×
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!
  • Students Click Here

*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.

Students Click Here

Jobs

True Position of Rectangular Slots

True Position of Rectangular Slots

True Position of Rectangular Slots

(OP)
Hi,

If I call out the true position of a rectangular slot in only in the x direction, does that apply in the Y direction as well or only in the X direction?

thanks

 

RE: True Position of Rectangular Slots

If you apply only in X direction it can't be applied to Y direction. You need another callout for position in Y direction.

RE: True Position of Rectangular Slots

(OP)
can I call it out only in the X direction? and then straight dimension the Y locations?  

RE: True Position of Rectangular Slots

You can do that, in fact with 'notches' in the edge of the part that's often how it's done.

However, if a complete 'slot' I'm wondering why not use position in both directions, and look into the "boundary" concept?

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: True Position of Rectangular Slots

(OP)
in the X direction the slots are tappered on both walls and in the Y direction only one wall is tappered. So In the Y direction I have a flat surface that a part butts up against, so I want to control the location of that surface and not the entire slot.  

RE: True Position of Rectangular Slots

(OP)
Hey Kenat,

what does FCF stand for?

thanks for all your help by the way

RE: True Position of Rectangular Slots

It would not be in accordance with any GD&T standard I am aware of and I would not encourage to do so. But of course you can try - it would be some kind of combination of geoemetrical tolerancing and coordinate dimensioning. I do not see a benefit of such combination however.

RE: True Position of Rectangular Slots

That sketch is waaaaay different than I had even imagined. I'm not sure you can use position at all here since there is not a real feature of size to use. Profile of a surface is probably more appropriate.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: True Position of Rectangular Slots

(OP)
that would be an iregular feature of size right...so I can't use true position buy I could use surface profile and then add basic dimensions to datum C to control the positions to that datum. would I call out profile in both directions?

RE: True Position of Rectangular Slots

I would love to know the function of that?
Frank

RE: True Position of Rectangular Slots

It sure looks like a feature of size to me and positional is appropriate.

Dave D.
www.qmsi.ca

RE: True Position of Rectangular Slots

It doesn't seem to meet the definition of a feature of size. What as I missing Dave?

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: True Position of Rectangular Slots

powerhound:

These are tapered square holes with positional tolerance in one direction only.  

Dave D.
www.qmsi.ca

RE: True Position of Rectangular Slots

And we are dangerously closing to the issue of tapered feature being a feature of size or not...

I am with powerhound on this - tapered features or cones are not features of size so profile tolerance is more appropriate way to go - but that's just my opinion. They indeed have opposite points, but they are not associated with unique single size. How could somebody try to apply bonus tolerance concept to that? Which size should be used for bonus calculation?

I do not want to open this can of worms again. I think we had the discussion enough times before.

RE: True Position of Rectangular Slots

Same old argument about FOS vs non-FOS.  No directly opposed sides, not a classical FOS in '94.  '09, ok.
Also, no tolerance on the width of the feature.  And the location dimension from the edge to the center of the datum-C feature is not basic.  
Profile is a far better choice.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: True Position of Rectangular Slots

I agree that the feature does not fit a definition of a feature of size per 94 standard but does fit it in the 2009 1.3.32 (b) "a directly toleranced feature or collection of features that may contain or be contained by an actual mating envelope other than a sphere, cylinder or pair of parallel planes."

Dave D.
www.qmsi.ca

RE: True Position of Rectangular Slots

(OP)
working in ASME Y14.5-2009

RE: True Position of Rectangular Slots

Jim:

You stated "Also, no tolerance on the width of the feature.  And the location dimension from the edge to the center of the datum-C feature is not basic.  
Profile is a far better choice. "

I agree that the tapered holes do not show size tolerances and they must. I have a hard time understanding why there needs to be a basic dimension from datum C to the edge unless the edge is shown in a profile. I do see a .526 dimension.

If the holes were toleranced, we could calculate the MMB of each hole in one direction so I would rather use positional versus profile. It is possible to have a checking fixture with tapered pins locating on true position for the location of the holes in one direction.

Dave D.
www.qmsi.ca

RE: True Position of Rectangular Slots

The .526 dimension is not directly toleranced, nor can it be.  Please show me how you would hold a measuring tape at the center of the slot.  It's not marked as basic either.  In essence, it's an inappropriate dimension.  There are different positional controls at the top and bottom of the slot; what controls the faces in between?  There is a 4-degree dimension, but does the designer really want an angular tolerance zone?  At which point is the inflection of the angular tolerance zone; top, bottom, mid, somewhere else?  You can do a unilateral profile tolerance if that's the goal you seek.  Profile is by definition a boundary control rather than a control of absolute position and absolute size.  I would reject a drawing like this unless the designer could prove to me that all of these questions (and more) are fully resolved.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

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