Machining Titanium

[newdogs]

Hello,
I am new to this forum. I have some questions about machining titanium I'd like to put to the forum I have a current application for titanium and I have no experince machining it.

The application involves machining several plates from .063 plate stock that are assembled together using either rivets or or machine screws. The finished product is a whistle and each plate has a series of holes drilled into it, one hole has a .125" ball end mill counter sink, and two holes have counter sinks for either a rivet or flat head screw. The plate are milled from the sheet stock and are made of of a series of radius cuts. The finished whistle is about 1.6" wide by 1.4" in height deburred along the edges and then has to be polished & engraved.

I have made several thousand of these out of brass, steel, & alumium but this would be the first for titanium. I already have drawing made up but have not programed for the parts since I really have no idea of speeds & feed rates or what kind of end mills to use. I do know it's important to take big chips and to try to keep the part cool to prevent hardening but beyond that I don't know.

Any help or suggestions would be greatly appreciated,
Rob

[joecnc1234]

Titanium is not a magical material. Look in the machinist handbook for feeds and speeds I think it's somewhere aroung 150 sfpm for carbide. titanium is a great material to machine once you get the feeds and speeds worked out the tools last a decent amount of time.
Joe

[archimedes]

Greetings Newdogs,

Joe is spot on for the experience of machining titanium. It is beautiful
for its cleanliness and rich patina after a good machining. I liken it to
a 300 series Stainless steel for speeds and feeds. And go down from there.

Two things quickly come to mind -
1. your workholding methodology
2. your cutting coolant applicator

Whatever Ti alloy you have chosen, its machinability and success therein
will depend on how well you can hold it. From there the learning curve
begins to flatten out fairly quick.
Titanium is very springy. It will want to absorb, rather than resist and
then will come right back at you. Keep this in mind. Take time to examine
your workholding setup(s) for the other materials and then scrutinize its
effectiveness for a very different material.

I have machined 6al-4v in a 1980's 5c collet CNC lathe from roughing down
to finish to threading to drilling thru; using TrimSol cutting coolant standard
ratio mix.
I have also machined the same material in my Lagun manual knee mill with
a 2 flute HSS 1/2" EM. My cutting coolant was some Tapmatic Edge creme
mixed with Tapmatic TriCut. But I use to use good ol' pipe threading oil
and no problems. I applied both liberally with an acid brush swipe.

I like carbide inserts on the lathe, however I have found HSS to work
best when using the Lagun's more slower speeds and feeds (I have a
manual change belt head). On the Lagun I set the belt on pulleys to give
a 100 or 170 rpm and adjusted my X axis drive to a very slow feed.
I do remember trying a 3 flute 1/2" EM once, but I can't remember
if I found satisfactory results. I do remember a 2 flute HSS having
consistent results over quite a number of delicate cuts.
Of course all of this was much easier to attempt when I got the
workholding figured out! Bondo was the saving grace . . . .

Hummmmm, I am not sure if there is anything else --- workholding is
your key. Go slowly from there.
I am sure many top notch aerospace and medical guys here can offer
better insight and I would like to read their replies as well for my own
improvement. I hope my slight knowledge might offer a comfort zone
for your first attempt.

scott

[cdlenterprises]

I haven't machined too much titanium but there are two things that you have to know about it:

1) It doesn't conduct heat well. This means that most of the cutting heat will be "reflected" back towards the tool so good coolant flow is a must.
2) It has a low modulus of elasticity. This makes it very "springy" so it would rather deflect away from the tool rather than be cut.

For those two reasons it is very important to keep your tools in good condition(i.e.: sharp and cool) It also has a tendency to gall so tooling condition becomes more critical.

Other than that, it's not unlike any other alloy. There is a certain "window" that you have to be in for speeds and feeds. Stay in that window and it cuts relatively nice. Go outside of it though, and you'll run into problems.

This link contains some good info about titanium. Check it out...

http://www.supraalloys.com/Machining_titanium.htm

Good luck!