【转帖】runou

yang686526

runout
i have received a drawing, and for ease of clarity it is a cube with a bore machined straight thro from one side to another (left to right say) the drawing office have a runout tolerance on this bore, but the datums for the runout are the left hand face and the bottom face, this cannot be the correct way to datum this, can it ???
i have never seen this done before
thanks  
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if a separate part goes thru the hole, use position and add a projected tol zone...remove runout.
chris
solidworks/pdmworks 08 3.1
autocad 08; catia v5
a seperate part does go thro the bore (piston) but my problem is that this is a customers dwg (who insists the dwg is correct !!!)
is the datum on each of the faces or on the dimension?  if it is on the dimension, then it would imply the centerlines of the opposing faces, as if clamping in a 4-jaw chuck.
i've never seen runout with anything but round datums.
runout controls surfaces relative to an axis.  the drawing as i understand it (surface to two planes) is wrong.  appropriate datum features would be one or two diameter dimensions, or one diameter and a perpendicular face.

the datum is on each of the planes (faces bottom & left hand side) have informed them that runout is axial
thanks to all
to refine steve's post, runout controls require a datum axis of revolution that could be used to generate that feature.  i bring this up because i have seen drawings with the following scenario; picture a shaft with a timing hole offset from the axis of the shaft, and that timing hole being used as the datum axis for a runout control on the shaft.
jim sykes, p.eng, gdtp-s