Goodness....all of this talk of TPI for metric threads make my head hurt
You don't have a 32 TPI or a 28 TPI die nut..... as these would produce
25.4 divided by 32 [TPI] = 0.793 mm pitch
25.4 divided by 28 [TPI] = 0.907 mm pitch
So..... from the words of experience by 'bogstandard'.....[translated to OZ].....
1) don't throw them boith over the balcony just yet
2) console yourself with a small glass [or two] of good Australian wine
3) consider your options/plans & lets start with the tap
4) OK....set your vernier calliper [with or without a TV screen] between two thread points [crests of the thread form]....
5) if you use the TV screen version please set it to the METRIC nomination
6) if you see a numeral 0.8.........you now know you have an M5 x 0.8 pitch threadform
7) if you see a numeral 0.5.........you now know you have an M5 x 0.5 pitch threadform
Please re-read point 5) ....if you don't follow the directions......you will see numbers of 0.031496062 or 0.019685039....which are small bits of inches ["] & only confuse everyone further
repeat step 2).....
The only acceptable method of determining the pitch of your M5 die nut is to cut a thread on a section of 5.0 mm diameter bar stock......brass would be very good as it does not require any cutting agent...or coolant
9) ....repeat steps 4) 5) 6) & 7)
10) repeat step 2) or
So now you have the clear physical evidence of what the die nut & the tap produce
11) repeat step 10)
Telephone or call at your local engineering supplier & ask the costs for an M5 x ? pitch die nut in HSS
12) repeat step 11) as the cost will be expensive.....
13) remember you are intending to cut stainless steel material material with say 620 MPa strength so HSS is the only real option
14) in OZ...we have a product called TREFELEX ....like a green slime
....the best cutting agent for carbon & stainless steel grades...[for drilling & tapping purposes]