The repondent said "Titanium" not "Titanium alloys". The only mpc maker I know of that employs only a "Titanium compound" vis Titanium Nitride is Houser Mouthpieces of Norristown PA http://www,housermouthpieces.net See specifically such in medical usage. Yes, in the pure metal form Titanium machining would be extremely difficult with the common machine metal tooling, abeit some state of the art innovative CNC guided laser technology is making inroads in this. The OPs concern was Nickel ... there is NO Nickel in Titanium Nitride, as may be present in some alloys and compounds ... this I believe the respondent was giving misleading data. Sorry, but my BSEd with Major in Earth Science prevailed ( I originally wanted to be Mining and Petroleum Engineer and have many credits in same, that contributed to said Major ).