View Full Version : Machining Titanium
10-05-2004, 07:07 PM
I need some help. A friend of mine gave me a couple small pieces of titanium. The largest piece is a 2" diameter rod about 3" in length. My friend is not a machinist so could not tell me anything about working this metal. I'd like to make a gearshift knob for my son's car and would need to tap metric threads in the interior as well as give it an exterior shape of some sort (I was thinking of kind of an oval shape). My equipment is a Myford 7B lathe. Can I use regular HSS tool bits or will I need to buy some carbide for this? Cutting lube? Any guidance would be appreciated.
10-05-2004, 08:21 PM
Titanium isn't too bad. It's tough but HSS (preferably with cobalt) will cut it. You'll need to run it like it's 304 stainless or a bit slower. When you drill it, don't let the drill dwell or you'll get work hardening which will wreck the tip of your drill. Use plenty of oil.....Threading it isn't bad. Make sure your tools are good and sharp.
I've cut titanium on my 10" Clausing with no trouble.
10-06-2004, 12:07 AM
I don't have enough experience machining titanium to be giving how-to lessons, but I will give you a few words of warning:
Titanium will burn, much as magnesium burns.
If titanium does catch fire, it's hard to extinguish. A Class D fire extinguisher or a granulated fire-smothering material (in a home shop environment, sand might have to do) is necessary.
The best ways to avoid a problem are to not allow chips to pile up, keep your cutting tools sharp, don't allow the tools to rub on the workpiece, and try to keep the chips you do make on the large side . . . don't make "titanium wool" or dust if you can avoid it.
10-06-2004, 06:12 AM
Thankee Andy, John. I didn't know that titanium would burn and I appreciate the warning. I keep a Class D powder type extinguisher attached on the left side of my lathe stand. I'm happy to hear that HSS will cut titanium and I already have some with cobalt which are ground and ready to work. Thanks again for the help.
10-06-2004, 07:34 AM
Do you have a Machinery's Handbook? The newer ones will have more info on speeds and feeds for you. The 18th edition that's at work has next to nothing in it, but my 21st edition that's at home has quite a bit of info. If you don't have one, I can get you the info.
Yes, it will burn. I've had grinding dust on a belt sander ignite and burn like smoldering paper across the table. Be careful. Make nice curls when you are turning it and you should be fine.
Grade 2 titanium is the easiest grade to work with. 6-4AL tougher but workable. Keep your tools sharp.
You're welcome, by the way. Yell if you have any other questions.
10-06-2004, 08:08 AM
I don't have the Machinery's Handbook. I do have K. H. Moltrecht's Machine Shop Practice Vol. 1 but unfortunately he doesn't put forth much info on cutting titanium. All I have been able to find is one reference to "Commercially Pure Titanium" and the recommended cutting speeds using HSS or Carbide. The fellow who gave me the two pieces told me that they were the "softest" of the three types of titanium. At this point I'm looking at a cutting speed of about 110 sfm using HSS. I'll glop Mobilmet S-122 cutting fluid on with an acid brush and see how it goes. Thankee again for your help.
Cutting titanium generates an astounding amount of heat, so some kind of coolant is a good idea. Wicked sharp HSS tools work fine.
just posted about my experiences with Ti on a jewellery thread....found it turns quite nicely actually with carbide or HSS tooling. Couldn't find a good way to drill the damn stuff...tried different lip angles/speeds/feeds/lubes....it was just a pain...slow going. Tapping as well was a real s.o.b....go real slow and back out frequently, in fact i broke a tap in one hole...maybe go a thou over or so on your drill size first and if there's any slack use a little loctite or something...just a thought. I would.. Good luck & take care,
10-06-2004, 06:37 PM
I appreciate the advice from all. I am fortunate in that I have an ample supply of drills - triple sets of almost all sizes I inherited from my father and a retired machinist. I'll take the drilling slow.
10-08-2004, 12:40 PM
I acquired a piece about 6" in diameter, two inches thick of grade two. Got it my head that I wanted to build a .410 revolver. A couple of guys I know were building them, and I thought it would be neat to have one just a little different. I got to hearing some of the horror stories of machining Ti, breaking drills, etc that I figured I better hold off till I learned a little more. That six inch piece makes a nice coffee cup stand on the hump in my pickup...been sitting there for about 12 years.
The guy with the plans passed away, and nobody knows what he did with them.
He did make some interesting firearms.
David from jax
Have gun, will travel.
10-08-2004, 09:49 PM
Drilling titanium can be relatively easy. Run slow, take your time, but push the drill a slight bit, careful not to dwell. 15 degree tip angle works best, as well as a thinned web. Spray on coolant. The chisel point will generate heat and create issues.
I have the class "D" fire extinguisher, but sand also works in a pinch.
Yes, I had a titan. fire once, chips from face milling. Put the fire out with kitty litter (speedy dry). Probably not the best effect and method, but worked.
10-08-2004, 11:13 PM
Be sure to employ unused kitty litter for this application.
10-09-2004, 07:32 PM
I machine titanium all the time, The burning issue is a bit overblown but be safe
none the less. I use carbide with plenty of coolant and obtain a beautiful finish.
If you are drilling or boring use quality
bits and drill the holes in steps, you can't just hog into this stuff.
Also, titanium will chew up a tap very quickly, again use quality taps and lubrication.