How to use profile of surface feature control frame to control max. protrusion?

[jassco]

I have a feature size of a block. I need to control distance from end of the block to a datum "A". How do I use profile of surface FCF to control max. distance to the datum?

 

[3DDave]

Unilateral profile tolerance where the value following the unequally disposed symbol would be 0.

The question is, when you say "MAX" do you want to allow -INFINITY as the limit?

 

[jassco]

I can't do that as I don't care how small this dimension is. I just want to control this maximum dimension.

This dimension must be < = 26.

Basically, I am asking what is equivalent to 26 MAX. using GD&T feature control frame.

 

[3DDave]

So, make the profile of surface tolerance [1000 (U) 0] or any other value that is large enough.

Feature Control Frames (not GD&T) and geometric characteristic symbols define the range of variation from some nominal condition (not always a fixed boundary, e.g. circularity) and "MAX" isn't a range. Unlike diameter, there isn't even the possibility in this case of noting that 0.00 is the natural barrier to some "MAX" diameter for a hole or a pin.

 

[CheckerHater]

With MAX dimension the other limit is ZERO, not INFINITY.

So the unilateral tolerance cannot be larger than 26.

Question: should it really be MAX?

 

[3DDave]

Negative infinity. You have a barrier measured from one place and it's acceptable to be as far from that as possible.

 

[mfgenggear]

OP
You can't

 

[Burunduk]

Profile would control both MAX and MIN.
Since you say you care only about MAX, do you have some other control for the MIN?

BTW, it should be 50+/-0.25. No trailing zeros for metric dimensions.

 

[jassco]

No, I don't have a control for the MIN. It can be as small as "zero".

My issue with dimension 26 MAX. is that there are a lot of center lines. It is not clear which center line this dimension is associated with.

 

[mfgenggear]

OP
That is why I said you can't.
There is a missing detail or datum where the centerline is derived from. The drawing is incomplete.
The centerline is not drawn on center.
And is projected from where?

 

[3DDave]

Make the profile of surface tolerance [1000 (U) 0] or any other value that is large enough.

 

[jassco]

Yes. It is derived from another feature in the assembly. Center line of this feature is coincident with centerlines of many other features. That is why 26 MAX. is no good. Sadly, there is no GD&T equivalent to 26 MAX.

 

[3DDave]

Make the profile of surface tolerance [1000 (U) 0] or any other value that is large enough.

Enjoy the ignore button.

 

[jassco]

Thanks, 3DDave! But, if I use a profile tolerance of [1000 (U) 0], I'll have to inspect both USL (upper specification limit) and LSL (lower specification limit). I want to inspect USL only. How do I nullify this LSL?

 

[Garland23]

Write a note. There is no "GD&T" solution for your dilemma.

 

[mfgenggear]

Op
What many machinist freak out is when is a max. They try to make as close as possible to max dim. I have struggled with that as well.
Truth any dim. Under the 26 max stands on its own. And is acceptable. No other tolerances required.
A clarification note would be helpfull to alieve questions.