Quit while you are ahead!

This topic has 18 replies, 14 voices, and was last updated 20 October 2014 at 12:47 by Nigel Bennett.

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17 October 2014 at 21:57 #23544
Oompa Lumpa
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@oompalumpa34302
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17 October 2014 at 21:57 #166805
Oompa Lumpa
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@oompalumpa34302
Should also read "Don't push your luck!"

I thought of putting this in the "Hints and Tips" thread too.
Anyway, as some of you know I haven't been having much luck lately, well I have – but it has all been bad!

After the toothache fiasco (I will put that down to typical "Bloke" behaviour) then my dog ate the picture frame and a few other disasters I thought I was out of the woods.

Except yesterday the linisher bit me and removed the top of the fingernail from my Index Finger. Do you have any idea how difficult it is to shoot a competition with a Mr Bump plaster on your index pinkie? Well it isn't easy. So today passed – by and large – without incident and I thought I would do a bit of catching up. I am well behind with a few things. One of the first things I did this morning was set the Donkey (Saw to everyone else) to cutting some disks of Titanium. I needed four disks sawn 12mm thick from a piece of 40mm bar stock. Anyone who has done this knows it is going to take a while. Took up most of the day to be honest.

So anyway, I started to turn them up to the correct thickness, the first one passed without incident but setting the second one up in the chuck I (clumsy Oaf) clipped the chuck with the insert and chipped it. As it was only a small chip(?) I decided it would do for the next cut.

There are certain things you learn when working with Titanium and one of those things is to keep all the trays clear of Swarf. DO NOT allow it to accumulate. Why? Because if (when) you have the swarf light up because you are using too much pressure on a cut that is too big for the chipped tool you are hell bent on getting your full value from, you won't destroy the machine. It is just not possible to put a Titanium burn out with any sort of home extinguisher. I know of one person lost a Bridgeport

This is the bit that lit up coming off the tool, it was definitely one of those "Full Pucker" moments:

And this is the swarf I had just cleared from the tray:

It could have ended in tears. Instead I decided to turn the lights off and go make some tea. Far less risk.

graham.
18 October 2014 at 01:31 #166823
Bill Pudney
Participant
@billpudney37759
A good leave!!

A mate of mine makes dental implants from Grade 5 Titanium. So they are very small, nothing much bigger than 6mm diameter. He is very, very careful to clean up the swarf after every part. Marginally less exciting than magnesium!!

cheers

Bill
18 October 2014 at 05:08 #166828
thaiguzzi
Participant
@thaiguzzi
Yep, magnesium is THE ONE. Panic stations when that catches light. Only ever happened to me once, hopefully never again. Thing is, magnesium machines beautifully, whereas Titanium is a pig to drill and mill and saw, and only slightly more fun to turn.
18 October 2014 at 07:32 #166832
Boiler Bri
Participant
@boilerbri
We make filling nozzles from grade 2. Never had any reports of it lighting up from the machine shop.

We then TIG weld the assemblies, never had a problem here either! So is the grade 5 different.?

Bri
18 October 2014 at 09:44 #166840
Oompa Lumpa
Participant
@oompalumpa34302
Grade 5 is no different than Grade 1 or 2 or indeed any of the commercial grades in it's ability to light up. I was pushing my luck with a damaged/blunt tip and no coolant. Flood coolant is highly recommended and it is something I just don't have at home (nor will I for as long as I can do without) AND as you can see from the remnants I was taking a heavy cut = Lots of Heat.

I would have to take advice on the welding bit as to why it doesn't ignite, I just don't know. I will finish the bits off today, using a sharp tip and put a pic up – I just don't need any more drama

graham.
18 October 2014 at 09:56 #166843
Ian S C
Participant
@iansc
Graham, I did say brass would look quite good. Didn't actually know that Titanium was inflammable. I suppose the reason it doesn't burn when it's being welded is because the oxygen is eliminated by the heat.

Ian S C
18 October 2014 at 13:03 #166868
IDP
Participant
@idp
Ian S C

Not sure about oxygen being eliminated by heat, if this was the case we wouldn't need to use flux of any kind.

IDP
18 October 2014 at 13:05 #166869
Neil Wyatt
Moderator
@neilwyatt
Probably the surface area to volume ratio, there's vastly more surface are on even the small bunch of swarf than a large weld.

Neil
18 October 2014 at 14:37 #166875
jason udall
Participant
@jasonudall57142
I would suspect the presence of a gas shield present in most welfing processes. …no O2 no fire.
18 October 2014 at 14:39 #166876
jason udall
Participant
@jasonudall57142
Although try putting a magnesium fire out with co2 and you might have a supprise….
18 October 2014 at 17:14 #166893
John Durrant
Participant
@johndurrant47282
Odd this!!

I worked at Rolls Royce for 8 years, machining parts for the Adour Jet engine (for the Harrier). Machined quite a lot of titanium for various parts. Never once had a fire, and never even heard anyone mention that it was a possibility.
18 October 2014 at 17:45 #166897
mike T
Participant
@miket56243
If you take some fine steel wire wool (or a birdsnest of fine dry steel swarf) and tease it out slightly; It will burn spectacularly if you put a match to it. I am sure the same would be true of most finely divided metals and some non metals, non of which you would consider a fire risk in bulk form.

Flour dust and coal dust have produced very damaging explosions in the past. Aluminium powders are used in underwater explosives (torpex) and titanium powders produce the intense sparkle in garden fireworks. It is all to do with maximising surface area in the presence of an oxidiser (air) then raising the temperature sufficiently. So keep it tight and keep it wet and you reduce the risk significantly. And remember not to throw that dogend into the swarf tray.

Mike
18 October 2014 at 18:00 #166899
martin perman 1
Participant
@martinperman1
My first job was a machine tool fitter for Lucas CAV in Sudbury and in our fuel filter manufacturing plant we had to constantly clean the services, pipework etc in the roof space otherwise flash overs were regular from paper dust created by making the filter rolls.

Martin P
19 October 2014 at 15:59 #167024
neville rigg 2
Participant
@nevillerigg2
Hi all, I worked on the installation of a extrusion press for use with magnesium a d the safety lecture was go nowhere near it with water, only sand in case of a fire and call the fire service.

Neville
19 October 2014 at 16:19 #167027
Trevor Wright
Participant
@trevorwright62541
Set fire to a lathe in exactly the same fashion as Graham first time machining Titanium. Thought it was quite pretty when the swarf was igniting until I realised the swarf in the tray was going up – luckily had flood coolant going and doused it. Taken more care and kept tools razer sharp ever since.

Have seen Titanium welded and can only assume the lack of Oxygen prevents ignition, or maybe the swarf was getting hotter than the temperature used for welding.

Trevor
19 October 2014 at 21:13 #167052
Oompa Lumpa
Participant
@oompalumpa34302
The hazards of Titanium are well documented and I really should have known better. I have machined (not massive amounts) quite a bit of titanium over the years and never had a problem. As Trevor had noticed, the swarf in the tray will go up once it starts and I do tend to clear it as I go along, in this instance the only swarf in the tray was the bit that went up.

And I don't care how fast you think you can move, when it lit I was mesmerised like a bloody snake! The reason for this conflagration was simple – a blunt tool and a good deal of pressure on a big cut. As I was having to force the cut I just knew it was wrong and I should have backed off but it was late and I wanted to get finished. You know how it is.

Anyway, no harm done and if this is a caution to anyone machining this stuff then that is not a bad thing at all is it?
And the bits are all finished now

graham.
20 October 2014 at 12:24 #167117
Ian S C
Participant
@iansc
As Neville says, sand, those old enough, or your parents will remember sand in a bucket for putting out incendiary bombs during WW2.

Ian S C
20 October 2014 at 12:47 #167122
Nigel Bennett
Participant
@nigelbennett69913
Apart from the relatively huge surface area of swarf, it's also likely that there will be no oxide coating on freshly-removed swarf, so that the surface is more likely to be reactive. Oxides on the surfaces of bits being welded together would therefore be unlikely to ignite easily – as has been discussed.

John Durrant's comment about the Adour in the Harrier is puzzling – I thought it was a Pegasus in there. Mr Wiki says the Adour was used in the Hawk and Jaguar.
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