303 Stainless steel is a slightly different alloy than the most common stainless, 304. It is supposed to be easier to machine, which means both that it wears out the tools more slowly and that the same techniques will give a smoother and prettier finish to 303 than 304.
But, how different does it feel to work with one versus the other? Would it be obvious to anybody, even someone inexperienced and untrained in machine tool work?
How motivated would you feel to hunt down 303 in the shapes and sizes you need, given that it is somewhat less common and less available, rather than using 304? How difficult would a job have to be so that you would order 303 rather than using 304 you already have on hand?
Not much difference between the two as far as machining…304 maybe has more rust resistance.
I think 304 was food grade SS, since we used that mostly for packaging equipment. 302 for frames and stuff and 316 for wear resistance.
I forget what the deal with 303 was…probably heat treat-ability or something, or braze-ability to brass.
There is defiantly a difference between 302 vs 316 as far as machining.
Another vote for not much differance. It is still high in chrome content so you will need really sharp high speed steel tools or carbide. If you use H.S.S. make sure you stop pushing the cutter/drill when it stops making chips. You will work harden the SS when the cutter rubs.
I have drilled wire edm start holes through 1 1/2 inch 420 stainless blocks with a 1/32 drill by following the “keep making chips” rule.
FWIW the differences are supposed to be: 304 is general purpose, 303 has added sulfur to make machining easier, 302 has higher carbon to increase strength, and 316 has added molebdynum to increase corrosion resistance (which cuts the strength in half).
The free machining description is for the guy cranking out production. There will be a noticable increase in the number of parts produced per hour if you use the alloy with better machinability. For a one off piece the differance is less noticable.
I specify a variety of parts, usually single items or small quantities but occasionally hundreds. I have always chosen stainless on the basis of its final application conditions but wondered if I should be considering machinability. Usually I use 304 or in the case of some chemical applications 316.