Dimensioning an elliptical hole
Dimensioning an elliptical hole
(OP)
Hello,
I'm detailing a drawing that has an elliptcal mounting hole on a bracket. I'm not sure what method of dimensioning would work best.
I thought of locating the center with basic dimensions, definining the feature of size by minor and major diameters with a position callout.
My other idea is to use profile of a surface.
Are any of these options acceptable or is something better I should consider.
Thanks in advance,
Bill
I'm detailing a drawing that has an elliptcal mounting hole on a bracket. I'm not sure what method of dimensioning would work best.
I thought of locating the center with basic dimensions, definining the feature of size by minor and major diameters with a position callout.
My other idea is to use profile of a surface.
Are any of these options acceptable or is something better I should consider.
Thanks in advance,
Bill





RE: Dimensioning an elliptical hole
RE: Dimensioning an elliptical hole
That may work, but I would like to describe my situation a little better in case I'm painting the wrong picture.
This mounting hole is normal to surface, but has the profile of an ellipse. I believe the intent of the design was to create a 2-way locator, but I don't know why an elliptical shape was used instead of a traditional slot.
RE: Dimensioning an elliptical hole
RE: Dimensioning an elliptical hole
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RE: Dimensioning an elliptical hole
Regards,
Bill
RE: Dimensioning an elliptical hole
Dimensioned the Major & Minor 'radius' (basic)
Dimensioned to the center (basic)
Used Profile of a surface.
Had a callout to the Ellipse saying "Ellipse" which the FCF was attatched to.
Can't claim credit for it though, my checker had marked up the print.
To my mind just giving positional for location and the minor and major and not using a profile you're not really fully defining the feature but I may be wrong. Even adding the note 'ellipse' you're still not really fully defining the tolerance all around without some kind of profile.
RE: Dimensioning an elliptical hole
x^2/r1^2 + y^2/r2^2 = 1
So providing the major/minor diameters and the location is enough for the machinist. I'd also say ellipse in a note to decrease confusion.
RE: Dimensioning an elliptical hole
The block tolerance (or tolerance on the dimension) may apply at the max & minor but what about the points in between?
To back this up, on older similar parts the ellipse just had a +- tol on the major and minor dimension. When we put a profile tol of roughly equivalent value on the feature the vendor complained they couldn't meet it. Basically from what we could gather before they were only inspecting the max and min dimensions, not checking the form all around the ellipse.