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.

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 :-)

Here's my oven, more or less finished.

Nah, £3-4 I think.

Die you Pay like 10£ each? If so, they could be carbide.

I'm confused now as to what they are. I asked the guy I know in my local specialist tool shop for the best drills to cut titanium but it was a year or so ago. However, whatever they are they worked.

Where did you get small carbide drills? Those are quite expensive. Maybe try cobalt ones next time, they are not as brittle as carbide ones.

For colbalt read carbide. Well, they start with the same letter :-)

And you should use uncoatet drills, as the usual coating contains titan, wich causes problems working with titan.

Titan is quite a nasty stuff. You need to drill with mid-low rpm, with coolant, low pressure and take back every few seconds. For bigger diameters drilling out with a carbide drill works best.