I like and prefer .045 to .050 thickness titanium sheets for my clips personally. Mostly this is due to the nature of my work. What I find working on so many production folders is that if I use a clip material thicker than .050 thickness it can cause me to run into situations where the factory screws used in the original clip are not long enough to grab and pull it down tight when I replace it. Since many companies, particularly the ones contracting out with Japan, China, and Taiwan as well as other countries, use proprietary screws that are odd sizes compared to what I stock I've learned that many times its best to stick with what is used by the factory for the best fit. On some Spyderco models the clips are .050 and the screws barely catch as they come as one example so if I am over that thickness by just a tiny amount its sometimes enough to make it such that I have to recess a screw down or something to make it work with thicker clips. In my efforts to keep it clean and easy I simply figure its better to be slightly under than over for thickness so I've found .045 works universally well for me for all things including my custom low rider clips. I still keep some thicker sheets here to do some beef cake clips for but most of the time those are limited to the ones I can easily replace screws on so most always they are USA made or if foreign made they are made using standard size 2-56 screws or something else I can easily find.
I'm sure if I looked hard enough I could find some of the metric ones but the trouble is it isn't like the screws are stamped to tell you what size they are. In the end its easier to just stick with doing them in advance knowing the material you are using will work for the original hardware. So, if you are planning to replace original factory clips I'd suggest sticking with something at or below the thickness of the clip you are replacing. If custom, well heck use .050 or thicker. I've done some of .070 for people carrying super sized knives and they come out pretty dang stout let me tell you.
STR