First experience with titanium

[jhanko]

I finally got a hold of some titanium to try out on my mini lathe as I felt confident in all cutting procedures with aluminum. These are my impressions and I welcome any advice. At first I was worried that a mini lathe would not be able to do a good job with titanium. Not true. This stuff actually machines beautifully. Turning, facing and boring went great. I haven't tried threading yet, but don't anticipate any problems. The big problems I encountered were with drilling and knurling. Drilling this stuff without flood cooling seems to be just a bad idea. It took me 45 minutes to drill a 3/8" hole through 3" of stock with brand new cobalt bits. This stuff drills HOT! The bit would quickly heat up, expand and start to bind causing more heat, etc... Peck, cool, oil, peck, cool, oil... Is there any better tool or method to get through this stuff in a reasonable amount of time? I'm completely aware of the flammability of titanium swarf, so I made it a point to clean up often and take light cuts to avoid sparks. Knurling was a disaster. I couldn't get a good track with it. If I got into a bad track with aluminum, I could correct it with more infeed, reducing the diameter and get it to single track. Not possible with the titanium. Maybe my lathe/ tool just isn't strong enough to sink into this stuff. I ended up with a very nice double track knurl, but it's not what I wanted. Any tricks to this or should I just give up trying to knurl it?

 

[PhotonFanatic]

From my experience with trying to knurl Ti, you would need to use either a cut knurler, or better yet, a straddle knurler. However, I'm not sure that a benchtop lathe is strong enough, even if you were to try a straddle knurler.

Yeah, facing, turning, and even milling Ti isn't that hard. Drilling seems to be the toughest operation. What speed, rpm's, were you using and what diameter? You need to use a slow speed and moderate infeed rate, plus your drill has to be sharp.

If you go too fast when you start drilling, you will dull the drill very quickly, and things just go downhill from there.

Personally I use carbide drills that are coated to withstand the high heat that drilling Ti creates--those are made by M.A. Ford, and are fairly expensive.

I believe that others are using cobalt drills, but with coolant, and then resharpening often.

 

[Anglepoise]

Keep the feed up, and the speed down. Also on a small lathe you will have to start with a small hole and just increase from there in small increments.
Ti work hardens and that is why you need to have aggressive feed at all time.

I agree with Fred. A scissor style knurl holder is probably the best way but you might stall the motor when doing Ti.

Even with doubling, your knurl looks very nice.

 

[VanIsleDSM]

Nice, glad to know the mini-lathes can massage titanium with light cuts.

Is carbide a must for tooling? or can you get away with HSS?

 

[jhanko]

I drilled first with 1/8", then 1/4", then 3/8". Starting out at about 500 rpm, slowing down to about 150 rpm for the 3/8" bit. I had major problems with all of them. And this is with new TRW cobalt bits, not junk. Everything went alright until I got about 1/2" deep. After that, lubricating the bit becomes harder to access, friction takes over and heat becomes unmanageble. I might invest in a couple of carbide bits, but I have a feeling that constant cooling/lube is the only solution and unfortunately not an option in my case. I tried carbide inserts and HSS when turning and facing. They both did an excellent job. The whole drilling situation really sucks as it's going to prevent me from using Ti as much as I'd like to, if at all...

Jeff

 

[matrixshaman]

I managed to get some 1" diameter holes in 1/4" thick 6Al4V using some fairly cheap Harbor Freight bits and a drill press but it took a whole lot of time and lube oil. I did some other smaller holes and it is a serious PITA.

 

[PhotonFanatic]

I drilled first with 1/8", then 1/4", then 3/8". Starting out at about 500 rpm, slowing down to about 150 rpm for the 3/8" bit. I had major problems with all of them. And this is with new TRW cobalt bits, not junk. Everything went alright until I got about 1/2" deep. After that, lubricating the bit becomes harder to access, friction takes over and heat becomes unmanageble. I might invest in a couple of carbide bits, but I have a feeling that constant cooling/lube is the only solution and unfortunately not an option in my case. I tried carbide inserts and HSS when turning and facing. They both did an excellent job. The whole drilling situation really sucks as it's going to prevent me from using Ti as much as I'd like to, if at all...

Jeff

Jeff,

I recently drilled out a battery tube in 6AL4V, it was 17mm in diameter and 49mm deep, i.e., .67" x 1.93".

I start with a 5mm drill with the RPMs starting at 500, going in about 12-15mm each time, and applying some cutting fluid between each entry. Yes, the cutting fluid ends up smoking away!

Once to depth, I then switch to an 8mm drill, drop the RPMs down to 450, or so, and once again go in about 10 - 15mm each time.

To keep it short, I do the same thing with 11mm, 13mm and 15mm drills, dropping the RPMs by 50 with each drill change. Sometimes, though I find that slightly higher RPMs and a slower infeed works better. I just try to let the drill bit tell me what to do. As I am feeding by hand, I can often sense whether the bit is cutting OK, chattering, or just binding.

Finally, I bore out the opening to final size, taking many passes with small DOC.

Link to the MA Ford Twister XD drills with Altima coating.

 

[McGizmo]

I have had reasonable success using a mister for cooling and it isn't as messy as flooding the part with a heavy flow of liquid. I suspect I have done everything wrong with machining Ti that you can do. I have had a couple fires with the chips and I once pulled a cobalt bit out of a deep bore with the bit bright red and actually sagging like melted plastic!

A solid carbide boring bar can be a good alternative to drill bits if you don't have good sharp bits and the means of cooling them. I have stepped the hole sizes in some cases where I needed a deep hole and having the hole the same diameter over the depth was causing heat and machining problems. By stepped, I mean getting out to the large diameter in a hole not the full depth and then coming back with smaller diameter drills or boring bar cuts and lengthening the hole in that manner. My thinking was that this allows better access for the cooling being used as well as chip evacuation. It is pretty easy to have the chips get in the wrong place and gall with the surface beyond the cutting edge.

There are experts here on the forum and I for certain am not one of them so consider my comments accordingly.

 

[jhanko]

I recently drilled out a battery tube in 6AL4V, it was 17mm in diameter and 49mm deep, i.e., .67" x 1.93".

Just curious, how long did this take you?

I have stepped the hole sizes in some cases where I needed a deep hole and having the hole the same diameter over the depth was causing heat and machining problems. By stepped, I mean getting out to the large diameter in a hole not the full depth and then coming back with smaller diameter drills or boring bar cuts and lengthening the hole in that manner. My thinking was that this allows better access for the cooling being used as well as chip evacuation.

That's pretty much how I ended up getting it finished. I figured my best bet at getting it done was by minimizing flute contact as that appeared to be a much larger source of heat than the cutting edge. The huge problem is the time required. I mean come on, 45 minutes to drill a hole... A mister sounds interesting, even if it's just a simple pump spray bottle. Thanks!

Jeff

 

[Anglepoise]

I have played around with different lubes for drilling Ti and
have found "Anchorlube" to be very forgiving. Its water based and needs careful cleaning up for rust, ( a chore I don't mind <g> )
but is worth trying.

It is specifically formulated for SS,Ti and other hard metals.

The manufacturer has a toll free number 800 466 9925 ,US made

Below is a pic of a 1/2 inch cobalt drill feeding into a 3/8th hole in Ti.
Peck, withdraw, coat drill with 'Anchorlube', and repeat.

 

[PhotonFanatic]

Just curious, how long did this take you?

Jeff

Probably about 50 minutes total, including the boring. There's a lot of time wasted just setting up for each size drill. You really can't rush this operation, unfortunately.

 

[jhanko]

Probably about 50 minutes total, including the boring. There's a lot of time wasted just setting up for each size drill. You really can't rush this operation, unfortunately.

Good to know I'm not alone. I just can't beleive there's not a better way to get through this stuff...

 

[PhotonFanatic]

There is a better way--give it to a CNC machine shop to do. :devil:

 

[McGizmo]

There is a better way--give it to a CNC machine shop to do. :devil:

Yeah, that is what I do whenever possible! I have spent silly amounts of time slowly turning away at Ti. But even the machine shops when they have nailed down the feeds and speeds and identified the right cutting tools and geometry still take serious time in turning out Ti parts.

 

[Mirage_Man]

Ah yes, drilling 6AL-4V. That's my favorite thing in the world to do...NOT!!

Drilling ti has got to be the biggest PITA about working with it. In fact it is one of the reasons for my resolution to get a bigger more powerful machine than my Heavy 10.

The only advice I can give is go slow and if it's not possible to use flood coolant then use plenty of cutting oil. I used cutting oil for awhile before I made the flood set-up. You just have to squirt some in the hole, drill some then back out and squirt some more. Continue this process until done. It would take me approx. 15-20 mins. to get through 1.5" with this method.

Another thing, don't waste your money on a Drill Doctor thinking it will sharpen larger cobalt drills. It won't! It is a real exercise in futility. My experience is either find a shop that can sharpen your drills or invest in a real drill grinder. If you go the drill grinder route be ready to lay out anywhere from $600-$2000 or more. There are those that say you should be able to hand sharpen drills but I'd like to see someone that can put an edge on a drill like the right machine can do with a split point and the different geometries that make for a great drill.

As far as the process goes... I start out with a center drill then I use a 1/4" or slightly larger drill. Then I use whatever size drill I'm trying to drill to as big as 7/8" in some cases. By using a smaller pilot hole you take the pressure off the tip of the larger drill. What I would not do is step up many different sizes trying to get to the largest drill. I always finish up with a boring bar to my final dimension. Drilling is only a roughing operation.

The bottom line is that drilling ti is a slow process even with high pressure coolant. This is one of the many reasons that parts are as costly as they are. It is not only pricey material but it's a slow process and is hell on tooling and equipment. Cutting aluminum after working with ti is like cutting butter with a hot knife!

 

[KC2IXE]

another option, and least for the bigger bits is coolant fed bits

And I'd bet a coated carbide would work somewhat better

 

[jhanko]

Well, I have to admit that I do love this stuff, once you get past the drilling nightmare. I just bought a Nitecore piston drive light with the Golden Dragon emitter and am very impressed with it so I've decided to make a titanium body and head for it. I've been lusting after Don's Ti PD for years, but realize that I'll probably never be able to afford one. Hopefully, this will ease my craving for one. I did the head first as it seemed like the more difficult of the two pieces. It turned out great. I completely forgot that I was working with Ti and cut the threads with a straight infeed. I still ended up with beautiful threads inside and out. I did have to make about 20 passes though. Well, here's the head. I'll do the body tomorrow...

 

[wquiles]

Outstanding - nice work there dude!

 

[jhanko]

Thanks Will! I'm trying...

 

[Nitroz]

. I completely forgot that I was working with Ti and cut the threads with a straight infeed. I still ended up with beautiful threads inside and out. I did have to make about 20 passes though. Well, here's the head. I'll do the body tomorrow...

You make that look so easy.

I can't wait to see the body.