   Mon, 23 Apr 2018 13:52:25 GMT
Re: The meaning of positional tolerance and profile tolerance

Hello,

I would recommend that you obtain a copy of the ASME GD&T standard: https://www.asme.org/products/courses/introduction-geometric-dimensioning-tolerancing

Also available is an online introductory GD&T course "https://www.asme.org/products/courses/introduction-geometric-dimensioning-tolerancing" (and there's an advanced course too, but this one is required first).

You can also search (outside of the forum) for examples of "positional tolerance", "profile tolerance", "max material condition", "datum shift".

Cheers,

Kevin

By: Kevin Chandler  Mon, 16 Apr 2018 12:07:35 GMT
Re: The meaning of positional tolerance and profile tolerance

Thanks @Kevin Chandler, I just read the definition of them , but I actually can't understand  how to apply them.

By: Tran Van Quang  Mon, 16 Apr 2018 12:12:34 GMT
Re: The meaning of positional tolerance and profile tolerance

Here is a good place to start:

By: Dan Pihlaja  Mon, 16 Apr 2018 13:30:22 GMT
Re: The meaning of positional tolerance and profile tolerance

Brian McEwen wrote:

I'm not an expert, but in very basic terms: Profile means the shape has to be about the same as the CAD. That tolerance is not tight, has to be within 1mm (to either side) of the CAD profile.

Position GD&T means it has to be within the specified distance/tolerance of ideal position. It is different from a regular ±0.5mm tolerance on a single dimension because it includes any, two dimensional, direction. And the MMC (M inside circle) makes it a bit more complicated.

True Position | GD&T Basics These guys explain it better.

Attached a Genium chart I find helpful. (or get it here Genium Publishing Corporation | Drafting and Engineering )

Correction.  Not 1mm to either side.  1mm TOTAL tolerance.  In other words, a 1mm tolerance zone that is centered on the theoretical exact shape (making it .5mm to either side.

By: Dan Pihlaja  Mon, 16 Apr 2018 13:33:44 GMT
Re: The meaning of positional tolerance and profile tolerance

Thank all guys,

By: Tran Van Quang  Mon, 16 Apr 2018 13:51:29 GMT
Re: The meaning of positional tolerance and profile tolerance

The profile (the curve that is the top of your part ) has a profile tolerance of 1.0 mm with regards to datum feature X primary, datum feature A secondary, and datum feature C tertiary. So if you take that nominal profile, it has to be perpendicular from the the "X" datum feature surfaces along the full profile surface within+/- .5mm. I cannot find your "A" and "C" datum features, so I can't tell what that relationship would be. I'm guessing on the "X's" because they are not identified like a usual datum or datum feature.

The positional has a profile tolerance of .5 mm with regards to datum feature A primary, datum feature C secondary, and datum feature X tertiary. Again i don't think i have the full drawing so I cannot identify those.

By: Jody Smith  Mon, 16 Apr 2018 14:10:25 GMT
Re: The meaning of positional tolerance and profile tolerance

I think datum A and C are the section A-A, C-C in my drawing file

By: Tran Van Quang  Mon, 16 Apr 2018 14:17:28 GMT
Re: The meaning of positional tolerance and profile tolerance

That makes it hard to define then as the GD&T is not implemented correctly, or, at least I am not able to discern what it means based on my rudimentary level of GD&T training. I do apologize. I wish that I could help you more. You have to think of GD&T as a language, and as such, it can be spoken incorrectly and it can be translated incorrectly.

By: Jody Smith  Mon, 16 Apr 2018 15:16:37 GMT
Re: The meaning of positional tolerance and profile tolerance

Tran,

I would highly recommend you begin by reading/watching some of the widely available free material out there on the internet on Geometric Dimensioning and Tolerancing (GD&T) - a simple google or youtube search will pull up a huge list of material that can be read through. A decent introductory class is actually available on youtube if you search "GD&T PT1" or similar - there are several parts. I would also highly recommend purchasing a paid introductory class, either in-person or online (GD&T Basics as someone previously linked to is excellent for beginners/intermediates) and then following that up with a more in-depth study of the Y14.5-2009 standard.

Any explanation that any of us gives you on here is a poor substitute to devoting some time into learning the basics of the concepts and will do very little in advancing your understanding if you don't have a firm grip on the basics - GD&T is a relatively complex topic requiring a 200+ page standard to flesh out (and even that is ambiguous/incomplete at times). It would be the same way if you were asking someone to explain differentials or integrals without having at least a working basic knowledge of calculus.

Additionally if you are asking questions about it and its interpretation in prints I would assume you probably need it in some professional capacity at your job or place of employment. I would again even further highly recommend that you invest some time and resources into learning these concepts as there is quite a bit more to GD&T than just position and profile tolerances. I am saying this from experience as I have tried applying GD&T without fully understanding the underlying concepts and it does not work, at least not well.

By: Chase Evans  Mon, 16 Apr 2018 15:27:59 GMT
Re: The meaning of positional tolerance and profile tolerance

Hello,

If you understand what the parallel tolerance symbol means, then profile is basically the same thing except it's usually used for curved surfaces.

Datum "X" is a target datum and this defined.

Datums A & C aren't defined and can't be assumed. They must be indicated.

And no, they're not the sections.

Cheers,

Kevin

By: Kevin Chandler  Mon, 16 Apr 2018 15:30:37 GMT
Re: The meaning of positional tolerance and profile tolerance

Kevin Chandler wrote:

Hello,

If you understand what the parallel tolerance symbol means, then profile is basically the same thing except it's usually used for curved surfaces.

Datum "X" is a target datum and this defined.

Datums A & C aren't defined and can't be assumed. They must be indicated.

And no, they're not the sections.

Cheers,

Kevin

That isn't actually true.   The parallel tolerance controls form, but not position (in other words, form dimensions, if any would be basic, but positioning dimensions would not be).  While profile of a surface control both form and position, in which all dimensions associated with them would be basic.

By: Dan Pihlaja  Mon, 16 Apr 2018 15:33:12 GMT
Re: The meaning of positional tolerance and profile tolerance

Chase Evans wrote:

Tran,

I would highly recommend you begin by reading/watching some of the widely available free material out there on the internet on Geometric Dimensioning and Tolerancing (GD&T) - a simple google or youtube search will pull up a huge list of material that can be read through. A decent introductory class is actually available on youtube if you search "GD&T PT1" or similar - there are several parts. I would also highly recommend purchasing a paid introductory class, either in-person or online (GD&T Basics as someone previously linked to is excellent for beginners/intermediates) and then following that up with a more in-depth study of the Y14.5-2009 standard.

Any explanation that any of us gives you on here is a poor substitute to devoting some time into learning the basics of the concepts and will do very little in advancing your understanding if you don't have a firm grip on the basics - GD&T is a relatively complex topic requiring a 200+ page standard to flesh out (and even that is ambiguous/incomplete at times). It would be the same way if you were asking someone to explain differentials or integrals without having at least a working basic knowledge of calculus.

Additionally if you are asking questions about it and its interpretation in prints I would assume you probably need it in some professional capacity at your job or place of employment. I would again even further highly recommend that you invest some time and resources into learning these concepts as there is quite a bit more to GD&T than just position and profile tolerances. I am saying this from experience as I have tried applying GD&T without fully understanding the underlying concepts and it does not work, at least not well.

I completely agree with this.  Training is your best friend here.  If this is for consumer products or safety items, you are going to want to dedicate some time to learning this, as the alternative could be a lawsuit or someone getting hurt with the end product.

By: Dan Pihlaja  Mon, 16 Apr 2018 15:48:54 GMT
Re: The meaning of positional tolerance and profile tolerance

Thank you @Jody Smith, I met those tolerance in a drawing, for some reasons I can't post the original file here, but I attached some images for missing datum here.

By: Tran Van Quang  Mon, 16 Apr 2018 16:07:44 GMT
Re: The meaning of positional tolerance and profile tolerance

I'm sorry, I just posted the images for missing datum

By: Tran Van Quang  Mon, 16 Apr 2018 16:10:04 GMT
Re: The meaning of positional tolerance and profile tolerance

Thanks Pihlaja. Good point.

By: Brian McEwen  Mon, 16 Apr 2018 16:17:30 GMT
Re: The meaning of positional tolerance and profile tolerance

Thank  Pihlaja,

I iust start my internship in new company. And one of my first tasks is understanding the specification of product via it's drawing. Frankly, this standard is very new to me, and I think I will save to take a course after I settle down my job in the company.

By: Tran Van Quang  Mon, 16 Apr 2018 16:16:56 GMT
Re: The meaning of positional tolerance and profile tolerance

I'm not an expert, but in very basic terms: Profile means the shape has to be about the same as the CAD. That tolerance is not tight, has to be within 1mm [correction: 0.5 mm] (to either side) of the CAD profile.

Position GD&T means it has to be within the specified distance/tolerance of ideal position. It is different from a regular ±0.5mm tolerance on a single dimension because it includes any, two dimensional, direction. And the MMC (M inside circle) makes it a bit more complicated.

True Position | GD&T Basics  These guys explain it better.

Attached a Genium chart I find helpful. (or get it here Genium Publishing Corporation | Drafting and Engineering )

By: Brian McEwen  Mon, 16 Apr 2018 13:30:36 GMT
Re: The meaning of positional tolerance and profile tolerance

Tran,

First I would see if theres any training or reimbursement for training through your work, I would hope there is if they expect you to read and interpret drawings with GD&T in them. Second, especially if you will be paying out of pocket for any instruction, as I said in my previous post I would definitely start out with the vast amount of free instruction out there available through a simple google and youtube search using keywords like "GD&T intro" or "GD&T 101" etc...

By: Chase Evans  Mon, 16 Apr 2018 16:24:11 GMT
Re: The meaning of positional tolerance and profile tolerance

I'm so busy with my new work, and the disadvantage of searching by google is I can't ask directly my problem

By: Tran Van Quang  Mon, 16 Apr 2018 16:29:32 GMT
Re: The meaning of positional tolerance and profile tolerance

Attached are some references I have put together over the years from the internet.  Hope it helps someone out.

Chris

By: Christopher Estelow  Mon, 16 Apr 2018 16:39:40 GMT
Re: The meaning of positional tolerance and profile tolerance

Thanks @Christopher Estelow

By: Tran Van Quang  Mon, 16 Apr 2018 16:45:30 GMT
Re: The meaning of positional tolerance and profile tolerance

Just be careful that you are not falling prey to this:

By: Dan Pihlaja  Mon, 16 Apr 2018 16:45:58 GMT
Re: The meaning of positional tolerance and profile tolerance

OK you need to read the complete ANSI-ASME Y14.5

By: Ruben Rodolfo Balderrama  Mon, 16 Apr 2018 16:51:23 GMT
Re: The meaning of positional tolerance and profile tolerance

Thank Rubben

By: Tran Van Quang  Mon, 16 Apr 2018 17:04:50 GMT
Re: The meaning of positional tolerance and profile tolerance

Tran so you're telling me you're too busy with your work to learn the skills clearly needed to complete said work? Sounds like you need to discuss that with your superiors.

I must assume that someone at your work has at least a working knowledge of GD&T, at the risk of stating the obvious I would recommend you ask them to help you understand some of these concepts before reaching out to an internet forum and asking basic questions about a topic which has plenty of free resources available to answer these exact questions. I have to assume that you have spent at least 30-45 minutes on this forum asking and responding to questions that could have been better spent watching an introductory 30 minute video on GD&T.

The drawing you provided, with the supplemental snapshots showing the datum definitions, is a very standard datum structure and feature control frame and besides going through every concept you need to understand to interpret it - position tolerance, profile tolerance, datum reference frame, Maximum Material Condition, Maximum Material Boundary, Datum Targets, perpindicularity, basic dimensions, etc... - theres not much else to it. Both of our time would be better spent by you attempting some quick research as there are people out there much more qualified than I who have taken the time to put together definitions, charts, and diagrams outlining these concepts which are much better than I could do in a forum post here. I think several people here have done the work for you and actually provided some of these resources. I guarantee a simple google search would pull up literally hundreds more.

By: Chase Evans  Mon, 16 Apr 2018 17:10:05 GMT
Re: The meaning of positional tolerance and profile tolerance

It has been mentioned, but you should not try to use A-A and C-C section views as Datums.  If someone else at your company already did that, then... you are going to have trouble interpreting their drawings.

One should pick datums that are clear physical feature that someone could put a measuring device on (in the case of a hole one can put in a pin); you can also think about a surface you can clamp to a measuring table as a good Datum.

Standard datum symbol

datums and sections views

By: Brian McEwen  Mon, 16 Apr 2018 17:13:11 GMT
Re: The meaning of positional tolerance and profile tolerance

The Standard ANSI / ASME rules, there isn't nothing that is above it, don't send him to another place. That standard is international.

He must to read this one and apply what is the best suits according to the examples that's inside there.

By: Ruben Rodolfo Balderrama  Mon, 16 Apr 2018 17:21:17 GMT
Re: The meaning of positional tolerance and profile tolerance

Agreed again! Man, I like when you post!!

I have 3 links that I posted that are still in moderation (since 11:30 this morning....I assume that the storm took out Richard Doyle and his crew just like it took out our school this morning [no biggie, Richard, but I mention it just in case I got overlooked.  ] ).

By: Dan Pihlaja  Mon, 16 Apr 2018 17:53:47 GMT
Re: The meaning of positional tolerance and profile tolerance

Chris

By: Christopher Estelow  Mon, 16 Apr 2018 17:57:43 GMT
Re: The meaning of positional tolerance and profile tolerance

Thanks! You have a new one release........

By: Ruben Rodolfo Balderrama  Mon, 16 Apr 2018 18:04:09 GMT
Re: The meaning of positional tolerance and profile tolerance

Ruben,

A few points:

1) The standard you linked to is the 1994 standard which is slightly outdated seeing as there is a 2009 standard released that differs in several key ways and is actually soon to become outdated itself by what I believe is a 2018 standard to be released soon.

2) The ASME Y14.5 standard should absolutely be read thoroughly, however judging by the fact that Tran has already expressed zero interest in even performing a simple google search to find a few learning resources I doubt he will comb through a complex 200+ page standard in its entirety. Additionally the ASME standard, while good, is a poor teaching and learning tool in order to understand some of the core concepts underlying using the actual standard itself - I'm sure there are some people that say otherwise however for the majority of people I believe this is the case. There are a plethora of instructional classes out there, I have taken several - both paid and free - and not one of them runs down the ASME Y14.5 standard line by line to teach the concepts contained in the standard. Indeed is incomplete or ambiguous in several areas requiring some interpretation and understanding in how it is actually being used by professionals in the industry which is outside what is contained in the text.

3) (really 2a) Stating that the only way someone can learn GD&T is by reading the standard is like saying the same about any math class you have ever taken. Did you sit down and read every single proof and theorem that was created to form the concepts you used in class? No - you sat in a class and had an instructor distill them into lessons and concepts you could process. I am only suggesting the same - with of course the caveat that the source material (ASME Y14.5) should absolutely be referenced along the way.

By: Chase Evans  Mon, 16 Apr 2018 18:05:38 GMT
Re: The meaning of positional tolerance and profile tolerance

Thanks - at least someone does haha! I'm trying to provide some advice that I wish someone had given me when I first encountered GD&T however I'm just not sure its getting through........

Yeah FYI your posts are probably being moderated if you have external links in them. I'm just avoiding using external links or url's/web addresses in these forums unless I reeeeally reeeeally have to.

By: Chase Evans  Mon, 16 Apr 2018 18:09:14 GMT
Re: The meaning of positional tolerance and profile tolerance

ANSI/ASME Y14.5 is a standard. You will to know that everyone uses the standard as it's, there is no ambiguous meaning, if I design something here in Argentina it should be understood equally in Japan. I receive designs from Germany, China and other countries and GD & T indications are not ambiguous.

The standard was made so that everyone in the world has the same concept of geometric tolerances.

By: Ruben Rodolfo Balderrama  Mon, 16 Apr 2018 18:15:18 GMT
Re: The meaning of positional tolerance and profile tolerance

As far as I know the -2009 one I attached is the latest one.

Chris

By: Christopher Estelow  Mon, 16 Apr 2018 18:34:28 GMT
Re: The meaning of positional tolerance and profile tolerance

FYI, whichever standard the print was drawn to is the standard you should be following for that specific drawing.

We run into this all the time.   We get prints from our customer that range from the early 1950's to the late 1990's.  Since the standards have changed since then, it would be foolish to rely on the ASME Y14.5M-2009 standard on a drawing that was drawn under the ASME Y14.5M-1982 standard.   It just wouldn't work.

By: Dan Pihlaja  Mon, 16 Apr 2018 18:48:28 GMT
Re: The meaning of positional tolerance and profile tolerance

A little FYI:

ASME, and GD&T is open to interpretation in many aspects.

1 example: Hole angular dimensions about a bolt circle, if they are not basic dimensions are left to the control of the quantity of the angles. If they are basic dimensions then they are exemplified with equal quantity to the amount of holes. Additionally, Equally Spaced is a common call-out but leaves non-basic dimensions with it as a reference able to be over defined. I've seen major aerospace firms do it both and all ways, while still calling out ASME Y14.5.

2. example: Implied Symmetry is not written in ASME, but it is acceptable - or is it not.

NOTE: SolidWorks still to this day does not have a method to be able to create a proper ASME centerline or line of symmetry (shown in ASME Y14.2. Fig 3-1, page 7).

By: S. Casale  Mon, 16 Apr 2018 18:58:58 GMT
Re: The meaning of positional tolerance and profile tolerance

Profile of a surface and profile of a line are different, and mean different things.

Profile is used on many more things than curved lines.

Profile is pretty amazing, it can be a blanket tolerance for how a part is made.

By: S. Casale  Mon, 16 Apr 2018 19:00:23 GMT
Re: The meaning of positional tolerance and profile tolerance

Of course! My point in saying that was only that he presented the ASME standard as gospel and no other resources were acceptable to utilize when learning GD&T concepts while simultaneously posting a link to an outdated standard. I thought the contrast was funny.

I fully understand the need for interpreting a drawing under the applicable standards that the designer was using to produce the print and I should have said as much, my mistake.

By: Chase Evans  Mon, 16 Apr 2018 19:08:18 GMT
Re: The meaning of positional tolerance and profile tolerance

It goes without saying that the ASME standard is the primary document that dictates all the requirements and allowed utilizations of gdnt. I am aware what a standard is and is used to accomplish.

However if you dont see the value in utilizing classes and books and other instruction tools to suppliment the Y14.5 standard im not going to waste anymore time trying to convince you otherwise. Some of us mere mortals need a little help when trying to learn some of the more advanced topics.

Also your statement that the ASME standard is perfect in every respect and requires no interpretation in any topic and explains everything perfectly in perfect language tells me you haven't really gone through the standard thoroughly....

By: Chase Evans  Mon, 16 Apr 2018 19:20:37 GMT
Re: The meaning of positional tolerance and profile tolerance

I think you worked for the automotive industry, Product engineer don't accepts ambiguous interpretations. They use the standard as it's. Unless they have made a drawings with some errors (they are very rarely)

By: Ruben Rodolfo Balderrama  Mon, 16 Apr 2018 19:21:01 GMT
Re: The meaning of positional tolerance and profile tolerance
By: Dan Pihlaja  Mon, 16 Apr 2018 13:42:23 GMT
Re: The meaning of positional tolerance and profile tolerance

Just followed this to the end so I can learn more of GD&T.

Man am I glad most of the shop here has a hard enough time reading regular prints. I wouldn't dare putting GD&T on the prints because we have learned anything that isn't printed in clear English (or Spanish) just gets ignored. To some extent that includes weld symbols.

By: Jim Steinmeyer  Mon, 16 Apr 2018 19:58:30 GMT
Re: The meaning of positional tolerance and profile tolerance

Thank @Dan Pihlaja,

The most difficult I meet with those tolerance is not the main dimension of it , but it is the reference datum (example  here is : A, C, X). I have many drawingS of similar part like this but with same profile tolerance at similar position, they use different reference datum. Are those  reference datum only have role to build reference frame or anything else. And why need MMC for a reference datum with only is theoretical.

By: Tran Van Quang  Tue, 17 Apr 2018 10:40:00 GMT
Re: The meaning of positional tolerance and profile tolerance

MMC (and LMC) allows extra variation if the manufactured portion of that part falls into certain criteria.  This makes things cheaper.   Having MMC on a hole means that if they hold the hole to the larger end of the size tolerance, then that allows them some bonus tolerance on position, making it cheaper and easier to manufacture.  Same thing with a datum.  There is bonus tolerance at play here (although MMC or LMC on a datum is a bit more complicated).

By: Dan Pihlaja  Tue, 17 Apr 2018 13:11:44 GMT
Re: The meaning of positional tolerance and profile tolerance

do a google search for gd&t color chart

By: David Matula  Tue, 17 Apr 2018 13:21:04 GMT
Re: The meaning of positional tolerance and profile tolerance

May you give me an example with datum in my above drawing, I can't identify the reference frame of it. I'm reading ASME about it, but don't understand about the relation of reference datum, the book said it must have precedent to choose reference datum.

By: Tran Van Quang  Tue, 17 Apr 2018 13:26:56 GMT
Re: The meaning of positional tolerance and profile tolerance

The bottom line is that you will have to put some time in to learn GD&T in order to interpret drawings correctly.  Once you get it an really understand it it will be like second nature to you.  Please know that this will most likely not be a very quick journey as you will most likely learn something new every day.

Chris

By: Christopher Estelow  Tue, 17 Apr 2018 13:27:41 GMT
Re: The meaning of positional tolerance and profile tolerance
By: Dan Pihlaja  Tue, 17 Apr 2018 13:30:06 GMT
Re: The meaning of positional tolerance and profile tolerance

There are some guys out there that would come to a user group and did a presentation on it.  They would also do training at companies.  it was awesome how they showed how far off a part could be with standard tolerances and how one could interpret a drawing so that a part could be in tolerance but look nothing like what you modeled.

By: David Matula  Tue, 17 Apr 2018 13:35:34 GMT
Re: The meaning of positional tolerance and profile tolerance

The company I worked for back in the day had a company come in for a week long training session.  What I learned that week was probably the most valuable information that I was ever taught.  I HIGHLY recommend it to anyone who does mechanical drafting/design.  They also had the demo that showed how far off the print a part could look and still pass inspection.  It was mind blowing!!!

Chris

By: Christopher Estelow  Tue, 17 Apr 2018 14:21:08 GMT
Re: The meaning of positional tolerance and profile tolerance

Training is really what I need most now

By: Tran Van Quang  Tue, 17 Apr 2018 14:24:24 GMT
Re: The meaning of positional tolerance and profile tolerance

if you study the color chart it will kind of explain what everything means.

these guys are good

By: David Matula  Tue, 17 Apr 2018 15:28:45 GMT
Re: The meaning of positional tolerance and profile tolerance

Yes, I'm working in company product part for car.

By: Tran Van Quang  Tue, 17 Apr 2018 15:34:18 GMT
Re: The meaning of positional tolerance and profile tolerance

Hello, I want to ask more little about reference datum. In the case in my images, I don't understand why do we need 3 datum reference: A, C, X. I think with only A and C we can build a reference frame. May anyone help me, thank you

By: Tran Van Quang  Mon, 23 Apr 2018 13:36:21 GMT
Re: The meaning of positional tolerance and profile tolerance

Tran Van Quang wrote:

Hello, I want to ask more little about reference datum. In the case in my images, I don't understand why do we need 3 datum reference: A, C, X. I think with only A and C we can build a reference frame. May anyone help me, thank you

Hello,

We have no knowledge of the function of this part, its mating part(s) or of the entire assembly.

Also, I'm not seeing an X datum.

It may have been removed due to a previous post, but since this post has 54 replies so far, I haven't followed along.

To me, it's turned into more of a do my homework for me post than a work post.

Cheers,

Kevin

By: Kevin Chandler  Mon, 23 Apr 2018 13:52:25 GMT