Alignment to offset holes?

Hi all. First post. Sorry if it's a rookie question.

I want to do a Plan-Circle-Circle alignment.
The first hole is the x0 y0 origin.
The second hole has some given coordinates, say x8.0, y4.0.

I don't want to have to calculate the angle and use the "Offset angle" in the "Rotate to" field.
I also don't want to use an iterative alignment.

Any ideas?

Thanks,
Steve

RandomJerk over 8 years ago

Old thread, late to the party, but this should be handled via offset line, offsetting in the direction indicated by the drawing. If you were building a hard gage for something like this with pins, would the rotational datum have a slot parallel to the datum, offset by the single value that controls rotation, or would you slant it by the calculated angle?
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tking over 8 years ago

Old thread, late to the party, but this should be handled via offset line, offsetting in the direction indicated by the drawing. If you were building a hard gage for something like this with pins, would the rotational datum have a slot parallel to the datum, offset by the single value that controls rotation, or would you slant it by the calculated angle?

If both are basic you need to rotate by the trig'd angle. The line method will set one to basic and all error will be forced to the other. Slot would be parallel for the single value, "slanted" for 2 basics.

.02,

TK
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VinniUSMC over 8 years ago

Iterative actually is not the best method for this (unless you are required to maintain car body position, and the CAD isn't square to body lines).
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RandomJerk over 8 years ago

If both are basic you need to rotate by the trig'd angle. The line method will set one to basic and all error will be forced to the other. Slot would be parallel for the single value, "slanted" for 2 basics.

.02,

TK

Look at Fig. 4-46 on page 84 of the 2009 standard.
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tking over 8 years ago in reply to RandomJerk

Last one I bought was 1994 so .............
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VinniUSMC over 8 years ago in reply to RandomJerk

D'oh... 6 and 8 look so similar.
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RandomJerk over 8 years ago

4-46
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VinniUSMC over 8 years ago in reply to RandomJerk

D'oh. Stupid eyes.

That figure still doesn't say what you think it's saying. Yes, the mutually perpendicular plane is offset 15. That isn't the same as saying "use an offset line". You cannot do that with a circle, because it is a closed feature. You have to find the line between B and C and offset rotate by the basic angle. Unless the callout is only basic in one axis.
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tking over 8 years ago in reply to RandomJerk

Yea, what Vinni said!
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RandomJerk over 8 years ago

See, I interpret the figure as showing that the plane is 15 away from the datum, not whatever the value turns out to be after a rotation. Several automotive design engineers I've worked with agree, the offset perpendicular to the specified axis need be exact. And it can make a difference - if nominal center to center is 10, actual is 10.1, and your true position is 0.2, if you rotate you'll be in, but if you offset you-ll be out.

In the end, however others do it is fine by me, though.
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