Mr. Goob,
What is it that requires you to machine Ti verses Fe and Al? My experience is limited to making three pullys out of Al on a lathe 20 years ago (I found out the cutting utensil was upsidedown which explained the groans I got from the head machinist–sometimes it helps to ask questions first). And how expensive is it to tool up for a hobby machine shop?
user_hostile Steel is a benchmark. It machines nice, good solid chips coming off, nice finish, reliable measurements after cutting. Aluminium is much gummier. It bugs onto the tools when you are cutting. Hard to describe. Just needs a different speed and feed and depth of cut. (Speed= rpm tool or piece is spinning. Feed= how fast the tool moves across the work. Depth of cut= How deep you are digging the tool into the workpiece.)
OK think of cutting firewood. Steel is like a 2 year old aged hardwood like oak. Clean crisp, you know what to expect as the saw goes through it. Cutting Aluminium is like cutting into fresh pine. Softer but gummier you can cut faster but get a different finish on he cut.
Not the best analogy, but should get the idea across. Different tool types make a difference. Cutting wood do you use a fine tooth hacksaw or a large tooth backsaw. Same idea with milling cutters on metals.
Back to titanium. Not any harder or easier than steel or amuminium to machine, just different. When it’s cutting, it’s feels dense like lead. Spin the rpm’s way up and take shallower cuts is the start.
Now define “hobby machine shop” and I’ll work with you on tooling.
Considering titanium is the ninth most abundant element in the Earth’s crust (0.6% by mass), it can’t be too expensive. Any expense is probably more likely due to it being difficult to purify (like alumninum, when it was first discovered) or to work with.