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GD & T Question

BioActive1142

Plastic
Joined
Nov 21, 2023
Can anyone explain the highlighted section please. We have a couple of different opinions here at the shop. Thanks!!
 

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I think someone should put the bottle down.

If they reject it they could tell me how any why it failed.
 
I'll give it a shot.

True position of 3 when the hole is MMC and the OD is MMC. So you gain on the hole being bigger than low limit and you gain when the OD is not at high limit.
Technically I thing that 73.73 dimension should be boxed.

The TP of 1.5 may be the "in line" of the holes to each other.

Regardless, that's pretty wide open. You could probably make a good one freehand on a drill press.
 
I'll second yoke. Engineer/Drafter is going too fast and the checker, if he exists, is asleep at his desk.
 
I'll give it a shot.

True position of 3 when the hole is MMC and the OD is MMC. So you gain on the hole being bigger than low limit and you gain when the OD is not at high limit.
Technically I thing that 73.73 dimension should be boxed.

The TP of 1.5 may be the "in line" of the holes to each other.

Regardless, that's pretty wide open. You could probably make a good one freehand on a drill press.
Right, the 73.73 dim should be boxed.

If you cared about the two holes being in line with each other, you would either datum one of the holes and tolerance the other one to it or you would use the 'continuous feature' call out.

Either way, it's sloppy work. Either give them sloppy work in return or send it back for clarification.
 
We don't have the entire drawing. I've often seen a note along the lines of "Untoleranced dimensions are basic." I use boxes per the standard, but does the drawing have a note like that somewhere?
 
I'll give it a shot.

True position of 3 when the hole is MMC and the OD is MMC. So you gain on the hole being bigger than low limit and you gain when the OD is not at high limit.
Technically I thing that 73.73 dimension should be boxed.

The TP of 1.5 may be the "in line" of the holes to each other.

Regardless, that's pretty wide open. You could probably make a good one freehand on a drill press.
I agree this is the intent and I'll add a few things.

First, if the ref dims regarding -A- and -B- datums aren't pinned down elsewhere in the drawing, a clarification is needed FOR SURE. Second, you also get bonus tolerance on B.

Right, the 73.73 dim should be boxed.

If you cared about the two holes being in line with each other, you would either datum one of the holes and tolerance the other one to it or you would use the 'continuous feature' call out.

Either way, it's sloppy work. Either give them sloppy work in return or send it back for clarification.
I agree with paragraphs 1 and 2. Para 3 is surely tounge-in-cheek since this is never a good work around for a poor drawing.

The hole feature callout 4.8-B is curious. Is B the tolerance, either tabulated on the drawing or in customer engineering specs? Either way I hate stuff like this on a drawing.

The feature control frame perpendicular to -C- just floating around by the right view is not the way to do things for two reasons. I believe the intent is to apply to -A- so it should be attached to -A-. In addition it is circular in nature. The hole feature should be perpendicular to the datum, not the other way round.

Drawings like this give GD&T an undeserved bad name.
 
It looks like they used a multiple single segment positional tolerance by mistake and should have used a composite positional tolerance with just one of the positional tolerance symbols in the left hand of the feature control frame.
They could have used the notch feature as datum C to lock down the rotation.
Yes, that perpendicularity control is floating out in space but I think it's intended to keep the notch feature perpendicular to the pin holes.
Lastly, datum B should not be referenced at MMB because it's just a surface, not a feature of size.
 








 
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