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profile tolerance

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BluTurtle

BluTurtle

Coastal
Sep 29, 2009
178
Simple question.
In the image does the highlighed GDT frame have any control over the basic dim 30 deg.



Does it mean the anglar surface can offset 0.3 ?
 
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Can't access the image.

If the profile tolerance points to a surface that is at 30 degrees to a datum, and that datum is mentioned in the feature control frame, then the answer would be yes


John-Paul Belanger
Certified Sr. GD&T Professional
 
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Sorry, I mean that the profile would be controlling the 30 degrees. To say if it's 0.3, I'd have to see the picture.

John-Paul Belanger
Certified Sr. GD&T Professional
 
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Yes it does. We have both a basic 30 degree orientation and also a basic dimension of 30 mm.

Like the drawing too. What program was used to create it if you don't mind? Thanks

Dave D.
 
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blanger - you said that profile would be controling the angle. As far as I know, the tolerance on angle should be plus/minus deg or min. From the pic, how much tol does the angle 30 deg have?

This isnt my drawing, i downloaded from on of the posts here.

I am trying to learn interpret this dwg.
 
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BluTurtle,

The profile tolerance indirectly controls the orientation of the surface, by confining it to a zone that is at the 30 degree basic angle. The 30 degree angle doesn't have a direct tolerance associated with it.

Dave,

The drawing is from one of Don Day's tips of the month on the Tec-Ease site. Jim Sykes would know what Don uses.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
 
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Don uses SolidWorks but I don't know that SW does the yellow shading or if that is done by post process artwork.
The angle is controlled by a total width zone between two parallel planes that are 0.3mm apart perfectly located and oriented to the DRF by the BASIC dimensions.
+/- cake shaped zones for angles is something to avoid. :)

Norm Crawford
GDTP-S
Applied Geometrics, Inc.
 
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NC,
Thanks for explaining. I understand you point about avoiding the cake shaped tolerance zone.

Talking more about the value, in the feature control, 0.3 is actually split on either sides of the 30 deg plane.
That is + or - 0.15

Am I correct in saying so?
 
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Yes. The default for Profile is equal bi-lateral with regard to the true (BASIC) profile.
Unequal and unilateral can be specified for profile also.

Norm Crawford
GDTP-S
Applied Geometrics, Inc.
 
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Just to dig more,
Incase I dont want to dimension the basic 30 (In the image, its shown below the basic 10). Alternatively, Is it good practice to add 2 new dims instead.

1. major slope to datum A
&
2. Minor slope to datum A

Which one of it is consider a better practice?
 
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You could just have one BASIC dimension perpendicular to datum A and at either vertex of the slope. You do not need both given the BASIC angle. However, I would most likely use the vertex used for the BASIC angle just for clarity.
But to be clear, there is nothing wrong with the way it is already shown.

Norm Crawford
GDTP-S
Applied Geometrics, Inc.
 
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OK, I'll bite: "cake shaped zones are to be avoided" because?
(bite-cake)
Frank
 
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Don's graphics do indeed start in SolidWorks, then the extra annotations are added in other software; there's a few that we use depending on what we're trying to convey.

I use the term "wedge-shaped", but cake is good too. The problem with +/- tolerances is that they usually don't tell you where to measure from ... inflection at the top or bottom or somewhere in between ... it makes a huge difference on the tolerance zone which is VERY tight (i.e. perfect) at the inflection point and grows as you move away from that point. When someone tells me that's what they want I ask them to explain to me why the surface is more important at that one point than it is farther away. The exceptions that I've encountered are optics & acoustics which both physically and mathematically use +/- degrees.

Jim Sykes, P.Eng, GDTP-S
Profile Services TecEase, Inc.
 
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I say "cake shaped" because I don't know why everybody refers to a "wedge" as "pie shaped". I cut my cake with the same shape as I do my pie. It's a mood thing. Kind of like how people "feel" what they think they kind of meant when they put silly simple +/- dimensions on non-features of size. :)
Then try to reproduce quality tooling when the tools wear out.

Norm Crawford
GDTP-S
Applied Geometrics, Inc.
 
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Most pies are round, so get cut into wedges - like cheese.

Many cakes are more like a loaf, so a slice wouldn't' be a wedge.

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
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