How to place correct GD & T on eccentric shaft?
How to place correct GD & T on eccentric shaft?
(OP)
Attached is an image of my drawing of an eccentric shaft. I don't think what I have is correct. There are bearings on each of the datums that I have called out (except the keyway of course "G"). The keyway is strictly driving the shaft and its location is probably not critical, but I used it as a datum to orient the shaft diameters in line with it (see the end view, as all the shafts are on the same centerline). I don't think I can call out the centerlines as datums either. I also don't think my runout conditions are called out correctly either. Any help would be appreciated!





RE: How to place correct GD & T on eccentric shaft?
I am not sure what your diameter .438 is.
If it’s distance between the axes, then remove diameter symbol, make dimension Basic, and specify Position on your shaft diameters.
Then we will see.
RE: How to place correct GD & T on eccentric shaft?
He did not think you could have a runout tolerance called out on a datum and I could not find any examples in my gd&t books either. I wonder if I removed the runout condition and did as you said add a position callout to each of the diameters...maybe that would be better? Another thing that is confusing is -what if there were no key seat? How would I define the orientation of each of the diametrical lobes? I would still want them to be in line with each other.
RE: How to place correct GD & T on eccentric shaft?
If you pick two lobes as your datum and apply Position to other lobes wrt first two, they will be oriented to each other by what's known as Simultaneous requirement. Check your GD&T books.
RE: How to place correct GD & T on eccentric shaft?
Frank