Cutting titanium with HSS?

[WarrenP]

Hey Everyone, I was wondering is it possible to cut titanium with hss tool bits? I didn't really want to buy carbide right now so I am wondering.... But, If I do need carbide is there any suggestions as to which type I would need. Thanks in advance for you time. Warren

 

[Bob Korves]

The first question perhaps should be "Does the part need to be made from titanium?" I must admit that I do not remember ever having titanium in my hands, and have got along pretty well without it. It is light and strong and resists corrosion. Does what you are making need all three of those properties? Titanium is also expensive and not easy to cut well.

 

[mikey]

I haven't turned titanium, either. I know just enough about it to get in trouble. Titanium is similar to stainless in that it doesn't dissipate heat well. Most of the heat is concentrated at the point of cut so work hardening is a real thing. Consequently, I would opt for carbide instead of HSS.

Because of it's similarity to SS, I would go for a positive rake insert with a coating recommended for Titanium - PVD maybe? I would machine it like SS, meaning a continuous cut without dwelling, a deep enough cut to minimize deflection and coolant to reduce temps at the point of cut. If it was me I think I would try a CCMT insert.

 

[e189552]

I have turned a bit of TI in my time. As with most anti-corrosive metals, you get a built-up edge deposit on the cutting tool. When this breaks off it takes a portion of your cutting tool edge with it. Carbide is especially susceptible to such edge wear. I would suggest using M42 or M47 cobalt with a positive rake and medium nose radius. As some of the other posts have noted never let the tool dwell on the workpiece, TI will work harden in a heartbeat. Always found slow SFM, heavy feed & deep cuts worked best.

 

[SamI]

I do a reasonable amount of titanium turning. It’s pretty easy going IMO but as others have said it heats up real quick which is a big problem with HSS, especially drilling where the heat build up at the cutting edge has nowhere to go. I’ve melted The ends off of more than one drill bit!

That being said, a cobalt drill bit with a sharp edge cuts through the stuff with no bother at all. I’m pretty sure that as long as you can keep the heat under control and have a sharp cutting tool you’ll manage with little problems. If you’re not using coolant keep the speed down and if the workpiece gets too hot to touch then leave it to cool off for a bit or blast it with some air.

Be wary of the chips and clear them regularly. They are a fire hazard. It’s not uncommon for chips to spontaneously ignite when cutting without coolant and if you’ve got a big pile of them in your chip tray these could easily ignite. It looks pretty when it burns but don’t look at the flame! It’s like looking into the sun - it actually hurts your eyes!

The only time I’ve found work hardening to be an issue is with blunt cutting tools. Keep them fresh and you’ll have no problems.

 

[wrmiller]

I occasionally made compensators out of titanium. Mills OK, turns OK, but like Saml mentioned above, I've melted a few HSS drill bits in this stuff. Tough, and work hardens if you stare at it too long.

 

[WarrenP]

Sounds like I need to get some carbide tools. I was just planning on making a ring out of titanium, would think not much facing to bring it down from 1.5 to about 1 inch, but need to drill out the hole in the middle which sounds like it will generate alot of heat just in that part itself. Probably should do the facing first then drill the hole in case it gets hot and hardens.

 

[SamI]

You’ll be alright drilling first then facing. How deep are you drilling, my guess would not be very far. I’ve only had problems drilling titanium when the hole gets to 2 or 3 times the diameter of the drill bit. If it were me I’d drill to depth then face, turn the OD then bore the ID if required. As long as your tool bits are sharp work gardening won’t be a big problem. Personally I find it easier to turn than stainless and it threads quite nicely (as I found out when picking up a bar of Ti by accident instead of 303!).

I think where I went wrong in the early days was cutting at too high a speed. When I first started cutting it was surprisingly easy so I upped the speed and that’s when the heat becomes a problem. Keep it fairly slow (probably about 3-400 rpm for an inch diameter) and have at it.

 

[P. Waller]

My experience with Ti. Having only worked on alloys that have been post processed such as 6al4v.
External work is straightforward such as turning and milling, internal work can prove difficult such as drilling and tapping.

This is always dependent in the alloying elements and any post process treatments that the material goes through before you receive it, there are several "grades" that are commonly available, some machine easily and others do not. Use the material that fits the application you require.

If you are using it because you simply want to include the word Titanium in the products description and there are no other factors that make it a good choice then this is the one as it is the most commonly produced alloy. In recent years there may well have been more easily machined grades developed for the jewelry industry, this I do not know.

 

[WarrenP]

Thanks for the responses. Since it is only a ring , not very big, I thought I would give hss a try and if any problems get a carbide tool unless someone feels that would be useless to try. Thanks again.