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Machining titanium on a lathe

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  • Machining titanium on a lathe

    I'm new to this group, and it looks great!

    I have a couple of questions for the (very) knowledgable machinists on this forum...

    I have acquired a 1" rod of aircraft titanium (from Boeing Surplus?), and I would like to know of any hints for cutting it on the lathe. I thought I'd just make a plain ring (finger ring) for starters to feel out how it cuts and finishes. I've read that it is as difficult to machine as 316 stainless...which doesn't like to be machined at all! I have a South Bend 10-Heavy lathe.

    So,

    1. Any pointers on lathe cutting techniques for titanium?

    2. Any pointers on getting a bright finish? Titanium finishes I've seen all seem to be dull...or brilliantly colored...

    Thanks!

    ------------------
    Pat Mullarky
    NW Computer Engineering
    Pat Mullarky
    NW Computer Engineering

  • #2
    Pat
    Titainium is naturally a dark grey material. Bright finishes are from PVD coatings or plating. How well it can be plated - I do not know.

    You need to use T-15 HSS bits or Inserts to machine it best. It does machine similar to 316 as far as SFPM goes, maybe a touch slower. If you have trouble machining 316 I do not think you are going to be able to do Titanium very well either. Some of the alloys are a bitch to machine - do you have an alloy number for it? It should be marked on the side of the bar.

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    • #3
      Based on my limited experience with titanium, it turns pretty well. At least the alloy I had did (no idea what it was). Wicked sharp tool, not too fast. Cutting it generates a LOT of heat, and titanium is a poor heat conductor, so things get hot fast. You'll probably want to use coolant of some kind.

      ----------
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      • #4
        You will definately want to use coolant when cutting titanium, it will ignite and burn if temps are high enough, these temps are not difficult to reach when turning. without the proper chemical you will not be able to extinguish the fire. DO NOT USE WATER AS A STEAM EXPLOSION WILL RESULT, IT WILL HAVE NO EFFECT ON THE FIRE.

        I use titanium quite often and by keeping it cool there is no danger. And it can be polished to a bright finish.

        ------------------
        Paul G.
        Paul G.

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        • #5
          Many thanks for the input!

          In the past I have successfully machined a few good 3/8" bolts from 316 stainless, but in my first efforts it felt like I was machining rubber stock with rubber bits! I soon learned that razor sharp carbide bits and slow speeds worked fine as long as I didn't hurry. But that was a long time ago...

          The temperature thing worries me. I didn't know titanium would burn in air at fairly low temps! I know magnesium can be very dangerous to machine in the home shop...the chips are extremely flammable even at room temperature. I've stayed away from any machining of magnesium for that reason.

          Any tips on a coolant? I usually machine just brass and aluminum...quite small parts (for optics)...and I've only dry-machined for a long time now. In fact, the only fluid I ever use these days is for tapping...using an ancient can of TapMagic.

          Pat Mullarky
          NW Computer Engineering

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          • #6
            One of the attributes of titanium is its temperature resistance, 2000*F, I don't think flammability is problem as it is with magnesium.
            For a small HSM lathe (Atlas, Southbend bench lathes, etc.) HSS is best to use. They cannot handle forces needed for carbide. A good sharp cutter, low speeds and coolant will work wonders.
            A good water soluble coolant, or sulfur cutting oil will be as good as anything. TapMagic is good for tapping, but pricey for lathework. Get a general purpose water soluble coolant, and apply with a pump spray bottle. A gallon will last for years. For aluminum, I still think WD 40 is best.
            Jim H.

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            • #7
              Fire is definately a hazard. Tried to set the lathe on fire turning the stuff, saw this glow under they ways grabbed the chip rake and dumped the glowing stuff on the concrete floor and covered with sand. Other than that it cuts well.

              ------------------
              Neil Peters
              Neil Peters

              When on the hunt, a broken part is better than no part at all.

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              • #8
                Although I have not tried it, I have heard that you can put it in dry ice before machining it to improve machinability.

                Greg
                "The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is." Winston Churchill

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                • #9
                  Some grades of Titanium cut like butter--PROVIDED YOU KEEP THE RPM DOWN. I frequently make custom rings for jeweller friend. Beautiful formed finishes are easy.

                  Reactive Metals Studio, Inc. ([email protected]) sells a 1"dia. X 12" long billet of jewelry grade titanium. Approximately $40.00.

                  Look up titanium rings on internet.
                  O

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                  • #10
                    crypto:

                    That must be just commercially pure Ti - no alloy. Cheaper than the rings I have seen!

                    Dave

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                    • #11
                      Dave,

                      Correct. Catalog describes it as Commercially
                      Pure Grade #1 Titanium.

                      Ring mfgs on internet offer their rings in two grades. One is harder and more wear resistant, an alloy of 6% Aluminum,4% Vanadium, 90% Titanium.

                      I have only cut the No. 1 grade. I make my tools out of 3/8" X 1/4" guage stock and harden and draw them with a torch. I use endmills to form the needed radius form using steep cutting angles (just angle the piece in the vise as you are cutting the radius) and I keep them razor sharp. If slow rpms are maintained the titanium seems to cause minimal wear. Makes the prettiest chips I have ever seen.
                      Oscar

                      O

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                      • #12
                        Pat,

                        If you are serious about making rings then you should purchase Gesswein's Platinum Buffing Compound Sample Set. www.gesswein.com
                        Also will need 4-4"dia. muslim buffs and a Satin Finish Buff.

                        Better yet make friends with a jeweller. All jewellers need a machinist friend.
                        O

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                        • #13
                          Do you recommend Shiite or Sunni buffs?

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                          • #14
                            Unc Dunc,

                            Oops! musliN not musliM. Had me guessing for while Unc. Now you've got me laughing. Must have been that SECOND glass of Merlot.
                            O

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                            • #15
                              If you want to put nice colors on the titanium ring? Put it on a wire loop and hold it over burning gasoline. If you do too much, buff it out and start again. Don't tell any one, I gave out that trick-SSSHHHH!

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