True Position of coaxial diameters
True Position of coaxial diameters
(OP)
If I have a drawing with two coaxial diameters with no true position callout, what is the assumed true position, if any?
Is it located positionally by the size tolerance?
Thanks,
Is it located positionally by the size tolerance?
Thanks,





RE: True Position of coaxial diameters
Could you describ the part.....is it a shaft or block?
I you have ASME Y14.5M then check the Taylor Principle or comely known a Rule #1 - Where only a tolerance of size is specified, the limits of size of an individual feature prescribe the extent to which variations in it geometric form, as well as its size, are allowed.
If this is a shaft part....then I would make one hole a datum and apply runout to the other hole referencing the applied datum. Do not use TP on a shaft....your QA department will through a fit.
Best Regards,
Heckler
Sr. Mechanical Engineer
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RE: True Position of coaxial diameters
RE: True Position of coaxial diameters
Best Regards,
Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NIVIDA Quadro FX 1400
o
_`\(,_
(_)/ (_)
"Coming together is a beginning, staying together is progress, and working together is success." - Henry Ford
RE: True Position of coaxial diameters
I have a drawing of a stepped pin and the centerline runs through the entire part. The size tolerance on the smaller diameter is ±.010 and the true position tolerance is ±.022.
Just wanted to know if a tighter true position was already being held by default, then the ±.022.
Thanks,
RE: True Position of coaxial diameters
As I mentioned in my previous post......I would not use TP for this. I would make one diameter a datum and reference the other diameter to that datum via runout or total runout. The same would be true if you want to use TP one diameter would have to be a datum and the other diameter would be referenced to that datum.
A positional tolerance defines a zone within which the center, axis or cetner plane of a feature of size is permitted to vary from true (theoretically exact) position.
Circular Runout is a two dimensional, surface to an axis control. The tolerance is applied independently at each circular cross section. When applied to a surface constructed around a datum axis, circular runout will control cumulative variations of circularity and coaxiality. Unlike total runout , it doesn't control taper.
Total Runout is a three dimensional, surface to an axis control. Total runout provides a composite control of all surface elements. When applied to a surface constructed around a datum axis, total runout will control the cumulative variations of circularity, straightness, coaxiality, angularity, taper and variations in the surface.
Best Regards,
Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NIVIDA Quadro FX 1400
o
_`\(,_
(_)/ (_)
"Coming together is a beginning, staying together is progress, and working together is success." - Henry Ford
RE: True Position of coaxial diameters
RE: True Position of coaxial diameters
RE: True Position of coaxial diameters
Am I misinterpreting this section.
Without any true position, concentricity, etc, how much can the center axis of these two coaxial diamter (each with a size tolerance of ±.010) vary?
RE: True Position of coaxial diameters
Thanks,
RE: True Position of coaxial diameters
Best Regards,
Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NIVIDA Quadro FX 1400
o
_`\(,_
(_)/ (_)
"Coming together is a beginning, staying together is progress, and working together is success." - Henry Ford
RE: True Position of coaxial diameters
You stated previously that the positional tol was +/- .022.
I respectfully suggest that GD and T by Y14.5 does not recognize negative tolerances.
RE: True Position of coaxial diameters
Rule 1 (The Taylor Principle) applies to individual features only, not to the relationship between two features. If there are no GD&T controls, there is no relationship between the two diameters.
The axis of one cylinder should be the dateum, and that datum should be used to control the runout of the second cylinder.
Phil
RE: True Position of coaxial diameters
Without datums and GD&T... from an inspection point of view, one cylinder will be constrained and guaged, establishing the actual axis of the part, and the other cylinder's axis will have to fall within the second cylinder's size tolerance zone, with the established axis of the first cylinder as the axis of the size tolerance zone.
RE: True Position of coaxial diameters