Mkawa what sort of tooling would you suggest for a countersink bit for working with this stuff?
If I can make this work would anyone else be interested in having either the top or bottom plates countersunk for use with flat head screws?
it's unalloyed, so you could use HSS if you wanted and you'd be able to make it through at least a few plates before you noticed the bit dulling. full tungsten carbide or cobalt HSS alloys will increase duty cycle, with the former probably being more effective. i would avoid TiN or TiAN coatings and just get bright (uncoated) bits and use a very slow feed rate and lots of coolant. other than that, all you really need is a good square drill press, a jig with solid hold-down to keep everything stable and control depth stoppage. wear resistance is really key in the tool, because the anodized plates will have a non-trivial skin of very hard titanium dioxide that you need to make a clean cut through at very low speed so that you don't further oxidize the part, and then a bunch of relatively hard (HRB60-ish) titan to drill through.
one thing to emphasize is coolant, coolant and more coolant. titanium oxidizes almost instantly when exposed to air. the depth of oxidization depends on heat and some other junk. if the depth of oxidization is large enough, you get discoloration (which is why we only get indexed colors from our anodizer -- there is no dye, yah? just the titanium dioxide surface density causing diffraction at different wavelengths depending on depth). the upshot is that this becomes much much less of a problem if you don't expose the titanium you're cutting to air.
if you happen to have a small nitrogen generator around, i guess that could help too, but good old cutting oil is a lot more readily available and probably about as effective.
note that avoiding tin and tian and lowering feedrates is also important because of slagging and welding. titanium has a relatively low annealing point; it's higher than aluminum (which is painfully low) but lower than steel. most tools are made to cut steel, and yet are made of a steel alloy. cutting hardened steel with less hardened steel is going to destroy your edges pretty quickly, so manufacturers plate bits with stuff and use the steel inner as structural reinforcement and heatsinking, so you can use high feed rates until the coating burns off or the bit breaks and then you toss the thing and it gets remelted and circle of life etc. to make deep cuts into stuff that's hard, you just need a hard bit and to cut slowly, not a hard plating that will immediately burn off and slag everything.
