Datum on centre axis??

hi every one... today, in one of my drawing I put the datum on centre axis (of cylinder) but my senior told me that it is wrong I cant give datum to the centre axis. But when I was reading about datum I found that we can select the centre axis as our datum... so after reading that I got confused. so can any one help me out in this??
Thanks in advance.

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1 Answer

A datum can be anywhere you like, but a datum is used as a reference, so you need to consider how someone is going to use the center of something as a reference.

For a cylinder, you really only have two choices. The center, or along the outer perimeter. Of the two, I think the center is the better option, but taking measurements from the center will be difficult if there is not a feature like a hole which might be used to help set it up in a lathe, or on live centers.

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