Inspection symbols with GD&T 2

[MattBD]

On a part drawing, I have an outside profile constructed of multiple blended radii. The part has a hub extending from the bottom that I am using to set two datums: the bottom (A) and the diameter (B) of the hub. There is a hole perpendicular to those two that is datum C.

I have positioned the centers of the radii with basic dimensions from the center of the hub. The radii are also called out as basic, with a .010" profile tolerance all around the outer surface of the part (rel. to A and C).

I need to place inspection symbols on this drawing. With regard to the outside profile, should the feature frame indicating the profile tolerance be the only thing with a symbol on it? (You can't actually inspect a basic dimension, right? That's only a theoretical point/line/plane in space.)

Thanks,
Matt

 

[MattBD]

I hate replying to myself, but while I'm at it:

I have a similar question for positioning a hole. I want to inspect both the hole size and true position called out on the drawing. Would I label both of those with an inspection symbol?

Is there an applicable standard for including such symbols?

Thanks again,
Matt

 

[ewh]

I don't think you will find any information regarding inspection symbols in Y14.5. Its purpose is to standardize the definition of something, not how to inspect it. This said, inspection is definitely something to consider when using GD&T. Most places where I have worked separate definition documentation from inspection documentation. They may mark up a drawing copy to specify what needs to be inspected in what order, but it is seldom, if ever on the original drawing itself.

I know I didn't answer any of your questions. Sorry about that!
1) Place it near the FCB
2) Yes. As you said, you can't very well inspect the basic dimensions
3) Place one near the hole callout to cover the size tolerance and another near the FCB to cover the location

I do not work in inspection, but from what I have seen, this is how they would approach it.

 

[KENAT]

Like ewh I wouldn't normally put inspection on the drawing. Same as I wouldn't normally put manufacturing instructions on the drawing (ASME Y14.5 para 1.4e). In fact if you count inspection as part of the manufacturing process then you probably shouldn't put it on the formal drawing.

To me this should go somewhere like a quality plan or inspection procedure. In this document you could include an annotated drawing. As such you can use pretty much whatever symbology you like, as long as it’s clear, unambiguous and defined somewhere. I’d talk to your inspection, or if out sourcing, the vendors inspection to see how they’d like it done.

Inspection plans I’ve seen often have a table with all the relevant dimensions listed with a ‘grid reference’ of where on the drawing they are. The table has a column to fill in the actual measurements.

 

[PSE]

If possible, inspection will (or at least should) try to use the datums from the drawing for orienting and referencing the part. You can tolerance the relations of the datums to one another if this would help.

Note: In no way do I consider myself a GD&T expert.

Regards,

 

[dingy2]

Well you have me baffled on this one!!

I have been in the Quality game for over 40 years and placing some sort of inspection symbols in place of GD & T blows my mind.

If one is performing a complete layout of the part on CMM, the Operator would number each dimension with a corresponding actual with the exception of basic dimensions. The "actual" on a basic dimension is the theoretical dimension.

If one is developing a Control Plan (some call it Inspection Plan) for ongoing inspection or control on the shop floor, we would still call a position tolerance with an appropriate gauge with the shop floor Operator knowing that each pin must be staked in each hole. If it is a profile tolerance, once could select areas on the surface and develop a variable reading gauge.

I would never replace a GD & T symbol with some sort of inspection symbol. I know that a lot of shop floor people do not know what the symbols mean but your company should have Quality Engineering people who should interrept the symbols and develop appropriate inspection methods.

Dave D.

http://www.qmsi.ca

 

[ctopher]

I agree Dave.

Chris
SolidWorks 06 5.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 01-18-07)

 

[JohnNabors]

Another vote for Dave.

John Nabors

Never try to teach a pig to sing. It wastes your time and annoys the pig.