Here's my oven, more or less finished.

I seem to keep hearing these stories of how hard Ti is to machine or cut -- Ti is NOT hard -- it is Though -- Highest obtainable hRc hardness in Ti Alloys is found with full Beta-Titanium (used by Mission Knives for their diving knives) and reaches about 46-48 Rc -- any really good carbon steel will reach 58 Rc as a routine.

Most Titanium bolts on the market are Grade 5 Ti -- They can be cut quite easily with normal HSS steel drills -- the Grade 5 bolts are not as hard as even an 8.8 Din Steel bolt, even though they have higher tensile strength and yield strength-. The only very important thing is to have SHARP drills (and god cutting coolant helps)
The HSS-Cobalt jobber drills do the job very nicely, since they stay sharp for longer. Carbide drills are a big no-no in Ti because Ti is very tough (high tensile combined with relatively low hardness)  Normal "TIN-coating" is a no-go, "TiALN" is the answer if using coated tools.

Just try cutting M18x1 internal threads in Grade 5 Ti using a tap -- The sound my Colchester Lathe makes even at lowest RPM tells a tale :-)


"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)

I never said titanium is hard. I said is hard (difficult) to work with. At least compared to regular steel or aluminium.
Hardness and tensile strength are all most proportional. Both characterise the resistance against (fatal) ductile deformation. Source: 3 semesters of material science at the university.
Grade 5 titanium has a tensile strength of about 900N/mm^2 and therefore is less tough (And hard) than an 10.9 steel screw (first number x100= Rm).
The problem however ist it's low thermal conductivity and a specialc chip shearing. Source: 1 semester of "chipping technology with geometrical defined edges".
This leads to thermal stress for your drill (carbide ones have a much higher heat tolerance, but are more vulnerable to thermal shock than hss ones) and a problem with the removal of the cut off material. This means you should drill only a short distance, then remove the chips out of the hole. For initial drilling, carbide drills are not recommended (but the hobbyist usually don't have any either), as they tend to break because of the stuck chips. But if you are planning in drilling much in ti, a secondary carbide drill to get to the final diameter could pay of.