Cylindricity

[ram1817]

I am so much confused with Cylindricity tolerence.
I have cylinder drawing Inside Dia : 8.00 + .004
And Cylinricity(inside dia) is : 0.006 in drawing.

Cylindricity must be less than size tolerence ?

If Actual measurement is : Max dia: 8.0056
Min dia: 7.9997

And Cylindricity is: 0.002
Is this acceptable ?

Please help me..

Thanks in advance

 

[SeasonLee]

Whenever Rule #1 applies to a cylindrical feature of size, an automatic indirect cylindricity control exists for its surface. Its cylindricity is automatically restricted to be equal to its size tolerance. For your case, the cylinder inside diameter is 8.00+0.004, so the maximum allowable cylindricity error on this part should be 0.004, however your drawing cylindricity callout 0.006 which is larger than the maximum allowable cylindricity error 0.004, therefore the cylindricity callout must be smaller than the maximum allowable cylindricity error 0.004.

Now, take a look at your actual measuring data, the max dia 8.0056 is larger the upper limit size 8.004 and the min dia 7.9997 is smaller than the lower limit size 8.000, all of them are out of tolerance, the actual (local) size must be within the maximum and minimum limits of the size dimension.

SeasonLee

 

[Belanger]

Is the specification for your cylinder 8.00 PLUS .004, or 8.00 PLUS/MINUS .004?

If it is ±, then the tolerance is actually a total of .008, making the cylindricity amount legal. (There is also an exception to the rule for non-rigid parts...)

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

http://www.gdtseminars.com