# Machining titanium 6Al-4V



## precisionworks (Feb 22, 2012)

This a topic that rarely comes up here & that seems odd. Most every high end light uses Ti-6-4 & titanium is the metal of choice among custom builders. Just a few of my thoughts to get started & please post with your own experiences.

Lots of machinists (self included) compare this metal to 316SS. Personally I'd rather machine 6-4 than 316 as 6-4 gives such a beautiful finish right off the tool, as shown in these photos:

















Coated carbide is the tooling of choice for 6-4. Heat at the cutting tip can reach as high as 2,000°F and the correct coating & coolant help moderate the heat & extend tool life. 

Machining speeds are slow. Drilling is often at 20-30 sfpm but sometimes as high as 50 sfpm. Turning speeds of 100-150 sfpm are common. Feed should be as much as the tool can stand to ensure that the tool is cutting & not rubbing - which leads to work hardening. Sharp tools & a stiff setup are essential with this springy material. Coolant is good & more coolant is better 

Good info here to get things started.


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## badtziscool (Feb 22, 2012)

I like the flutes added on the SWM. :thumbsup:

It's funny that you posted that link. Literally just yesterday, I was searching on how to clean and restore that machined titanium finish and I came across that exact same article. Pretty interesting read. I'm a computer scientist and IT professional by day, but if I were to have a career change, it would have to be a machinest. I think it's just awesome to physically produce things that are functional but also works of art out of exotic materials.


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## 340wedge (Feb 22, 2012)

Looks good prescion. I plan to get into machining some titanium myself and just ordering the last of the tools before the cnc lathe gets here. I have way too many ideas to let myself slide and not go for it. 

Any bets on how many times ill crash it before getting a handle on g coding?

Also debating between a mist, full flood coolant or just some thick high sulfur to help make the tools last longer. Any suggestions?


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## precisionworks (Feb 22, 2012)

> debating between a mist, full flood coolant or just some thick high sulfur to help make the tools last longer. Any suggestions?



I'm not a fan of mist, no matter how it's done. MQL is so much cleaner, more effective, doesn't smell up the shop,etc. I milled ten titanium slots today and turned the groves on a V10R Ti, both with AccuLube 2000. Maybe four hours total run time on both machines. Used about two or three tablespoons of lube.

MQL (and mist) are both effective when the tool point is visible - OD turning & facing, slotting, face milling, end milling, etc. Flood is the clear winner in deep holes, anything three diameters or greater, including both drilling & boring. Sulfur based lube is the best of the best for tapping.

Some of the newer CNC machining centers can be setup for through the tool MQL or through the tool flood. Many drills are available already bored for coolant, as are reamers, larger taps, turning & boring tools, etc. 

You cannot appreciate hot titanium boring chips are. They cause immediate smoking with many lubricants, even running at a gentle speed and DOC.


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## Th232 (Feb 22, 2012)

precisionworks said:


> You cannot appreciate hot titanium boring chips are. They cause immediate smoking with many lubricants, even running at a gentle speed and DOC.



Having machined Ti for the first time recently, I can attest to this.

In my (very) limited experience, a couple of additional tips are:
* If you have to use a large dia drill bit, make sure it's not plain HSS or that you have flood cooling (I don't...). They burn out really quickly. Actually, I've now made it a general rule to not use HSS for any Ti machining, except maybe small diameter drill bits.
* There's carbide, and then there's carbide. This is true for all tooling in all materials, but none more so than Ti in my experience.


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## precisionworks (Feb 22, 2012)

> If you have to use a large dia drill bit, make sure it's not plain HSS or that you have flood cooling


Titanium can be drilled with HSS but the speed (or lack thereof) will put you to sleep. Figure a solid carbide or carbide tipped drill at 50 sfpm, cobalt at 25 sfpm, HSS at 10 sfpm - with flood coolant on all three. Without coolant the speeds are reduced for all three materials. 

One problem with most HSS twist drill is the 118° included angle of the point. 118° is good for general purpose drilling in mild steel but 135-140° works better in harder materials like Ti. Regrinding to the larger angle can allow a HSS drill to make it through one or two holes before resharpening is needed. Cobalt drills have a thicker web & will withstand lots of thrust. Carbide drills work best but can be expensive. The carbide tipped drill is a good alternative & the cost is sometimes not much more than cobalt. Lots of info in the Rock River Tool catalog.


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## easilyled (Feb 23, 2012)

Is the Ti used for the Sunwayman V10R definitely 6Al-4V grade then?
Given its price-point, I would have thought that it was more likely to have been made from CP Ti.


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## precisionworks (Feb 23, 2012)

easilyled said:


> Is the Ti used for the Sunwayman V10R definitely 6Al-4V grade then?
> Given its price-point, I would have thought that it was more likely to have been made from CP Ti.


Only SWM can give you that answer 

I mostly buy titanium from McMaster - their price is comparable to other USA suppliers. A 25mm rod 2m long in Grade 2 costs $488.33. That same 25mmx2m in Grade 5 is $496.18, only 1.5% higher in cost. Just about identical pricing from my source.

SWM certainly buys their stock for much less than I do. A 25mmx100mm rod would cost $25 from McMaster & there's no way that they have that much cost in raw material.


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## easilyled (Feb 23, 2012)

precisionworks said:


> Only SWM can give you that answer
> 
> I mostly buy titanium from McMaster - their price is comparable to other USA suppliers. A 25mm rod 2m long in Grade 2 costs $488.33. That same 25mmx2m in Grade 5 is $496.18, only 1.5% higher in cost. Just about identical pricing from my source.
> 
> SWM certainly buys their stock for much less than I do. A 25mmx100mm rod would cost $25 from McMaster & there's no way that they have that much cost in raw material.



Thanks for the price insight and apologies if I diverted the topic of discussion. (I didn't realise that there was so little difference in the cost between the two grades of Ti available from the US.)


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## precisionworks (Feb 23, 2012)

> apologies if I diverted the topic


Not a problem for me. It seems like lots of MMM threads diverge but that keeps it interesting.

There may be a larger cost spread between Grade 2 & Grade 5 in Europe or in Asia. FWIW Ti-6Al-4V is consistently responsible for 45% of all industrial applications, year after year. Because it is so widely used the price is often low compared to other less used titanium grades.

Grade 2 does have one big advantage - it can be machined at twice the speed of Grade 5. Since machine cycle time accounts for a large percentage of total part cost this can be a deciding factor ... if the strength of Grade 5 is not needed.


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## PhotonFanatic (Feb 23, 2012)

Well, I just got in some ceramic inserts, mainly for machining some hardened steel. The first piece I tried it on didn't have any sparks and the material was cutting easily, so I presumed that it was less than 45C Rockwell hardness and decided to go back to my usual inserts.

But, before I put that ceramic insert away I thought I'd try it on some Ti. :devil:

Of course, my knowledge of machining with ceramic inserts is limited to an online article written years ago, but it seemed to still be relevant; plus, I watched a YouTube video. Almost as good as staying at a Holiday Inn Express, right? 

So what I had read said to run the piece at high SFPM since the insert performs best with high heat--well, Ti should do that! Plus it said no coolant--fine with me as any cutting fluid would be smoking in an instant. :shakehead

My piece was 27mm in diameter and I ran it at 800 rpm with a DOC of .25mm, or 1 thou, roughly. Was there heat? You bet--and some minor sparks at the tip of the cutting tool. The Ti was coming off with a bronze color, so it was warm.

The insert cut through that Ti at about 220-225 SPFM, which is pretty damn quick. Was nice to see that there is something that could be used for rapid removal of Ti while turning. The surface finish was pretty nice, too--not as nice as a large radius AlTiN coated carbide insert would provide, but acceptable for what it was doing.

Only drawback--the insert had fair bit of notch wear, probably because I was taking numerous cuts at the same DOC--something the article suggested should be avoided--they suggest varying that considerably. Live and learn--I'm glad I gave it a shot.


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## precisionworks (Mar 1, 2012)

Ceramics & especially cermets are a great choice for titanium. Ceratips from Kyocera are one of the most widely available inserts on eBay & some are not much over $1 USD. Their electronic catalog downloads quickly and has complete grade charts click here.


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## Anglepoise (Mar 3, 2012)

Fred.........Have you had a fire yet using the cermet and ceramic ??


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## mohanjude (Mar 3, 2012)

I am a novice but having drilled half a dozen fins and cutting the flutes into the Bezels of several V10R Ti I can only assume that the Sunwayman Titanium is soft. I am not using anything expensive to do this either - just straightforward HSS drill bits and occasionally cobalt on my desktop lathe. Not even using a fast flow of coolant either. I thought I was going to sweat drilling through those fins.. it was very straightforward. I wish I had done this a month ago instead of worrying about the properties of titanium and the technicalities. Everybody body I spoke to get advice including experts and many people who worked with aluminium had me scared thinking that I was going to be drilling into forged Vanadium steel with the V10R. I think there is a fundamental difference between the Alloys used in the aerospace industry and flashlights. The reality for me is that I can drill my Sunwayman V10R very easily and there is nothing tough about it. It will be interesting to see how the other Titanium flashlights compare. If they turn out to be as easy to drill and mill I will be suprised. I am not rushing to drill them simply because some them are hard to find and cost 5-6 times of the V10R

I have been drilling aluminium for a long time and I did not find working with the Sunwayman Ti any different in practice with what I had to do. I haven't had a go at Mac's or Mcgizmo lights yet but before I do that I am going to buy some barstock of the hardest titanium I can find locally and see how it compares.


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## precisionworks (Mar 3, 2012)

> before I do that I am going to buy some bar stock of the hardest titanium I can find locally and see how it compares


Ti-6-4 is the flavor to look for & it's also the most commonly used (and most widely distributed) alloy in the world today. I agree that Ti-6-4 isn't difficult to machine but it certainly is different.

First is the propensity to go through expensive tooling at an alarming rate. The bodies did drill more easily than I expected & tapping for 4-40 screws also went well ... but the solid carbide drill cost $80 & the powdered metal tap was another $40. It was a great relief to get those ten holes drilled, tapped & done. It won't bother me a bit if that drill & tap don't ever again see the milling machine  One reason that Ti is different is that whatever heat is generated at the tool point stays right there. Extreme heat causes even the best coated inserts to soften & become plastic, the edge is lost, the insert fails (often without warning) & the part is scrap. Scrapping a $500-$2000 light is guaranteed to ruin your day.

Another issue with Ti is that has stiffness comparable to overdone linguini. Not a problem when working on a short 25.4mm bar close to the chuck with tailstock support. A big deal when taking either roughing or finishing cuts on a thin walled tube as the tube is pushed away from the tool.

Work hardening is not exclusive to titanium - 316 stainless, 4140HT, AR400 & AR500, & many tool steels share this characteristic. Push a drill into Ti with too much feed & the drill snaps. Feed it too lightly & the bottom of the drilled hole becomes so hard that nothing will ever again go through. Scrap that part too 

There are lots of modders & builders on the forum who do not want to pay the tuition to learn titanium machining. It isn't cheap.


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## precisionworks (Mar 9, 2012)

Kyocera was mentioned in post #12 as an insert source. Not as huge as either Iscar or Sandvik but much more nimble. 

I requested a free sample insert by email. Since none of the samples were designed for titanium a short note was attached to my request. Less than one day later the regional rep phoned to ask specific questions about the insert shapes I wanted to use. We talked for 15 minutes or so & he said Kyocera can take any standard insert & apply a titanium-specific hardcoat - and I don't have to buy 1,000,000 inserts :nana: 

Insert life on the current DNMG-433 is endless but the pointed nose DCGT has a life measured in single minutes. That's the price of running an aluminum-specific shape in Ti-6-4. The rep is coating & sending out both shapes for testing in my shop. Don't have the DNMG or the DCGT special inserts yet but did get this in the mail:






If you want to try the CNMG-4xx insert fill out this sample request form.


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## PhotonFanatic (Mar 25, 2012)

Anglepoise said:


> Fred.........Have you had a fire yet using the cermet and ceramic ??



No fires, but plenty of sparkles. :devil:

I'm not using those inserts that much, nor will I try them at such high SFM rates in the future.


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## unterhausen (Mar 25, 2012)

I assume you are just turning? I am interested in milling, but I'm not sure the operations are much different when it comes right down to it.


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## precisionworks (Mar 28, 2012)

> not sure the operations are much different


The biggest diff is that lathe work is single-point where milling uses multiple cutting edges. If the same insert shape is used & (for example) the mill tool runs four inserts the chipload/tooth is either:

1/4 as much at the identical DOC, resulting in much faster feeding.

OR it's identical at 4X the DOC.

Those two examples are over simplified but illustrate the point. High flute counts are becoming more common for titanium milling tools. Look at this video showing a 20-flute tool in Ti-6-4 & you might think the material was aluminum 

Modern Machine Shop


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## Kestrel (Mar 28, 2012)

precisionworks said:


> Work hardening is not exclusive to titanium - 316 stainless, 4140HT, AR400 & AR500, & many tool steels share this characteristic. Push a drill into Ti with too much feed & the drill snaps. Feed it too lightly & the bottom of the drilled hole becomes so hard that nothing will ever again go through. Scrap that part too



That's very interesting, I didn't know it was that sensitive.


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## precisionworks (Mar 28, 2012)

Kestrel said:


> That's very interesting, I didn't know it was that sensitive.


As long as enoug pressure (feed) is applied to produce good chip flow the materials all work well. It's easy to get into trouble by running the tool too fast (which generates excess heat) and letting the tool dwell, even if just for a second. In all heat sensitive materials the rule is that the tool has to be moving forward or moving backwards (withdrawing from the work). 

316 stainless, 4140HT, AR400 & AR500,Ti-6-4, etc. are hardenable to around 50 Rockwell C (475 Brinell). That hardness can be drilled with a specialty tool like a die drill so sometimes a part can be saved. If there's not a lot of material in the part (cost wise) and if the machining has just started it's usually more economical to toss the part. If it's a $1000 USD piece of material with a few hours of machining already done that's a different story.


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## kaichu dento (Apr 5, 2012)

Just tried to send you a PM and noticed you have no contact info I could find. Wanted to send my V10R Ti to you for a job we talked about a while back so if you can send me a PM with your address I'll get it in the mail tomorrow.


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## precisionworks (Apr 5, 2012)

kaichu dento said:


> Just tried to send you a PM and noticed you have no contact info I could find. Wanted to send my V10R Ti to you for a job we talked about a while back so if you can send me a PM with your address I'll get it in the mail tomorrow.


Sorry, my PM's are turned off. Please click on the website link in my sig line for the email address.


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## kaichu dento (Apr 5, 2012)

precisionworks said:


> Sorry, my PM's are turned off. Please click on the website link in my sig line for the email address.


Great - I'm heading to town and putting it in the mail!


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## precisionworks (Apr 5, 2012)

kaichu dento said:


> Great - I'm heading to town and putting it in the mail!


Good timing - Kyocera just sent some cermet test inserts designed for titanium machining. One is a strong negative shape used for roughing & the other is a fine tipped finisher. Hope to finally get more than a few minutes per insert.


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## precisionworks (Apr 22, 2012)

The Kyocera cermets are holding up well & giving more than twice the life of the coated carbide insert that had been used 

One other factor that has helped extend the life of the super-sharp finishing inserts is reducing the speed. I'd been running at what I thought to be a conservative 105 sfpm & getting short tool life. Dropping the speed down to 73 sfpm has more than doubled the life of those fragile inserts. There's nothing else that will get into the tight root transitions when profiling a shape like this:







For the final finishing pass the lubricant is shut off & the part is run dry. The reason for this is that a 4X magnifier is used while advancing the tool & the magnifier does no good when the titanium surface is covered with oil. Depth of cut on the final pass is around .003" (.08mm) & the tool will tolerate running dry at the slower machining speed.


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## precisionworks (Jul 9, 2013)

Just a few more thoughts on this topic ...

Coolant/lubricant is essential on for 6-4 work. With the correct choice of insert & coolant speeds of 100 sfpm & more are possible. Without coolant speed must be cut in half & insert life is much shorter. 

Drilling & tapping are done at slower speeds than turning or boring. When installing McGizmo Ti clips (using a 4-40 thread) my normal spindle speed is 800 rpm & that equals 18 sfpm. A solid carbide 142° spotter drill is used first, then a solid carbide 140° tap drill & finally a powdered metal cobalt tap cuts the threads. Threading tables give drill sizing based on a 75% thread but 6-4 titanium taps more easily at a 60% thread ... 95% as much strength & a lot less tap breakage. 

Grooves shown below were cut with a full radius form tool. Form tooling generates more heat than a shearing cut & also tends to induce chatter, especially on springy materials. Part was run at 75 sfpm for grooving.


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## wquiles (Jul 10, 2013)

The moment I got paid to do machining work 4-5 years ago I became a machinist. Not the same as being a good machinist, but still, I "do" consider myself a machinist, even if my work capabilities/envelope are still rather small. I know what I can do well today, but I also know I have a "lot" more to learn.

I have slowly been getting better with help of my machining mentor (Barry), and several other folks (most from this sub-forum - Daniel, Will, etc - too many to name individually), but I got to tell you: the most significant improvement in my machining has come when I finally bit the bullet and started working with Titanium. Man, working with Aluminum, Brass, Delrin, and mild steel was super easy - you can get away with a lot of stuff in terms of speeds/feeds/etc. In fact, I would even say that one can pick "bad" habits with the easy materials :shakehead

I have some Al-specific inserts and PCD inserts that I have used for over a year straight!. But not with Titanium - Titanium is a whole different animal, and not just on its abrasive nature, but also due to its poor thermal properties. As I told Barry over the phone a couple of times, if I can summarize my experiences so far with Titanium, I can put everything into one word: humbling.

Working with Titanium has been rewarding so far, and I look forward to learning more about this very neat material 

Will


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## precisionworks (Jul 14, 2013)

wquiles said:


> ... if I can summarize my experiences so far with Titanium, I can put everything into one word: humbling.
> 
> Will



Titanium is easier to machine than AR400, more similar to 4140HT. Exposed ops like OD turning or ID boring aren't bad but drilling & tapping can cause fits. Bigger drills & taps don't cause as many issues as the tiny drills & taps. The smallest I tap is 4-40 because it's tough to gauge feed pressure - continuous chip flow is what I look for. A solid carbide drill that's 2mm diameter is not hard to break


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