GD&T helpful link

[ctopher]

I came across this site by accident.
I thought I would share; it's one of the best descriptions of GD&T I have seen.
GD&T Link

ctopher, CSWP
SolidWorks '17
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[pmarc]

It is just a pitty that the author was not able to recognize that the "simple drawing" taken from Wiki contains ridiculously fundamental error.

 

[dtmbiz]

Stinkin' diameter symbol.. At first it appeared that somebody needs a checker, however further down this omission seems to be intentional

The Leader Arrow points to the hole feature. It has a Geometric Symbol, in this case, a Position Symbol. Given that this is a round hole, the tolerance could be a diameter, in which case we’d have a diameter symbol ahead of the tolerance. Instead, we just have a tolerance value, so this is a positional tolerance for the center of the hole.

 

[ctopher]

There are some small details, but overall a good learning tool.

ctopher, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

 

[pmarc]

Given that this is a round hole, the tolerance could be a diameter, in which case we’d have a diameter symbol ahead of the tolerance. Instead, we just have a tolerance value, so this is a positional tolerance for the center of the hole.

This makes things even worse. By saying this the author clearly admitted that there is nothing wrong with the callout.

 

[greenimi]

A couple of questions:

Is it correct:"....so this is a positional tolerance for the center of the hole. "?
Does the hole have a center or has an axis?
I think the circle (2D) has a center and the hole (3D) has an axis.

If no Ø is used, then maybe (just maybe) drafting is important....meaning two positional callouts would be better to be shown (both to the same DRF): one position drafted/drawn parallel to one side (vertical) and the other (geo. tol.) position drafted / drawn parallel to the other side (horizontal)

 

[dtmbiz]

Greenimi

Geometrically a circle has a center, however in the context of Y14.5 Positional Tolerancing the control applies to a 3D Feature Of Size.
(geometric circles have center points, cylindrical feature's have an axis)

For a cylindrical feature (round hole for "shop talk") would still be position of an axis.

In the absence of the diameter symbol preceding the tolerance the positional control would be up to anyone's guess.

Some might say it refereres to two perpendicular tolerance zones. Each zone 0.02 apart parallel planes located and oriented by the basic dimensions. (cartesian tolerance zone).
(If that was actually the case where the hole had two different tolerance values, then two separate controls (FCFs) are required)

Others might say it is a "boundary" as in location of a "slot" or a FOS with a MMC or LMC modifier.

I believe most knowledgable GD&T persons would simply believe the diameter symbol was inadvertently left out. (not an uncommon mistake)

According to this website's text, I do not believe it is possible to know what it is trying to "teach"