4 ms·

It seems that feeding and cuting speeds are quite different from aluminium or steel. Also if it overheats it's like if you heat treat it, it becomes almost impo

by omegant 13y ago

It seems that feeding and cuting speeds are quite different from aluminium or steel. Also if it overheats it's like if you heat treat it, it becomes almost impossible to cut. That's why you must use coolant if you want to have some good results.

varjag 13y ago
It depends on alloy. Commercial grade pure titanium and grade 5 alloy (probably 90% of Ti stock out there) are easy to machine. Harder than aluminium, sure, but not anywhere close to hardened steel. Titanium can be heat treated to an extent it doesn't gain that much. Also you really need a furnace for that kind of temperatures. You need coolant if you use high cutting speeds, it also helps to remove swarf. It's still possible to machine titanium dry with appropriately formed cutter and get a fine surface. (Source: I also turned two titanium rings)
- KMag 13y ago
  Yes, the grandparent is probably misattributing annealing of the cutting tool to hardening of the Titanium. Titanium has a very high melting point and very low heat conductivity (for a metal). Using a hardened steel tool to cut Titanium too fast without sufficient cooling will heat up the tool hot enough to anneal the tool. It appears the Titanium has become harder, but in fact the steel tool has become less hard. Note, I'm talking about cutting rates that you'll achieve by hand or by conventional CNC machine tools. At very high cutting rates, the chip (discarded metal) carries away significant amounts of heat, and in some cases increasing cutting rate actually reduces tool temperature and prolongs tool life. This was an active area of research in the late 1990s.
  - varjag 13y ago
    Yes annealing at the edge indeed can happen with HSS bits when ran dry. The point about heavy cuts is interesting, although I'd be very uncomfortable without coolant - thin titanium swarf readily ignites in the air.

by omegant 13y ago

varjag 13y ago

It depends on alloy. Commercial grade pure titanium and grade 5 alloy (probably 90% of Ti stock out there) are easy to machine. Harder than aluminium, sure, but not anywhere close to hardened steel. Titanium can be heat treated to an extent it doesn't gain that much. Also you really need a furnace for that kind of temperatures. You need coolant if you use high cutting speeds, it also helps to remove swarf. It's still possible to machine titanium dry with appropriately formed cutter and get a fine surface. (Source: I also turned two titanium rings)

KMag 13y ago
Yes, the grandparent is probably misattributing annealing of the cutting tool to hardening of the Titanium. Titanium has a very high melting point and very low heat conductivity (for a metal). Using a hardened steel tool to cut Titanium too fast without sufficient cooling will heat up the tool hot enough to anneal the tool. It appears the Titanium has become harder, but in fact the steel tool has become less hard. Note, I'm talking about cutting rates that you'll achieve by hand or by conventional CNC machine tools. At very high cutting rates, the chip (discarded metal) carries away significant amounts of heat, and in some cases increasing cutting rate actually reduces tool temperature and prolongs tool life. This was an active area of research in the late 1990s.
- varjag 13y ago
  Yes annealing at the edge indeed can happen with HSS bits when ran dry. The point about heavy cuts is interesting, although I'd be very uncomfortable without coolant - thin titanium swarf readily ignites in the air.