Profile tolerance vs linear tolerance - (GD&T newbie)

[Odiemena]

I'm obviously very new to GD&T and have questions regarding linear tolerancing vs profile tolerance. I have a customer who has a print that has different linear tolerances (depending on length. The part is a casting). Based on length, the linear tolerance is as follows:


Length Tolerance
0-25mm ±0.25mm
25-50mm ±0.33mm
50-76mm ±0.41mm
76-152mm ±0.64mm
over 152mm ±0.76mm

The print is calling out a profile tolerance of -0.3mm/+0.7mm. The part has overall dimensions in the 76-152 mm range. Is there any conflict between the two? I am assuming there is as my linear tolerance allows me to be ±0.64 mm but am not sure how the profile tolerance comes into play. Thanks in advance for your help!

 

[drawoh]

Odiemena,

I would assume that the more accurate tolerance controls the feature. In other words, your part should conform to each and every tolerance called up on your drawing.

JHG

 

[pmarc]

Odiemena,
The answer depends on what the print is really showing = how profile tolerance is actually applied. Is there any chance we could see the drawing?

 

[CheckerHater]

Odiemena,

I assume your tabulated tolerances are placed somewhere on or near title block and represent “general tolerances” or “tolerances, unless otherwise specified”.
Normally they only apply to dimensions without direct tolerances or geometric requirements.
Any other tolerance values or GD&T symbolic will override your “title block tolerances” for feature they are applied to.

Like pmarc mentioned, it is better to look at the drawing to be absolutely sure.

 

[pmarc]

CH,
If profile tolerance is applied to top surface of block's height and that height is controlled by simple size dimension then both tolerances may be valid since total amount of profile tolerance (1.0) is a refinement of size tolerance (1.28). That is why I wanted to see a picture.

 

[CheckerHater]

If profile tolerance is applied to top surface of block's height and that height is controlled by simple size dimension then both tolerances may be valid

If I understood correctly, the print specifies unequally disposed tolerance zone, which, according to the standard, is applied to basic profile.
I doubt you can create basic profile using “simple size” dimension.
I hope now we both agree that it may be beneficial to look at actual drawing.

 

[pmarc]

Correct, CH.
I goofed this time.

 

[Odiemena]

Thanks for all the help guys! Here is the print for the part in question:

http://www.flickr.com/photos/29668265@N02/7349382502/in/photostream

 

[Odiemena]

Here it is again. It failed to upload correctly in my last post

 

[SeasonLee]

Odiemena

Note 16 means Bilateral Unequal Distribution on the profile tolerance.

The profile general callout is |Porfile|1|X|Y|Z| and the tolerance 1 is divided into 0.3 and 0.7, where 0.7 is always on the added material side.

Take shaft Ø15 (external feature) as an example, the max dia=Ø16.4(0.7x2 plus 15), the min dia=Ø14.4. For an external feature , the added material is on the outward of the true profile.

Take hole Ø15 (internal feature) as an example, the max dia=Ø15.6(0.3x2 plus 15), the min dia=Ø13.6.
For an internal feature, the added material is on the inward of the true profile.

Hope this help

SeasonLee

 

[pmarc]

On the print, as it is now, note #15 adds no value. There is not a single directly toleranced dimension to which these tolerances might refer.

Two additional comments:
1. In my opinion note #16 should contain a statement like "UNLESS OTHERWISE SPECIFIED..." at its very beginning since there is another profile tolerance on the print - |prof|0.51|Z|A| - and it is not clear whether both profile tolerances, as stated in #16 and 0.51 one, apply to the surface described by basic R127 dimension or just 0.51.

2. On section view C-C positional tolerance at LMC is applied to a feature described by basic dimension. This is illegal callout. Either 16.51 dimension shall be directly toleranced (and then the general tolerance +/-0.25 from note #15 could apply) or positional tolerance shall be switched to appropriate profile of surface control.

 

[CheckerHater]

Odiemena, you are in good hands