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

Having an idle moment, a bit of curiosity, and the need to face a titanium bar I thought I’d answer the question with regards to the possibility of doing this in a hobby lathe. As you will see from the end of the video, the fire risk is certainly none trivial. This was a controlled experiment, but if you are considering doing it yourself I’d certainly recommend watching this first.

David

Personally, I'd use coolant but otherwise I don't see a problem. Yes, it will burn under a blowtorch but I would hope that no one would get it that hot during machining.

Without non-water bearing coolant machining mag-alloy can cause some equally brown trouser moments too.

I turned down a job involving machining titanium because of the fire risk. As far as I'm aware the fire extinguisher needs to be class D, specifically for metal fires. And that was going to cost £200.

Andrew

I regularly turn Titanium dry with carbide insert tooling, if you crank up the speed and feed too far you can cause a fire, if you avoid large buildups of swarf under the work and use common sense with your feed & speed you will not have problems.

On the other hand why not listen to those who have not had any actual experience machining Titanium, Google it a bit and then go with the alarmist Bla-Bla-Risk, Bla-Bla-Scary, Bla-Bla-Bla-Expensive, Bla-Bla-Extinguisher, Bla-Bla-Bla approach and not bother?

I'll quote you for it, it's a piece of piss :D

- Nick

Nick: Commonsense dictates that it is prudent to assess the possibilities and be properly prepared for all eventualities, however unlikely.

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

Andrew

As with magnesium, feather-fine shavings and dusty-fine particles of titanium will ignite more readily than serious-size chips.

Also as with magnesium, letting dull tools rub is a good way to start a blaze.

Best to keep coolant running and keep the heat down.

I am ignorant on this subject - I have some titanium stock that I have not yet machined. I know the dangers of magnesium fire wise but was unaware that titanium posed a similar risk. Will titanium really burn as hot and brightly as magnesium? -----Rik

A friend of mine used to run a business making dental implants from grades 2 and 5 Titanium. He had three (!!!) Schaublin 70s, which with a 70mm centre height makes them smaller than a lot of hobby lathes. He didn't use any coolant, but did use warm coconut oil as a lubricant when cutting threads. The biggest part he made was probably about 13mm long by 5mm diameter. Obviously the swarf load wasn't huge. For what it's worth he used HSS tooling, and was very careful to keep a really sharp cutting edge

As far as I know he didn't have any problems with fires.

cheers

Bill

Before i got into this hobby I did buy a piece of titanium sheet for a project. I was getting no-where cutting it with the tools I had then and hit it with my angle grinder (in a garage full of woodworking shavings and sawdust). Cutting it was even slower going with the grinder and by the tiem I;d gone an inch along (2-3mm thick) the edges were dark blue- black. Lots of sparks as you'ld expect off an angle grinder but no fire.

However having read up on cutting titanium after the event I wouldn't go that route again.

Its certainly possible to turn Ti in a hobby lathe , the most important rule is the tool whether carbide or HSS must be sharp and use speeds and feeds a bit slower than you would for tough steel , drilling needs care as a dulled drill used dry can melt and end up welded into the hole but use a new drill with plenty of coolant or neat cutting oil and it will cut ok , tapping a thread can also be difficult , you will probably find most of your home workshop taps wont even touch it and if they do will make a tortured creaking noise if they do manage to cut , but there are specially ground taps available which cut it pretty easily, ive made loads of parts from 6al4v and 6242 alloys for motorbikes ie nuts , bolts , spindles , spacers etc and also the displacer pistons and cylinders on several of my hot air engines so do have some experience.

Geoff

The only tricks I know of is to keep it cool cutting. Ie slow surface speeds, high feedrates relatively . I treat it like stainless steel, so 1/2 to 1/3 the speed of steel but 2x the feedrate of steel. It very quickly work hardens, and I find that a geometry for cutting Aluminium works really well. There are Ti specific cutting fluids , in both neat oils and soluble oils. Carbide Ti geometry drills are really neat, but expensive of course. The coated drills last quite along time. If they are resharpend, they really are the same as a std HSS or carbide drill, once the coating has gone. When tapping, sharp taps are best. I find using series taps are better than regular taps. I find that if you keep going slowly it works better than start stop approach. Series taps are smaller in the overall diameter, and you tap in a series of sized taps. Or I have ground down the outside diameter of the tap, and then relieved the od of the tap to the cutting edge. House keeping ie tidy as you go with the chips in the tray is essential.

Neil

Nice video David - especially the music. I have only ever had a fire with HSS tooling when the tip was very sharp and heated up (on a light cut ) and ignited the ribbon. Never with dry carbide tooling and I agree with Nick Hulme, take it easy.

Edited By capnahab on 19/12/2016 12:39:13

You could turn titanium with positive rake carbide tips on a small machine, I can't see how that would be a problem. Just careful not to get too carried away with the cut and keep the speed up on variable DC motors to get the torque you need. You might get blue chips flying off it so you'll need to be careful. Coolant is recommended!

The answer is most definitely yes if you come prepared with the tooling. Video shows a 1.27mm cut on titanium with a sherline lathe, and a 1/4" HSS tool.

This video comes from a very interesting article written on behalf of sherline that I found that demonstrates this small lathe taking cuts at different materials, it gave me a very good idea of what to expect on different materials when I first got this lathe;http://sherline.com/test-cuts/

Michael W

Edited By Michael Walters on 19/12/2016 13:44:01

Edited By Michael Walters on 19/12/2016 13:47:30

Andrew,

I salute you, it's rare for someone to be so aware of their own limitations, but don't assume that yours apply to others, just because they lack your need for approval which dictates the posting of a shed load of photos :D

- Nick

Wow. This forum is about sharing stuff.

Steve

At my last employment I was involved in refurbishing a Wadkin TCD CNC plano-mill that had experienced a titanium fire. The machine was drilling deep holes under flood neat cutting oil & the cause of the fire was suspected to have been a bit of swarf getting trapped between the drill shank and the component. Friction caused the trapped swarf to get to glowing hot, but it didn't start to burn until the drill was retracted from being submerged in the cutting oil & the glowing metal came into contact with air. When it started to burn, it ignited the cutting oil. This set fire to a fume extraction hose & the burning hose fell onto the hydraulic tank & set fire to the hydraulic hoses. Unfortunately. the main electrical trunking to free-standing electrical cabinets passed behind the hydraulic tank & the wiring was badly burned. As the machine was under power, the damaged wiring connected high power circuits with control circuits & damage was done to the control system. The machine required a full rewire & replacement control system, as well as a full clean down & re-paint and a replacement hydraulic tank & hoses.

While I have no need to machine titanium at home, should I have to do so I would want (as an absolute minimum) a large bucket of fine dry sand to hand to have some chance of putting out an accidental fire - and, in reality, that would probably not be enough. The TCD operator machined titanium extensively & had the means to control the fire to hand, but the damage done before it could be brought under control was extensive.

Nigel B

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Thanks for that link, Michael ... Impressive stuff:

I would say that Sherline sets the standard for [affordably priced] small machines.

MichaelG