I have gotten lost in those forums to the point I don't remember what the original topic is! Thanks! Glad you found it compelling. Who knows, maybe tapered surface total runout is the next evolution in poppet valve technology
If you suggest tilting according to the basic angle at inspection for getting the direction to run the indicator at, do you imply that the cone must be dimensioned by a basic angle to apply total runout to it? What if the cone's angle is directly toleranced and total runout is applied? Chances are high that some would do that. And if a cone is dimensioned by a basic angle one might as well define a profile of surface with reference to the datum axis to get exactly the same effect - a tolerance zone bounded between two coaxial cones that are also coaxial to the datum. The conclusion - don't use total runout on a cone.
I suppose if one were to directly tolerance the angle, you would have to do the inspection at multiple angles until the total runout was either measured in spec, or determined to be out of spec.... a very unfortunate inspection but possible As far as surface profile goes, you may have a case where the end diameters of the cone could have a much larger size variation than the allowable variation in the surface. A surface profile may needlessly restrict the "size" of the cone when only the total runout needs to be tightly controlled I hope I explained that well, if not, I could make another video about the difference
@GDandTNerd Yes, I guess the inspection of total runout at multiple angles when there is no basic angle is theoretically doable, but indeed very unfortunate, as you say. My opinion - it wouldn't make sense because such control is not likely anything that "simple" runout (each cross section separately) wouldn't do. Well, maybe it would add a limitation to the "straightness" of the cone outline (limiting curvature) as long as the indicator runs along a straight line. As for profile of a surface limiting the size of the end diameter of a cone, I don't think that is correct. I recall some mentions in Y14.5 of profile controlling "size" for cones but that is just bad wording. Profile of a surface doesn't limit the size of a cone because any size on a cone depends on the local length from the apex point and the profile zone has no way to limit that lengh. You are allowed to extend the tolerance zone as much as necessary because it is required to "cover" the entire actual feature (there's a Fundamental Rule that states this).
Ah, you're correct. I was imagining controlling the form with a basic angle and a basic diameter Fig 8-17 and 8-18 in the 2009 standard is probably what you're remembering, where the angle is basic and the diameter is directly toleranced I suppose in that case, while the method of control is slightly different between the total runout and surface profile, the allowable forms could be the same!
Lucky that forum post was only two pages. Some of those topics go on like Russian novels.
Solid argument btw.
I have gotten lost in those forums to the point I don't remember what the original topic is!
Thanks! Glad you found it compelling.
Who knows, maybe tapered surface total runout is the next evolution in poppet valve technology
If you suggest tilting according to the basic angle at inspection for getting the direction to run the indicator at, do you imply that the cone must be dimensioned by a basic angle to apply total runout to it? What if the cone's angle is
directly toleranced and total runout is applied? Chances are high that some would do that. And if a cone is dimensioned by a basic angle one might as well define a profile of surface with reference to the datum axis to get exactly the same effect - a tolerance zone bounded between two
coaxial cones that are also coaxial to the datum. The conclusion - don't use total runout on a cone.
I suppose if one were to directly tolerance the angle, you would have to do the inspection at multiple angles until the total runout was either measured in spec, or determined to be out of spec.... a very unfortunate inspection but possible
As far as surface profile goes, you may have a case where the end diameters of the cone could have a much larger size variation than the allowable variation in the surface. A surface profile may needlessly restrict the "size" of the cone when only the total runout needs to be tightly controlled
I hope I explained that well, if not, I could make another video about the difference
@GDandTNerd
Yes, I guess the inspection of total runout at multiple angles when there is no basic angle is theoretically doable, but indeed very unfortunate, as you say. My opinion - it wouldn't make sense because such control is not likely anything that "simple" runout (each cross section separately) wouldn't do. Well, maybe it would add a limitation to the "straightness" of the cone outline (limiting curvature) as long as the indicator runs along a straight line.
As for profile of a surface limiting the size of the end diameter of a cone, I don't think that is correct. I recall some mentions in Y14.5 of profile controlling "size" for cones but that is just bad wording. Profile of a surface doesn't limit the size of a cone because any size on a cone depends on the local length from the apex point and the profile zone has no way to limit that lengh. You are allowed to extend the tolerance zone as much as necessary because it is required to "cover" the entire actual feature (there's a Fundamental Rule that states this).
Ah, you're correct. I was imagining controlling the form with a basic angle and a basic diameter
Fig 8-17 and 8-18 in the 2009 standard is probably what you're remembering, where the angle is basic and the diameter is directly toleranced
I suppose in that case, while the method of control is slightly different between the total runout and surface profile, the allowable forms could be the same!