Hi Robin, I use a low speed in the bandsaw for cutting G5 Ti, I use around 40ft/min to saw off. I don't use an older blade that has dulled. Use a new or new or new blade. You want low chlorine water and coolant. It only catches fire if it gets really hot and often there will be sparks or something like that. Never seen it catch fire with plenty of water based soluble oil coolants. I use the concentration of 8% to 12%. Where possible I use deionised distilled water for mixing my soluble coolants in a bottle. I drill with new centre point style drills. An 8mm drill I use 300 rpm or so. I use as a drilling speed of 8m/min surface speed and just use the squirt bottle for the coolant. Ti will work harden if you take too fine a drill feedrate, and if the drill dulls. I use about 1.5mm to 2mm pecks. For outer turning I use the coated CCGT inserts , with a coating for Ti,/ Nickel/ tough to turn materials. Ti like cutting with the positive very sharp inserts. I use R0.4 for roughing, and the R0.2 for finishing. As for turning speed I use 15 to 16 m/min surface speed or no faster than 720 rpm that my lathe is speed limited to. So for the 20mm bar , can take 0.5mm cuts/ 1mm diameter at 19mm I would run around 250 rpm, and feed at around 0.2mm / rev or so if you have the power and coolant from the squirt bottle or from the coolant tap.

Neil

HSS turning tools and drills can do Ti but must be sharp, use a brand new drill if you can and keep the suds on it , if it loses it's edge up the hole it will melt the end if the drill , for turning i use brazed carbide tools for touching and HSS for finishing, tapping is difficult , it's not the material the taps are made of but the angles need to be right or it takes ages, when you know the ins and outs it's actually pretty good stuff to machine, ive made tons of components at work and in my workshop shame ive used all my stock up as its expensive to buy.

Interesting stuff Titanium, no experience myself but this web page gives a good summary of what makes Titanium awkward and what to do about it, see answers above!

Briefly, Titanium has low heat conductivity and elasticity, high reactivity and it work hardens in a blink. The answer is low rpm and high feed-rate, sharp tools, plenty of coolant at the cutting edge, never stop with the cutter in contact, maximised tool, machine and work rigidity and replace tools as soon as they wear.

The need to replace cutters quickly jumps out at me relative to Robin's question: 'Can I get away with HSS drills?' The answer is yes, but start with sharp ones and expect to consume several. Unlikely to 'get away' with blunt drills.

My casual approach to drilling mild-steel would certainly cause trouble if applied to Titanium. Mild-steel tolerates blunt drills and wobbly set-ups, cuts over a wide range of speeds and feeds, and isn't fussy about coolant. Titanium reminds me of Stainless, another special needs metal: I'm much more careful machining it, and avoid the rapid work hardening alloys if at all possible. Nonetheless stainless can be machined – it just has to be cut appropriately.

Titanium fire hazards should be low in a small workshop: the real danger is when a large pile of swarf catches fire and pouring water on it converts an exceptionally hot local fire into an explosion scattering flaming metal over a large area. A ton of burning Titanium is a big problem! I suppose Titanium could catch fire in a home workshop if the operator did absolutely everything wrong: made a big pile of dry swarf under the job, allowed the cut to work-harden, and then insisted on forcing a blunt drill into the job whilst ignoring all the danger signs! Most fire extinguishers are unsuitable for reactive metal fires, so don't use them on burning Titanium or Magnesium without reading the small print first. Doesn't seem likely Titanium soaked in water coolant would catch fire, but a bucket of sand in the workshop would be sensible, just in case.

What fun. Please report what happens Robin. Although my money is on success, failures are educational too!

Dave

A Class D extinguisher is what you need. Types that are water based just make things worse.

Andrew

I've managed to machine – usually small items – out of titanium using sharp HSS tools.

I think the issue with low thermal conductance is compounded by its mechanical toughness – the chip is difficult to separate from the parent material and doing so requires energy expenditure, manifesting itself as heat generated in both.

Drilling, IME especially with small diameters, can quickly produce temperatures high enough to let down the drill and, if the swarf jams in the 'ole, twist off the end of the drill bit. If that happens it can obviously present a difficult problem in saving the workpiece unless you're very comprehensively equipped. I once did that when trying (foolishly) to drill 1,8mm through a 50 mm long workpiece, and could only save it by finding a way to substitute a M3 x 10 dp tapped hole. Carbide drills might be an answer if you're prepared to splash the cash.

Titanium is a very poor conductor of heat. Which is why it will work harden very quickly. Some say treat it like stainless steel, and to a point that is true. Sharp tools with relatively high feed rates. But you have to keep the cutting edge tool. So they use through coolant drills etc. The only way to keep the heat low Ti is sharp tools and going slow rpm. The carbide tools as long as they are sharp will last about 5 times that of a hss drill before it needs resharpening. Some coated drills like the gold coated , can pick up with the Ti. There is a coating for Ti and it is a browny black colour. The other coating is a silvery colour as it is a diamond like coating. Uncoated carbide works well too , if it is the shiny one for Al. As you drill it, it will feel a little tough but easy if that can make sence. Then when it starts to work hardend, it will feel hard to push the drill, and it will squeel a little too. That means that the drill is dulling off or the speed is too high or not enough coolant or feeding too slow. With a 5mm drill you want to feed from 2 thou per rev to 4 tho per rev. On at 400 rpm you will be drilling at a feedrate of 1-1-/2 inches per min (40mm per min) to 3/4 inches per min(20mm per min) So your 8mm hole will be drilled in 12 seconds to 24 seconds as a guide example.

Neil