Machining Titanium on a Hobby Lathe. Is it a good idea?

[Nick HulmeParticipant @nickhulme30114]

Posted by Andrew Johnston on 18/12/2016 21:44:25:

However, you're right about not listening to the armchair experts – which is why I don't take any notice of you.

Andrew

Just for you I've taken and added a photo to my album, not being self-absorbed most of what I do goes undocumented but I recommend you don't work Titanium from your armchair as you don't have the correct extinguisher and won't spring for one 😀

[Neil LickfoldParticipant @neillickfold44316]

From my experience in Ti turning and drilling, there are plenty of warning signs that things are not going well. Way ahead of any fire type situation happening. 1st warning sign is that the workpiece is getting hot, with water based coolants for Ti, you will see that there is steam coming off the work piece. That tells you right away that the tool is dull or you have the wrong feeds and speeds, or the wrong geometry for Ti. There are loads of drills and various turning inserts specifically for turning Ti and they cost about the same as regular general turning inserts, if you buy from a supplier that has clients using them. The highest risk times is drilling and parting off. It seems that most problems in drilling is a dull drill, and too high a surface speed and too slow a feed rate. Parting off issues occur when the tool starts to get dull at the end of cutting off a part, and not realising that it was dull to be cutting the next part. Having a chart /record of how many parts you make before tools dull off is the most valuable info that the books don't have. I use grade 5 and 23, 23 is 5 with low oxygen. Ti-6AL-4V Ti64 as we call it. Neil

[capnahabParticipant @capnahab]

I agree with the warning signs, once you have seen them it is clear whats going to happen. The tip of this HSS tool was too small and caused the fine stringy chip to heat up. Heres how not to do it.

 

 

 

 

Edited By capnahab on 05/02/2017 20:32:12

[Neil LickfoldParticipant @neillickfold44316]

What Diameter is your work piece in the video? What RPM did you have it running at ? I turn on the myford at about 16 to 20 m/min as a surface speed, so if it was a 1 inch bar, would be about 200 rpm with coolant. Without coolant I use 10 to 12 m/min . With a .2mm radius tool, I use about 4thou per rev feedrate. Ti is a very poor conductor of heat. So dull tools heat the work piece and the heat becomes more local . In turn it work hardens the immediate cutting zone.

Neil

[Neil LickfoldParticipant @neillickfold44316]

So I recently drilled a 3.2mm hole through some 3d printer Ti heat breaks. I drilled them at aprox 350 rpm with a Ti milk coolant. Feed rate is about .05mm to 0.1mm per rev, so similar to drilling stainless steel. All went very well using just a normal New HSS drill. 10 were made and they are only 19mm long though. Fires occur when you get things out of control , ie it gets too hot from dull tools or wrong feed/speeds. Ti coolant is Chlorine free and I mix with rain water.

Neil

[Mick B1Participant @mickb1]

I've been machining titanium for a few years on a hobby lathe, then heat-treating it to bright blue with a butane torch, and it never occurred to me there was a fire risk. So far as I know, none of my workpieces or swarf was ever near to catching fire.

The stuff is tough, and I think that's why the swarf parts relucantly and with a fair amount of heat from its parent stock. But with a sharp HSS tool and a lowish speed, you can dig deep and peel away lots. Most of what I do with it is decorative rather than functional, and I'm quite happy to use HSS – carbide doesn't seem justified.

Blue items are titanium, the others PB102; all done on a Warco WM250V and a Sig C0. No coolant apart from the odd squirt of WD40:-

[John HaineParticipant @johnhaine32865]

A few years back there was a series of articles in HJ describing a clock using titanium for the escapement wheel for low weight, by Dick Stephens. As far as I recall he was using conventional tooling, may be worth looking up?

[David George 1Participant @davidgeorge1]

I have machined titanium spacers for hot runner systems for many years they are supplied over size and have to be machined ,mill, turn, and grind to size to suit. They are used to prevent heat transference to the body of the tool in plastic mould tools and as long as plenty of coolant is used no problem. The only time i saw it burn was when a cleaner desided to set fire to some rubbish in a small skip containing swarf which had some titanium as well as other metals as well, water put on by fire brigade caused a flare up and they just let it burn out keeping the building cool.

David

[Neil LickfoldParticipant @neillickfold44316]

To turn the Ti Blue, get Diet Coke or Pepsi, place the item in the jar and put about 36 to 48 volts across. It will colour change. The voltage give a particular colour. So have a play and you can make different colours.

Cant remember if the wire in the fluid is +or –

Neil

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