Machining Titanium? Gr2 or CP to be specific.

LCKT707

LCKT707

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Feb 26, 2015
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Started a side project recently that involves medical grade Titanium; or Grade 2 to be specific (99.97%) and after eating through tons of equipment machining it like steel (durr) I decided to do some good ol' brain learnin'. Read up a lot on it and got loads of great information that answered a lot of my questions except for one... how do you do it?

I'm limited to my 2x72, Dewalt Angle Grinder, Dremel, and hand tools. I read that it work hardens, so to cut aggressively. Then read contradicting things other places. I've tried nonferrous cutoff wheels, ferrous metal cutoff wheels, aluminum cutoff wheels... this Ti machines so obnoxiously lol. Hard to cut like S90V but slags and clogs and eats wheels like aluminum... steel cutoff wheels seem to last the longest on it so far oddly enough. 100% ceramic abrasives seem to do no difference on grinding this stuff than AO.

So... what do? is this just what you deal with when working with this stuff? Do I need to pony up and get a bandsaw? Should I just send it to water cut?

Thanks in advance for any input.
 
To cut - a hacksaw or chop saw works great on bars and a metal cutting bandsaw on larger pieces. I like to to use bars and just hacksaw to length, it only takes a minute to cut a piece. I like to go to waterjet if I need to do a large group.

Grind slow and use ceramic belts... try not to let it spark so use minimal pressure, sharp belts and low speed. Most any ceramic belts are good but my favorite belt on Ti is the Yellow Cubitron 967 by 3M.

HSS or Cobalt bits are fine, with a rigid setup I like carbide. Use a low drilling speed and high feed pressure, keep everything cool.

I don't think Ti work hardens in a significant way (I'm talking 6al4v or CP/Grade 2) and I know a lot of people will disagree with that statement... just cool it and use sharp bits if it is getting tough to drill.

Ti can be tricky to work with but isn't really too bad once you get used to the nuances. I'm working with a lot of Copper at the moment and it seems to be the same way.
 
It will build up alpha case, which is what rapes tooling, especially when you're using something that's taking small amounts of material off and generating lots of heat in the presence of oxygen.


You'll probably hear some recommendations on friction cutting, which I've never tried, but precludes you having a fast saw, and I can only imagine how much that promotes alpha case formation.



Personally I've never had a hard time cutting it with a bandsaw on low speed with high feed rates. I also do the same when grinding. I ground 30 chisel ground Ti blades that were carbidized with one 3m 984F Cubitron II 80 grit belt, and it was still cutting fine. Half the FPM of steel (VFD set to 40% or so with the 2x jumper set and a 5" drive wheel) and pretty heavy steady feed, but cooling regularly.


A hacksaw is probably your best bet, just remember when you're cutting thin stock to pick the appropriate tpi, and don't peck at it. For instance when cutting 0.045-0.070 stuff for liners etc, I use a 24 tpi good quality bi-metal blade, and I feed hard.
 
Daniel and javand thank you both very much all of that information is exactly what I needed to know. I did try a hacksaw and noticed it cut relatively quicky but stopped because "powaaaaaah" lol. All the information on machining Ti that I gathered all came from people who weren't doing it in the same context we all seem to be doing it. So this clears everything up I need to know thank you both, again.

12345678910 said:
Grade two is commercially pure


Try grade five, 6al4v
Click to expand...

I was under the impression it stood for chemically pure but then again i've always been terrible with acronyms ever since LOL's inception haha. This project like I said though requires Grade 2 as it is medical grade.
 
LCKT707 said:
Daniel and javand thank you both very much all of that information is exactly what I needed to know. I did try a hacksaw and noticed it cut relatively quicky but stopped because "powaaaaaah" lol. All the information on machining Ti that I gathered all came from people who weren't doing it in the same context we all seem to be doing it. So this clears everything up I need to know thank you both, again.



I was under the impression it stood for chemically pure

This project like I said though requires Grade 2 as it is medical grade.
Click to expand...

Is it some sort of jewellery ?


Try some 6al4v

http://www.supraalloys.com/medical-titanium.php

Medical Grade Titanium

Titanium 6AL4V and 6AL4V ELI, alloys made of 6% Aluminum and 4% Vanadium, are the most common types of titanium used in medicine





CP commercially pure is the least pure of the grades.
 
Grade 2 is really good for domed or spun pins, and situations where you want formability over springiness and scratch resistance. Although any Ti I've ever used scratches just by looking at it sideways. Most other purposes grade 5 is what you want.
 
CP titanium is way softer than 6AL4V. Almost a different animal in some ways. Same flexibility (low modulus of elasticity) and low heat conductivity though...

6AL4V doesn't work harden much. CP probably does, though I haven't noticed it much. I don't think heat has much to do with it. I think that misconception comes from people noticing work hardening when the work gets hot, rather than recognizing the rubbing and subsequent smearing that actually caused the work hardening.

Titanium is strong and flexible, so it moves easy but doesn't want to cut, so you need a rigid setup, low depth of cut and large chip load (high feed rate). This keeps it cutting. The low thermal conductivity means heat builds up in the cut very quickly. For most folks, this means you're going to need low SFM (RPM) and coolant to keep heat in the cut manageable.

I know this doesn't really relate well to the OP, but for those machining it, this is a good approach.
 
There are many interesting alloys that we usually don't hear about . There are Ti -Nb and Ti -Nb-Zr alloys that are very suitable for medical use .[Don't ask a med tech as they don't know metallurgy !! LOL] Some even have a martensitic transformation for strengthening .Ask Mecha our Ti sword man . British Blades has a good sticky about Ti you can check.
 
12345678910 said:
Is it some sort of jewellery ?


Try some 6al4v

http://www.supraalloys.com/medical-titanium.php

Medical Grade Titanium

Titanium 6AL4V and 6AL4V ELI, alloys made of 6% Aluminum and 4% Vanadium, are the most common types of titanium used in medicine





CP commercially pure is the least pure of the grades.
Click to expand...

CP Grade 2 is what the project and market calls for. It will be radically changing temperatures from red hot to room temp in end use, this apparently is the best type for that.

Nathan the Machinist said:
CP titanium is way softer than 6AL4V. Almost a different animal in some ways. Same flexibility (low modulus of elasticity) and low heat conductivity though...

6AL4V doesn't work harden much. CP probably does, though I haven't noticed it much. I don't think heat has much to do with it. I think that misconception comes from people noticing work hardening when the work gets hot, rather than recognizing the rubbing and subsequent smearing that actually caused the work hardening.

Titanium is strong and flexible, so it moves easy but doesn't want to cut, so you need a rigid setup, low depth of cut and large chip load (high feed rate). This keeps it cutting. The low thermal conductivity means heat builds up in the cut very quickly. For most folks, this means you're going to need low SFM (RPM) and coolant to keep heat in the cut manageable.

I know this doesn't really relate well to the OP, but for those machining it, this is a good approach.
Click to expand...

It related perfectly as I plan on machining it in the future as well, and I always love to learn more information. Thank you for the response! Can't wait for your next 3V batch. Take care.
 
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