MCRodg
Mechanical
- Aug 9, 2017
- 11
I have a simple pin that is not intended to rotate in its hole but needs to be a close tolerance fit.
I am undecided if I should callout out Total Runnout or simply straightness, and by straightness I mean the Axial type, i.e. straightness applied to the diameter callout not pointing at the surface. Picture(s) attached.
Every example of total runout I've seen shows at least two diameters on a shaft, the diameter that is controlled by the total runout and at least one other different approximately concentric diameter to use a datum. Sometimes there are two smaller diameters at each end (typically for bearings) that are used as datums to form a datum axis (Datum A-B for example. Pictures attached.
These are for rotating shafts and I don't have a rotating shaft but a semi-static pin. However, most shops prefer to see total runout because it basically implies how to do the inspect, i.e. with a runout gage. On the other hand I don't have or want more than one diameter on this part. I might want that even if it was a rotating shaft.
Seems like straightness on the single diameter would look simpler on the drawing, but again, total runout is preferred by the shop. So, what's the datum? Total runout needs a datum.
I suppose I could have datum targets at each end and create a datum A-B. What would that look like. I'm not sure if that would actually be harder for the shop to inspect than just an axial straightness.
Any thoughts.
I am undecided if I should callout out Total Runnout or simply straightness, and by straightness I mean the Axial type, i.e. straightness applied to the diameter callout not pointing at the surface. Picture(s) attached.
Every example of total runout I've seen shows at least two diameters on a shaft, the diameter that is controlled by the total runout and at least one other different approximately concentric diameter to use a datum. Sometimes there are two smaller diameters at each end (typically for bearings) that are used as datums to form a datum axis (Datum A-B for example. Pictures attached.
These are for rotating shafts and I don't have a rotating shaft but a semi-static pin. However, most shops prefer to see total runout because it basically implies how to do the inspect, i.e. with a runout gage. On the other hand I don't have or want more than one diameter on this part. I might want that even if it was a rotating shaft.
Seems like straightness on the single diameter would look simpler on the drawing, but again, total runout is preferred by the shop. So, what's the datum? Total runout needs a datum.
I suppose I could have datum targets at each end and create a datum A-B. What would that look like. I'm not sure if that would actually be harder for the shop to inspect than just an axial straightness.
Any thoughts.