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Another Angled Hole Positional Tolerance Question 4
- Thread starter R1chJC
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I would not dimension that way. Using A as primary I would dimension to the place the axes intersect that feature and show the angle with respect to that surface. In the sketch it is implied that the angled surface plays some part in locating those axes, but that isn't a surface that is referenced.
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R1chJC,
Yes, it is legitimate, just not necessarily the best dimensioning scheme. Fixturing it to hit your Ø0.1mm positional tolerance will be a challenge. As the designer, I would be looking for a way to open that up.
I am not going to propose a dimensioning scheme because I do not know how your part works. If perpendicularity to the angled face matters, you need to specify a datum, and call it up on the block. You can add a second line to your feature control frame with the additional datum.
--
JHG
Yes, it is legitimate, just not necessarily the best dimensioning scheme. Fixturing it to hit your Ø0.1mm positional tolerance will be a challenge. As the designer, I would be looking for a way to open that up.
I am not going to propose a dimensioning scheme because I do not know how your part works. If perpendicularity to the angled face matters, you need to specify a datum, and call it up on the block. You can add a second line to your feature control frame with the additional datum.
--
JHG
I would second 3DDave's conclusion - your x-dimension is dangling and is not fixed so it will change depending on where along B it is taken. It should be dimensioned from the origin created by the intersection of your datums.
See attached for an example, the figure is closer to the A|B|C DRF in your original post/attachment but can obviously be extrapolated to your modified D|B|C DRF.
See attached for an example, the figure is closer to the A|B|C DRF in your original post/attachment but can obviously be extrapolated to your modified D|B|C DRF.
pylfrm,
You're right - I think I disliked the way that [D] is potentially backdriven in orientation from using the angle dimension on the holes and misinterpreted that dislike.
A dimension parallel to [D] and to the intersection of with [D] avoids the ambiguity.
You're right - I think I disliked the way that [D] is potentially backdriven in orientation from using the angle dimension on the holes and misinterpreted that dislike.
A dimension parallel to [D] and to the intersection of with [D] avoids the ambiguity.
Hi All,
Keep in mind that the arrangement of the basic dimensions does not affect the tolerance specification in any way. The only thing that matters is the datum feature referencing.
If the drawing referenced the CAD model and dimensions X, Y and Z were omitted, then the tolerance specification would still be the same. Each hole axis has a theoretically exact orientation and location relationship to the datum reference frame, and it doesn't matter how those theoretically exact relationships are dimensioned (or at all). The basic distance and angle dimensions would not be measured on the actual part - they are only used to lay out the position zones.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
Keep in mind that the arrangement of the basic dimensions does not affect the tolerance specification in any way. The only thing that matters is the datum feature referencing.
If the drawing referenced the CAD model and dimensions X, Y and Z were omitted, then the tolerance specification would still be the same. Each hole axis has a theoretically exact orientation and location relationship to the datum reference frame, and it doesn't matter how those theoretically exact relationships are dimensioned (or at all). The basic distance and angle dimensions would not be measured on the actual part - they are only used to lay out the position zones.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
Evan,
That's a great point and is also an unrelated 'what if' because this is not a CAD model where a programmer has taken some other dimensional input and predigested it for the user.
In this case, the holes are dimensioned to be both nominally perpendicular to [D] and at an angle of Y degrees to . This has the effect of saying the nominal angle between and [D} is determined by the dimension that locates the holes. Dimensioning to the intersection of and {D] eliminates that back-driving for the person who has to do the layout.
That's a great point and is also an unrelated 'what if' because this is not a CAD model where a programmer has taken some other dimensional input and predigested it for the user.
In this case, the holes are dimensioned to be both nominally perpendicular to [D] and at an angle of Y degrees to . This has the effect of saying the nominal angle between and [D} is determined by the dimension that locates the holes. Dimensioning to the intersection of and {D] eliminates that back-driving for the person who has to do the layout.
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- #15
CheckerHater
Mechanical
Or maybe something like this:
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
In the latest post from SeasonLee with the "Before" and "After" sketches shown, may I ask you why the "After" method is the preferred one?
Does anyone can offer the relevant verbiage from the book? What would be the justification in the textbook?
I am trying to learn something here.
Does anyone can offer the relevant verbiage from the book? What would be the justification in the textbook?
I am trying to learn something here.
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