Parallel Requirement On Part of a Surface 2

[aardvarkdw]

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

 

[KENAT]

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.

 

[aardvarkdw]

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.

 

[ctopher]

Maybe something like this?

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

 

[aardvarkdw]

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

 

[thundair]

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.

 

[ctopher]

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)

 

[ringman]

Aardvard,

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

 

[MechNorth]

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

http://www.profileservices.ca

 

[ctopher]

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.

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

 

[aardvarkdw]

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

 

[aardvarkdw]

For option "a" I mean.

 

[MechNorth]

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

http://www.profileservices.ca

 

[ctopher]

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



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

 

[dingy2]

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.

 

[MechNorth]

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

http://www.profileservices.ca

 

[dingy2]

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.

 

[aardvarkdw]

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.

 

[aardvarkdw]

Is this acceptable? Based on Y14.5M section 6.3.1.2.

http://i10.tinypic.com/2hno0fb.jpg

 

[thundair]

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.