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View Full Version : Marking the Zero dimension for datum dims?


Steve
03-31-2003, 11:37 AM
I am inserting Short Datum Dimensions on my drawing. This company's standard is to label the datum itself as "0.00". Is there a way to label the datum itself with a zero dimension?

Steve

Steve
04-01-2003, 12:14 PM
So, does anyone know how to get annotation to give you the zero dimension on a series of coordinate or datum dimensions?

Steve

jkramer
04-01-2003, 09:53 PM
Hi,

sorry, I don't know, but we use a sketch consisting of 2 line and two "0" texts that we place on the lower left corner of a Sheet Metal Flat View. (see picture)
We attach all coordinate dimensions to the lines of this sketch, so that if we move the sketch, all dimensions go along with it. The advantage: if the lower or left border of the flat changes, we move the "datum sketch" along, and all dimensions change accordingly. We also attached a (very small) text to the datum sketch, which is found by the CAM system, and used as their datum reference point.

Regards,
Jaap

May Kung
04-02-2003, 08:04 AM
I normally just select the centerline of the datum hole (or some other representative geometry) to get the zero datum. It seems to work. Let's say a datum hole is used as zero. I throw up a centerline for the hole, then start a coordinate dimension. The reference is one of the centerlines (let's say, left half of the horizontal line). I then select the right half as the first point I'd like to dimension.

Jim McKim
04-02-2003, 02:09 PM
I've had some success by dimensioning between two points that are zero distance apart in the direction for which I want it to serve as a datum. This has to be done separately from the rest of the dimensions in that axis, because the order of the picks is opposite. For example, say you are datum short dimensioning left to right from a vertical left edge, with the dimensions appearing along the bottom of the view. First, do what you have been doing, picking the lower end of the left edge as your datum and add horizontal dimensions to the various features across the part. Now, to get the "0.0", start the command all over again, but this time pick the upper end of the left edge as the datum and the lower end (your original datum) as the first feature for a horizontal dimension, and you should get a "0.0" value. This will work using the ends of a centerline as the datum, too.
Actually, it could all be done in one shot, just picking the upper end as the datum and the lower ends of the features to be dimensioned.
One drawback of this method is that your zero is tied to the end of an element that may get affected by model changes.