lucas01230 wrote:
How else can you find out if the stainless 400 is indeed stainless and not common steel.
Starting out; you'll need to get them scanned. In time (and I do honestly mean eventually) you'll learn to recognise stainless steel and other stainless classes by sight clues.
How it reflects light, colours that are refracted, etc.
Some use various grinding wheels (many high volume fast paced yards do as well) and have memorized various spark types from them. The colour of the sparks, the shape, etc. For me, I've just gotten to the point where i've gotten familiar enough with the majority of what I deal with to know 90 some ought percent of the time.
Unless I have a massive (hundreds of pounds) volume of the same thing, I use two methods together personally for anything I doubt off hand.
First: I deeply gouge and file a clean spot dead centre of the piece. If it's still the same finish as the surface (matt vs gloss vs reflective etc) I move on to the next step. If not, into the clean sheet steel pile it goes. Not worth continuing.
Second: compare the colour reflections and refractions under fluorescent tube bulbs vrs LED bulbs of the clean surface and the filed area. And make a determination based on the differences.
When in /real/ doubt, into the clean sheet pile it goes.