We will be using a 1/4-20, 5/16-18, or a 3/8-16 tap (we aren't sure yet because the job is still in the works). The catch here is that we can only passivate the surface of the stainless from were we work with a handheld device - the parts are about 17ft long and we have already determined that dipping these in passivation tanks would place us out of budget. That said, how can we use either one of these thread diameters (approx 5/8" of thread depth) without the use of lubricants on 304 stainless steel? (we are allowed to have an additional 3/4" of hole depth clearance, but cannot break thru.) The thought of not using tapping oil screams nightmare, but then again I've never tried anything like this.

I have tossed around the idea of using some exotic taps, but my knowledge of taps isn't that extensive. Would this help at all? What types?

Thanks!!!