Tertiary Modifier is B(MMC)- C(MMC)?

[rvenzon]

I've come across a feature control frame for positional tolerance, where the tertiary modififier shows B(MMC)- C(MMC).

What does this imply? If more info is needed, please specify what.

Thanks!

 

[ringman1]

drawoh,

On one of your posts you suggest that a line may be used for clocking. Is that possible? I thought clocking (orientation) properly expressed should be to a point.

 

[PeterStock]

"On one of your posts you suggest that a line may be used for clocking. Is that possible? I thought clocking (orientation) properly expressed should be to a point. "

Just pick a point on the line.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[drawoh]

On one of your posts you suggest that a line may be used for clocking. Is that possible? I thought clocking (orientation) properly expressed should be to a point.

I was speculating that the FCF could conceivably be valid. I was not saying it is a good idea.

How about this. Datum_A is the bottom face. Datum_B is a point at one end. Datums_C and_D are holes, and are called up as a compound datum. Holes_C and_D would be picked up in the fixture by diamond pins which would restrict side to side movement and rotation, but allow wiggling to and from datum_B.

Another possibility is that datum_A is the bottom, datum_B is a radius at one end, and datums_C and_D are holes. Datum_B locates the part in X and Y. Compound datum_C-D is a pair of diamond pins on a slider such that the two holes are located to a specified angle.

I think these are valid applications of datums as per ASME Y14.5M-1994, and I think this is horrible practise.

JHG