Which is most prefereble Dimensions method? 1

[RathodAsit]

Dear All!,

As we are making GI Sheet metal and Busbars Drawings for Electro Mechanical Products, Please let me know which is the best method to call the dimensions,1.) Ordintate Dimensions(Pick two faces and give X and Y dimensions) 2. EDGE to Hole and then Hole to Hole, Tolerance used in parts are ISO2768-M.

Thanks in advance

Best Regards
Asit Rathod

 

[powerhound]

Yes. Things always work fine...until they don't. Just go the the thread titled "Datum" for a perfect example of what I'm talking about.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

 

[randomdrafter]

^ That type of issues are always considered and there are strict quality process. i am talking about simple parts which are used repeatedly for many years. Any new design will be taken care with all due diligence.

 

[3DDave]

"Only when there is tighter tolerance required we can change the scheme and go with GD&T."

As a practical manner, it's only when tolerances are nearly the same as acceptable variation that FCFs are valuable. When the variation is a small portion of the available tolerance there's little value in making the effort to precisely describe the factors governing inspection.

One might suggest that it's always the case that a precise description is required, even when the tolerances are large, but if an organization has control of the production process and the design won't be floated to outside organizations, then there's no reason to not take advantage of the existing controls. For example, in four-color printing the tolerances involved put most metal work to shame, but the equipment and the setup is understood and your newspaper, magazine, or t-shirt come out OK.

OTOH, if production capability is on the edge of design requirements (either direct limits or 3 or 6 sigma boundary) then the increased precision of the description can help separate out the usable parts from those not usable.