I have a Spyderco knife that has a 3036 SS blade. I looked up the tinsile strength of it one time after I broke the tip. IIRC it was pretty hard, but brittle. I looked it up using the Rockwell scale, but after a few minutes of searching today, I couldn't find any data, other than some steak knife company.
Hard, but brittle. I wouldn't use it anywhere critical.
Most commercial grades of stainless will be either 303 (for machiability), 304 (for standard sheetmetal work) or the more exotic 316 and 316L (lower carbon). Hardware is typically 303. I would not use S.S. fasteners for your center pin application - in general, stainless of any grade will be "softer" than a comparible carbon steel fastener; more prone to bend and distort. Additionally, S.S. fasteners have a nasty habit of gauling - you should definately use anti-sieze and be careful if while torquing them down or you'll tear the head right off the fastener.