Datums in a drawing with thread
Datums in a drawing with thread
(OP)
Hello everybody,
I am new in mechanical design and I would like an advice from professionals. I have a drawing of a part with thread. I wand the part to be very precise and adding a datums is a good option, but this sounds me very lightly, because threads are very loose and even if the part is precisely machined it does not matter. Am I right or I can add datums in this drawing, maybe there is a rule that I don't know?
Thank you!
Ivaylo
I am new in mechanical design and I would like an advice from professionals. I have a drawing of a part with thread. I wand the part to be very precise and adding a datums is a good option, but this sounds me very lightly, because threads are very loose and even if the part is precisely machined it does not matter. Am I right or I can add datums in this drawing, maybe there is a rule that I don't know?
Thank you!
Ivaylo





RE: Datums in a drawing with thread
If you want to specify centreing, and other relations between your features, you need to call up datums. It does not matter how accurately you call them up.
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JHG
RE: Datums in a drawing with thread
If you're European I assume you're working to ISO standards? They have some options for default tolerances that off the top of my head I can't recall how they may play into tolerance of features shown alligned.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Datums in a drawing with thread
Thanks for the fast answers!
RE: Datums in a drawing with thread
I am not sure about ISO, but the ASME Y14.5 standard requires datums to be applied to features, not centre-lines. If you apply datums to the bottom of your part and to the minor diameter of the thread, a positional tolerance on the hole is completely logical.
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JHG
RE: Datums in a drawing with thread
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