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# help, cylindricity

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## help, cylindricity

(OP)
when a cylinder has only (diameter) size tolerance specified, but no cylindricity tolerance callout, is there an implicit cylindricity which should be applied?
in another word, if a cylinder to be 1.000 +.002/-.000, is the cylindricity of .002 acceptable? or .001?
Replies continue below

### RE: help, cylindricity

A maximum size tolerance including cylindricity is implicate if the drawings states "conforms to ASME Y14.5M - 94. This is called "rule #1" in GD&T. In your case the maximum size would be 1.002. What this means to you is that your diameter must be able to go into the straight tube of ID 1.002.

Cylindricity is a combination of straightness, roundness and also size distortion and in your case can only be a maximum of  .001 but it does have to be shown on the drawing otherwise rule 1 applies.

If you drawing does not refer to the ASME standard, then there is only a size tolerance. That is it.

Dave D.
www.qmsi.ca

### RE: help, cylindricity

(OP)
first thanks.
the min dia is 1.000, the max, 1.002. so cylindricity .001 is the worst cylindricity it can be. otherwise, it is possible not meeting the diameter tolerance.
put my question in another way - is it true that there is no implicit requirement that when the cylindricity is not specified, it should be half the worst condition, in this case, .0005 ?

### RE: help, cylindricity

DHO, this is an area where ISO & ASME standards differ.

Please state to which standards you are working, this will help direct the responses.

KENAT, probably the least qualified checker you'll ever meet...

### RE: help, cylindricity

(OP)
thanks.
i have no idea about ISO standard. look through ASME Y14.5, it has nothing. but i remember that i heard, or was taught, etc, there is an implicit control or relationship if cylindricity not specified.
so, please tell me which ISO and what it says.
thanks again.

### RE: help, cylindricity

Look at section 2.7 'Limits of Size', especially 2.7.1.2 of ASME Y14.5M-1994 if this is the standard you work to.

I thought there'd been a similar question over on forum1103: Drafting Standards, GD&T & Tolerance Analysis recently but I don't see it now.

Questions on tolerance & GD&T may be better posted there anyway.

If I recall correctly it is ISO that say's there isn't an implicit control on form.

KENAT, probably the least qualified checker you'll ever meet...

### RE: help, cylindricity

If the size tolerance is 1.000 +.002 -.000, Rule #1 will control the maximum possible cylindricity error to .002, not .001.  If the cylinder's local diameter is at LMC, the cylinder could be bent by as much as .002 and still pass through the MMC boundary.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

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