# Profile of a Line of a radius of 25mm basic dimension - Question

#### DWPOZE

##### Registered Visitor
We have a part that has profile of a line of a radius of 25mm basic dimension with a profile tolerance of 1mm. I understand that the radius must be 25mm +/- .05mm. If I measure the part and 25.03. Would the result .03 or would I double that to .06. Thanks for your help. I don't understand why you would double it.

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#### Colin

##### Quite Involved in Discussions
Re: Profile of a Line Question

If I understand your question correctly, you are measuring a radius so no, you don't double it, just take the dimension for what it is. Of course if you were measuring the radius as part of a circle you would need to double it.

#### Stijloor

Leader
Super Moderator
We have a part that has profile of a line of a radius of 25mm basic dimension with a profile tolerance of 1mm. I understand that the radius must be 25mm +/- .05mm. If I measure the part and 25.03. Would the result .03 or would I double that to .06. Thanks for your help. I don't understand why you would double it.
1 mm or 0.1 mm? Let's assume 0.1 mm. The profile tolerance zone is a 0.1 zone within which all elements of the profile must lie. The default allocation of the profile tolerance zone per ASME Y14.5 is "equally disposed about true profile." That means 0.05 up and 0.05 down from true profile. Not necessarily +/- as you call it. If the deviation from true profile is measured 25.03, then the measurement is correct.

Hope this helps.

#### DWPOZE

##### Registered Visitor
We deal with a lot of sheet metal parts that have a basic radius dimension and a profile tolerance. So on the part I mentioned above is out .03 would I report the profile as .03 or would I double it? Thanks

D

#### David DeLong

Profile is 0.1 mm (range) or 0.05 mm from basic profile. Since you measured and found it to be 25.03 which is 0.03 from the basic dimension, one would have to report 0.06. So, tolerance is 0.1 and actual is 0.06.

Remember, you divided the tolerance range by 2 and then measured. Now that you have measured it and found it 0.03 off true profile, you have to multiply it by 2 to get back to the tolerance.

#### Paul F. Jackson

##### Quite Involved in Discussions
David is correct.
If you are going to compare the deviation from true profile directly to the profile tolerance then you must reflect the amount of tolerance equally disposed about the true profile (in this case) needed to contain the deviation.

R 25.0 [profile|0.1|...] is 0.06 (+0.03)
Paul

#### Stijloor

Leader
Super Moderator
We have a part that has profile of a line of a radius of 25mm basic dimension with a profile tolerance of 1mm. I understand that the radius must be 25mm +/- .05mm. If I measure the part and 25.03. Would the result .03 or would I double that to .06. Thanks for your help. I don't understand why you would double it.
Can you share an actual drawing of the part? Or at least part of it?