Unilateral Tolerance

[gearing_guy]

I have a print with a dimension of 98,5 and it's tolerance is -0,3 and -0,2. I understand the ideas behind double minus or plus tolerancing. I do not completely agree with it but that is not the point here. Normally I am always used to seeing the max size on top and the min size on the bottom. This is not the case here. I am leaning towards this being a typo I will be checking with my customer on Tuesday, but I was wondering if anyone else has ever seen something toleranced like this. More than just the min size being on top another clue that leads me to thinking this is a typo is the other lengths on this part are toleranced +0/-0,5. The 98,5 dim is the OAL which does not appear to be critical.


Thank you in advance.


Bill

 

[mkcski]

gearing_guy:

Yes, typicality the nominal dimensions is between the high and low size. Your example looks like an ISO tolerance "ranges" to me, which "allows" this type of tolerating. In any case, I would not casually assume anything. Contact your customer to confirm your interpretation

Certified Sr. GD&T Professional

 

[juergenwt]

Converted from 3 7/8" to metric ISO tol..

 

[drawoh]

gearing_guy,

I regard double plus and double minus tolerancing to be a good idea. It shows off the required fabrication dimensions, and it shows off the as modeled size. I would assume that your dimension is an external feature, and that there is a hole dimensioned 98.5+0.2/0, or something like that.

Putting the smaller size on top is weird, and I agree with mkcski, that you should your customer and verify what they want.

--
JHG

 

[gearing_guy]

Thanks for your responses. I would never assume anything especially with this customer. The dimension is an Overall length. I was just looking if there is a standard way it should be written. I looked through specs and could not find anything when that specifically said when using double plus or minus tolerancing it should go high to low. I am trying to get an answer on this today.


thanks again