I refer to ISO 2768 from time-to-time.
I seem to recall by their own admission those tolerances might generally be attainable in a German machine shop staffed with old world craftsman.
To me 2768's value is quickly estimating the tolerance level that can be expected "for free" to benefit Design for Manufacturability.
Nowadays a sizeable part that could be produced completely on a CNC machine automatically might achieve ± .0005" or better.
Like MintJulep said, what your parts NEED may well be something completely different.
At the very least, some components may need a unidirectional tolerance (+0.000/-.002") in place of the ± in ISO 2768.
Tolerances for Housing Bores for ball/roller bearings come to mind as unidirectional, right in the Bearing manufacturers catalogs.
Some of our US suppliers can't think in those terms, so we have had to revise our detail drawings into ±.
The answer to the original question is there is no similar standard on imperial dimensions for most products.
The only one I know of is H35-2, a specification for aluminum wrought, rolled, and extruded forms. Even that says - call your supplier if you wish to avoid surprises. Likewise AGMA (American Gear Manufacturers Association) has their own standard for what their members consider normal variations. And somewhere there is a standard for typical drilled holes, though in Machinery's Handbook it says their values came from a test of hundreds of holes drilled into cast iron, so any other material is likely to have a different range.
Other than that I have no recall of any fabrication tolerance standards that cover dimension extent vs. variation allowance.
I am a USA engineer, and I second what Dave said.
ISO does have standards for hole size and shaft size.
During after world War 2 most of internal standards were developed by ford, GM , Boeing, and other major first tier companies.
From extensive testing and trial and error.
OEM manufactures of components have the recommended form and fits. For precision assembly.
And it takes years and years of experience
For me the ISO tolerances are useful to quickly identify and then define the tolerances for dimensions of components to achieve the desired fit,
but it's still on the designer to determine what is needed.
Even for a fairly specific category, like ball bearing housing fits, the "right answer" might be line-to-line, interference, or loose/clearance.
