Issues with calling out "STK/STOCK" is that sometimes it's bad business to tell people how to make parts, who are in the business of making parts. Unless it is critical to the design of your part, such as grain direction or other structural considerations, just tell them the finished size. If you call out "STK" as a way to indicate an unimportant REFERENCE dimension, that's one thing. To call out ".250 STK" and expect them to hold whatever your applicable tolerance is, say +/- .010, you'll be disappointed. Most I've encountered take "STK" to mean "Start with that size stock and clean it up. Your final dimension is whatever is left, that's it." which means they treat "STK" essentially as "MAX". Not saying it's right. Saying what I've seen in various manufacturers. If the dimension has a tolerance to it, leave off the "STK/STOCK", IMO.
Here, we treat it as a REF dimension (that rule was established before I came here and I have had to reason to challenge it).
The popularity of dovetail vices has rendered "STK" dimensions a PITA for anyone hired to make parts. Yes, the part can be made from 1-1/2" thk bar stock, for example, but they'd rather start with 1-5/8 or 1-3/4 so they can machine a dovetail into it and cut on all 5 remaining sides while it's in a dovetail vice.
I also wouldn't rely on the flatness, straightness, roughness tolerances of stock material. Depending on your supplier, you may or may not be getting material in such condition. Yes, it might have started that way when it was fresh off the rollers from the mill/foundry, but you don't know what you're going to be delivered. It's sometimes cheaper to just get something 1/8 or 1/4" thicker and machine it down than to pay a higher price for stress-relieved flat stock at the 'finish' thickness. Depends on the part of course.
Long story short- there's a lot of variables at play that you don't see if you're not familiar with buying material and making parts from it. IMO it's best, as a designer, not to create expectations of what stock material to use unless it's critical to your design. You're not doing anyone any favor by suggesting they use 1" x 1/2" bar stock. They will look at your part and decide what stock to start with. They likely know much better than you do, based upon their supply chain and in-house capabilities.
*edit* Fixed a couple grammatical issues
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NX8.0, Solidworks 2014, AutoCAD, Enovia V5