Double up with tolerances

• 07-31-2013, 02:07 AM
Epleskrell
Double up with tolerances
Hi all,

I am currently working on some drawings and we are in the process of setting up the tolerances. Now a co-worker has during my vacation done a preliminary suggestion of the geometric tolerance. As I am now looking through this some questions arise, and I hope I could get some input on this.

The question at hand is regarding double tolerances. And if in these cases one is making the other one obsolete.

Case one;

[ATTACH=CONFIG]695[/ATTACH]

In this case, would not the total runout tolerance be obsolete when the profile of the surface is kept that tight? Or can they be used together and if so, how does that work?

Case two;

[ATTACH=CONFIG]696[/ATTACH]

In this case, will the flatness be needed when you state that perpendicularity? Will not the perpendicularity tolerance demand that the surface as a whole is within that 0.1 limitation? If not how does these to play together?

Thanks for all the help, and thanks for having such a great community. Just discovered these forums and I am most happy to be here.

Kind regards.
• 07-31-2013, 07:06 AM
Kelly Bramble
Case one:

First, the total runout tolerance would be apprpriate for a tapered cylindrical application. Circular runout might be a better surface to datum axis A control in that only individual circular elements would be measured relative to the specified datum axis A. Total runout specification would require all surface elements to be measured in a single setup (dial indicator oriented at specified angle to datum axis and then zeroed and part rotated).

If circular runout was applied in this application then the circular runout would control the form and location to 0,1 of each individual circular element relative to datum A. The Profile of Surface tolerance 0,05 is then used as a refinement of form limiting the total surface variations relative to the surface itself. The profile tolerance would be a refinement of the surface form where the circular runout would control the form, orientation and location of EACH individual surface element relative to datum A.

Case 2:

The flatness tolerance is meaningless as the perpendicularity tolerance will control the total surface variations (Flatness) to 0,1. Flatness should only be used as a refinement of form and is always hieratically contained within tolerance boundaries defined by orientation tolerances.
• 08-01-2013, 01:59 AM
Epleskrell
Thanks allot for the complementary answers Kelly! Really helpful :D
• 08-17-2013, 11:44 AM
Belanger
This is a good place for me to get your input Kelly -- I have always maintained that total runout can be used on a cone (if desired) even though the standard doesn't ever show such an example. The catch is that the angle of taper MUST be given as a basic dimension; the dial indicator could then be rigged so that it rides along on that prescribed angle.
Thus, a perfect cone (form, orientation, location, but not necessarily size) would register zero for total runout. Your thoughts?
• 08-17-2013, 03:00 PM
Kelly Bramble
ASME Y14.5-2009, see 9.4.2 and I quote.

“See Fig. 9-3 When verifying total runout, the indicator is fixed in orientation normal to and translates along the tolerance surface.”

Specifically “normal to” would mean perpendicular… So, though there is not an explicit illustration of total runout on a tapered or profile surface, I do believe the standard does in fact allow for this interpretation and application.

For example:

[ATTACH=CONFIG]702[/ATTACH]
• 08-17-2013, 03:05 PM
Kelly Bramble
Moreover, by extension one could apply total runout to a profile as well though the physical setup might be challenging for open setup folks.

See ASME Y14.5-2009, Figure 9-5. The circular runout specified on the profile diameter is 0,08 relative primary datum C and secondary datum D could be changed to total runout and measurements taken with the proper setup. That is normal to the profile as the dial indicator translates along the profile.