INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Parallel Requirement On Part of a Surface

Parallel Requirement On Part of a Surface

(OP)
I have a round, flat part with a hole in the center. It kinda looks like a huge washer. Datum A is the bottom surface. How can I get a parallel tolerance of .001in to Datum A for theoretical area 12in in dia. from the center of the part and then the remainder of the part has a parallel tolerance of .003in? Right now there is a FCF with a parallel symbol and no tolerance that references a flag note which says, "TOP SURFACE TO BE PARALLEL TO DATUM -A- TO WITHIN .001" INSIDE n12.000" FROM CENTER CUTOUT AND .003" ACROSS THE REST OF THE SURFACE."

Is this alright or is there a better way. Any suggestions are helpfull. Let me know if you need a pic in order to visualize this.

David

RE: Parallel Requirement On Part of a Surface

How about adding a phantom line circle 12" in dia centered in the part center and then applying cross hatch to that area.  You could then have feature frame labelled 'hatched area' or 'shaded area' or what ever terminology you use, with the .001 requirement.

You could then have a separate feature frame for the rest of the surface.  Not sure if you'd need to label it  'except shaded area' or something.

If it's a fairly busy drawing though the shading may not work well.

Just an idea for you to play with and everyone else to pick apart.

While the note is probably adequate a picture paints a thousand words as they say.

RE: Parallel Requirement On Part of a Surface

(OP)
That is essentially what I was thinking as well. One stupid question though, would you attach the FCF to the shaded area with a leader and a dot instead of an arrowhead? I have only found examples in the ASME Y14.5 standard that show FCF's attached to the profile of a surface.

RE: Parallel Requirement On Part of a Surface

Maybe something like this?

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

RE: Parallel Requirement On Part of a Surface

(OP)
Chris,
Exactly. Your example works for me, anyone want to dispute it?

RE: Parallel Requirement On Part of a Surface

You can't find a sharper pencil on this forum than Chris
But I will add that we often use a phantom line instead of a centerline to define the 12.00 dia circle.

Cheers

I don't know anything but the people that do.

RE: Parallel Requirement On Part of a Surface

Thanks.
True, I would use a phantom line. I was just trying to show an example. Wasn't thinking about the line type.
Nice catch!

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

RE: Parallel Requirement On Part of a Surface

Aardvard,

I think a chain line might be appropriate for designating the 12 in dia.

RE: Parallel Requirement On Part of a Surface

2
Close, Chris, but no cigar.  By putting the parallelism control with the dimension, you are indicating a parallelism control for the axis of the dia-12in circle (ASME Y14.5M-1994 Fig. 6-31, 6-32, 6-33).  Also, controls are to be shown on the edge-view of the surface.

I've posted a couple of alternatives (http://www.profileservices.ca/files/tidbits/tidbits_missc.html) under this thread #.  The phantom line indicates the zone of interest, and cross-hatching would not be necessary because a circle indicates the region within its boundary, not outside of it.  Alternative (a) would be what you were specifically asking, but you would also need to tolerance the thickness of the disc.  My preference is option (b).  The first line of the composite surface profile locates the surface (i.e. acts as a thickness tolerance), and the second line provides an orientation (parallelism) refinement wrt Datum-A.  A second FCF within the same note provides the parallelism restriction for the defined zone.  Alternatively (not shown) the second FCF in (b) could call out a surface profile with the same tolerance value and same datum reference, again for Zone-E.

Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca

RE: Parallel Requirement On Part of a Surface

Jim,
I understand. You are correct. I also thought of showing at edgeview of the surface, but wanted to just show a quick reference to indicate what David (aardvarkdw) was trying to explain.
I didn't have ASME Y14.5M-1994 at work to look up details.
Nice link. I will bookmark.
I don't smoke anyway.thumbsup2

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

RE: Parallel Requirement On Part of a Surface

(OP)
Thanks Jim. Would I want to put a "Seperate Requirements" note on the FCF's so that they arn't applied together?

RE: Parallel Requirement On Part of a Surface

(OP)
For option "a" I mean.

RE: Parallel Requirement On Part of a Surface

Chris, I remember how easily I was confused and swayed by some early instructors' graphics that were "just to illustrate", but unfortunately didn't conform to any single GD&T standard (it was an amalgamation of ASME, ISO, and in-house ramblings).  Same thing for the intentionally incomplete drawings in the standard.  I decided that if/when I started teaching, I'd try to give the "full picture".  I can appreciate now how difficult it is to create training and reference material that is thorough, but not confusing.  

David, "SEP REQMT" would be inappropriate here.  A tip to remember is that SIM REQMT is only automatically invoked for patterns of features (Y14.5M-1994, 5.3.6.1, 5.3.6.2).  As a surface control is being applied, it is not a pattern of features.

The control for Zone-E (second FCF) is a separate control from the overall parallelism, and does not conflict with it.
An interesting aside, SIM REQMT is NEVER assumed for Profile tolerances, so "SEP REQMT" would never have to be called out for the Surface Profile.  

Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca

RE: Parallel Requirement On Part of a Surface

I think being away from engineering, now IT for almost a year, I'm losing it!cry
banghead

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

RE: Parallel Requirement On Part of a Surface

MechNorth is correct but there is another way of reflecting parallelism using Chris' drawing.

One could reflect a basic dimension dimeter using phantom lines and a hatched area as Chris has suggested to show the partial surface where the restricted parallelism tolerance is allowed. The FCF would then be shown to the surface using a leader line with a ball or round end rather than an arrow head.

That would do it.

Hope this helps.

RE: Parallel Requirement On Part of a Surface

Dingy2, I don't recall any samples of that in Y14.5M-1994, but I seem to remember it from a draft of Y14.41 (Digital Document Standard).  Is that the source?  I think it's time I acquired Y14.41.

Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca

RE: Parallel Requirement On Part of a Surface

MechNorth

I was a bit incorrect in my previous answer. The area of interest should be shown with a chain line boundary and hatched lines fig. 1.11 rather than phantom lines.

Since this is not a feature but a theoretic diameter of interest such as location datum targets or true position of holes, I would use a diameter of a basic dimension. 1.7.3.3 states "appropriately dimension".

The use of a leader line to reflect surface is shown on 1-12.

Not everything in life has an exact example in the standard. Sometimes in the standard, there are examples which are not practical such as using MMC on a datum feature of size when the actual tolerance is in RFS (profiles as an example. Love to see someone check that on the shop fllor.

Other times, one would have to extrapolate from the standard for the particular application.

RE: Parallel Requirement On Part of a Surface

(OP)
Jim,

"Also, controls are to be shown on the edge-view of the surface." Is this specified in the standard? I can only find section 3.5 in reference to FCF placement.

RE: Parallel Requirement On Part of a Surface

Two things

One: The parallelism in Chris's sketch can only apply to Datum -A-, whether it is shown from the side or not.

Second: The phantom line would represent both the required area and the position of the component that drove that requirement.

This stuff makes you think. As an old checker I am very seldom challenged, and that makes you dumber every day

I don't know anything but the people that do.

RE: Parallel Requirement On Part of a Surface

aardvarkdw,
It is almost the same as mine.
For most companies and machine shops, they will understand.
MechNorth's description would be correct, but a lot of companies don't use or understand much of GD&T.

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

RE: Parallel Requirement On Part of a Surface

Dingy2, You are correct on the use of the chain line vs the phantom line, and the hatching.  I was thinking it was the same as for datum targets which use phantom lines.  Unfortunately, many CAD systems still make it difficult to hatch a non-section, so it tends to be omitted.  The use of the leader to the surface is arguable, but the Y14.5 standard doesn't show any GD&T application to isometric views, only to profile, plan and sectional views.  That's why my question re Y14.41, because I had understood that standard was to address GD&T applications on isometric views, solid models, etc.  Another problem that is encountered is the inability of some CAD packages to allow you to change the line type to dashed as needed for leaders to show that a control is applied to the back face rather than the front face.

David, there is a note in the book (I had the page last night, but can't relocate it right now) that indicates dimensioning and such are to be done on the profile views ... it may say SHOULD be, but I can't recall.  Another reference is made to it in 6.4.1.1 - Straightness Tolerance ... "A straightness tolerance is applied in the view where the elements to be controlled are represented by a straight line."  Similarly for Flatness 6.4.2.1, and for Profile 6.5.1(a).  This document was originally meant for 2-D drafting rather than the 3-D world we now work in, so some major extrapolations are now needed.  Again, I thought Y14.41 was supposed to clarify the application in that environment.  
The image you posted on tinypic looks good.  I would suggest adding a centerline in the side view and a general tolerance for the other dimensions.  I hate to keep saying "problems with CAD", but it's true; in this case, most CAD packages would have a hard time keeping the chain-line associative with the part geometry, so any changes could easily shift the chainline wrt the centerline of the geometry and confuse the user.
peace

Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca

RE: Parallel Requirement On Part of a Surface

Right on Jim... we have been in Model Base Definition for over a year now and it is hard to imagine going back to anything in  2D.
Our FT&A only allows us to pick a view plane and point to the surface we are trying to control. With boundary's like uni-tolerance on profiles or limited tolerance like Chris's example is difficult for now.
We cover most with field notes just like the originator of this thread, David.

Cheers

I don't know anything but the people that do.

RE: Parallel Requirement On Part of a Surface

Doesn’t this just highlight what we are all up against? The OP asked the question how do you show the flatness tolerance on a washer.

Many people have come up with different ideas and people who post on here regularly and quote standard this or that still get it wrong.

As far as I can see only MechNorth has it right (and I may be wrong about that) and we are talking about the flatness of a washer, not parallelism, concentricity, tolerances of the OD and ID, material specs and all the other bits and bobs.

If we cannot get on simple thing right on the most basic of parts what hope do we all have?

RE: Parallel Requirement On Part of a Surface

Ajack1 - No hope at all of gaining absolute consistency...that's why we all still have jobs!  I also believe it was set up this way by the founding fathers of GD&T to give engineers something to debate professionally so that their wives can't say "Why are you always arguing with our friends!?"
elephant2

Jim Sykes, P.Eng, GDTP-S
Profile Services
CAD-Documentation-GD&T-Product Development
www.profileservices.ca

RE: Parallel Requirement On Part of a Surface

We also can not get it right without knowing the design. If he wants parallelism, I try to help with it. If it should be flatness, probably, but wasn't the question.
I try to make my responces short. I'm not a trainer here, just a helper.
We all do what we can and just have fun with it.
cheers

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

RE: Parallel Requirement On Part of a Surface

Sorry ctopher my mistake he does state parallelism and not flatness.

The point I was trying to make (badly) was that even with the simplest of parts and with only one critical feature people who seem to know what they are talking about still get it wrong, what chance do we stand with complicated parts and many critical features?

RE: Parallel Requirement On Part of a Surface

(OP)
The best you can do, I guess, is to get as many "opinions" as possible and make an educated decision as to what will best convey the information. As I frequently do by comming here when I am unsure of my own reasoning or can't find any definitive information to validate my reasoning.

RE: Parallel Requirement On Part of a Surface

Yes, that is all you can do.
Getting a copy of the specs in addition to posting questions here, you will get your answers.
Thanks guys!cheers

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

RE: Parallel Requirement On Part of a Surface

ajack1

From a couple of conversations I've had with someone who should know even those on the asme y14.5 committee don't always agree on the best way to dimension/tolerance things.

Some have particular favourites, such as profile, while others use the full range of methods as they see appropriate.

I will admit I didn't refer to the spec before giving my original post and didn't think it through, it was just a quicky to give aardvarkdw and anyone else who wanted to something to think about.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close