Machining aluminum and heat

[Cogsy]

Hi Al,

Whilst I don't disagree with your maths, I hate maths...

An interesting discussion, but is the real question here, why does the parting tool try to bind in the groove !

You don't believe that heat is the issue, but I do based on observation.

The chuck will be much colder than the workpiece and conduct the heat away from the work reducing expansion on that side, simply because its a bigger mass than the work. The other side of the groove will be the part that is expanding towards the groove as the point where the tool is cutting is getting smaller in diameter and the amount of expansion at that point is no more than the tool cutting width.

There is also another consideration, the cutting tool is getting hotter as well, as it cuts, so theoretically the cut should be getting wider. It all starts to depend upon how quickly the heat builds up and how rapidly it can dissipate.

Truthfully, I'm not sure why the tool tries to bind in the groove. Heat may be the root cause of the issue in some other fashion, but I don't believe thermal expansion is. I can see how you're visualising the side of the groove encroaching on the tool, being that the part is expanding in every direction as it heats but it doesn't work that way. A good analogy is a bearing pocket. If we make a press fit pocket for a bearing, then heat the part significantly, it will expand in every direction. However our pocket is now larger than it was and our bearing drops in with no force required. In this case the sides of the part do not expand inward to reduce the pocket diameter.

And I agree the tool will be heating and increasing in size also, but the coefficient of expansion is far less for the tool than the workpiece (around half) so clearance should still be increasing. Doing the figures on steel, a 2mm wide parting blade will expand its width about 0.0026mm if increased in temp by 100 degrees C. Half of this expansion would be towards the chuck where the work is fixed so there could be some rubbing here, but as the groove itself has opened up, the tool should be free to flex and stay in the groove. It's my best guess that the cutting chips are responsible for the jamming rather than any expansion.

 

[deeferdog]

Personally, I think it's nerves. The more nervous I get the more certainty it will jam.

 

[goldstar31]

It's rather nice to have the turnings coming off in 'neat curly whirlies' a properly designed form tool. This, if you think about what I tried to write earlier, was what George Thomas designed.

He actually wrote about people having 'near heart attacks' by failing to copy his design

Norm

 

[fcheslop]

When deep parting or machining fins the tool needs to be parallel to the cut or as it gets deeper it will bind and generate heat and bind even more an obvious point that is often over looked. As you are trying to bend the tool
Iv used the Thomas rear post on my flexy Myford and can part 80mm plus no problems but always clock the post in if it has been removed. As mentioned in his book my tool post over hangs the rear of the cross slide as its the standard slide and I didnt want to loose to much space between the post its sort of a cantilever
Just my two bobs worth
cheers
frazer

 

[goldstar31]

Frazer
Son of B Terry Aspin has contributed the parting off sketch which has a nonchalant bloke, cigarette in hand having no problems.

So look again at the photograph of GHT in his book- complete with cheroot whilst working.

Just a thought for the other Doubting Thomas's

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Apologies about the lady with the bagpipes. They aren't the Irish ones either.
If you are in Morpeth, visit the Bagpipe Museum in the Chantry. Will Cocks FSA(Scot)'s collection is in there. He taught me model engineering amongst other things when I was knee high to a grasshopper.( 1941?)
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Best wishes

Norm

 

[TSutrina]

My ~1940 vintage Atlas bench Lathe with 1/4 Hp motor can not put out the heat to stick Aluminum unless I am not cutting the metal but rubbing it. Then I shouldn't be even using the tool bit. I would think that anyone with an engine lathe would already have a need for cooling system. Ozwes007 it is good advice and information. I never even though about sticking aluminum. The advice applies to any soft metal.

Actually I think your understanding of metallurgy is different then mine. Recall the old saying from black smith "strike when the metal is hot" And I have done cold welding of aluminum. The metallurgy meaning is that metals will weld themselves together, temperature is not even important, when they are pure, no oxides or any other contaminants. The black smith heats the metal up and puts a flux on it. The weld will not occur until the contaminants flow out of the joint which the striking and deformation of the metal causes. The deformation needed to cold weld is about 70%, at least over half. Explosive welding of aluminum to steel is cross section or for that matters any explosive wave welding which is cold welding shows what look likes waves of metal flowing and the contamination if not removed mixed into the metal.

What you are describing at the cutting edge of the tool is actually closer to spin or ultrasonic welding where again the motion causes the oxides to be rubbed off of the tool so pure metal touch each other, weld together. The freshly cut aluminum does not see air, oxygen so I can assure you no aluminum oxide exist at the point of splitting the shaving of aluminum off. The goal is to create an oxide to prevent welding which is done by the break cut into the tool. The cooled aluminum stiffness causes an gap to occur and the pure aluminum exposed to the air oxides. Hot aluminum is not stiff enough and thus stays in contact with the surface.

 

[goldstar31]

Might I correct you? My father, his two brothers and my grandfather were all blacksmiths and my father included being a farrier. He set fire to a reluctant horse as a boy in the 1914- 18 War but I digress. A Blacksmith works in iron where a whitesmith works in non-ferrous metals. However, if you are giving a lecture on smithing, the blacksmith does not use flux in joining steel. He may well use a flux when he actually moves away from the forge and anvil to do boiler smithing on dissimilar metals or perhaps sockets a wire rope- but I have wandered away too.

One thing my father did was to threaten me by knee capping if I had any stupid intentions to be a blacksmith! He was right, I did far far better than that and retired comfortably for longer than I ever worked

 

[mcostello]

I have made the best of both worlds, I made an upside down insert parting tool. The insert parting tools work well and work better when directing the chip downwards. I still would not like biting a cheroot in half while parting off.

 

[fcheslop]

Like many I had many butt clenching moments parting until I used the rear post. I suppose it all comes down to what the individual finds a way of managing with the kit they have
On industrial and tool room lathes Iv never had any problems not the case with model makers kit
Not sure about the tie in with ultra sonic welding but would like to know
I did work on and with one of the guys who invented it for Mattel to weld rather than glue the eyes together of dolls. They got the idea from another co worker who mentioned if you could shake the molecules up fast enough the material would melt this led to various circuits and eventually onto the crystal idea it also took a while to develop the tabs that are melted in the process .The patent was sold to Branson His name was Phil Morgan of the morgan press fame amongst other inventions
Cheers Norm, will have a look next time Im on Holy Island, just dont fall for the snake charmer and her friends.Thought it may have been an old mans reed
cheers

 

[goldstar31]

Mentioning fluxes, I came across an unusual slant. Even more unusual because it was a masonic banquet- in a Chinese restaurant. Three of our members- who raise llamas and alpacas- next to the other Atkinson's family farm is now selling fluorspar but not for steel making. It is now being sold for semi precious jewellery and decoration.
From the former home of one of the richest men in England to well, getting big money for what had to be sold by the ton for very little in the steel works just up the road.
There must be a secret something in that almost neglected bit of County Durham that the rest of us don't quite understand.

Ah well?

Norm

 

[TSutrina]

goldstar31, so are you telling me the "strike when the iron is hot" is a myth? Please tell YOUTUBE black smiths. Both smiths I watch tell what function the flux does. As far as cold welding and explosion welding. My name is on a patent showing a cold welded housing. To improve conduction to the heat sink a common plating in indium. We 100% plated the halves before trying to cold weld them together, failed. Metallurgist comments and experience is what wrote. I invite you to put a significant hole it it with facts of course.

 

[goldstar31]

I think that recorded history will show that the work of the smiths goes back certainly for at least 7000 years and that information of the Guilds appears in the Middle ages again.
Sort of finally, in more recent times it was a blacksmith that led the railway pioneer, George Stephenson to develop the steam locomotive. Somewhat ironically(?), the standard railway gauge of 4 feet 8 and a half inches is at least Roman and the proof lies in the Roman Wall here.

What WE are doing is creating a hobby with limited resources to emulate what was and is going on. Within the limits of what is essentially a 'home' hobby, references to what is probably happening in industry on a limited extent is interesting to some but impossible to people like ourselves with a somewhat ancient lathe - and in your case is having to ask how to do simple division in the home workshop.
If you follow the deliberations here you must notice that there is endless repetition and to make topics 'fresh' there must be some deviation and a bit of happy banter. Fortunately, we have understanding moderators who overlook most of our transgressions- or mine.
There we have it- all 70000 years of it and somewhere in the same book, the chilling stricture of 'Be ye circumspect'
Not my 2 pennorth as you will see
Norman Atkinson

 

[ShopShoe]

Interesting...........

I have seen references to "Friction Welding." Aparently there are industrial lathes that spin up one piece of metal and then press it against the (nonmoving) part it is to be welded to and the friction heats up the metal and then welds it. I have seen assemblies that look like they were joined in this way.

Of course, this is not someting that I think that hobbiests can do, but it is still interesting.

I Guess .....We All ..... Digress.

--ShopShoe

 

[goldstar31]

Laughingly , I have double distinctions in City and Guilds and am or was a Certified welder but My little lathes- and I suspect the gentleman raising the matter, his will not do it.
I did it all 35 years ago as a 'manure student'.
I got to the age of 3 or so when I could see what was going on on the anvil with Dad and his striker. I used to pee into the tempering trough as there wasn't a little ginger headed virgin boy which was the normal requirement in those far off days

 

[Philipintexas]

"industrial lathes that spin up one piece of metal and then press it against the (nonmoving) part it is to be welded to and the friction heats up the metal and then welds it"

I had the pleasure of touring the GE aircraft engine shop near Wilmington, NC. They have a huge lathe to join the numerous stages of jet engine compressors this way. When it hits, at surprisingly slow RPM, but with tremendous pressure, it sounds like the most disastrous machining “crash” you ever heard.

 

[Ironmanaz]

I used to friction (inertia) weld on a turret lathe. It was a wheelchair accessory, with a ball joint. The balls were about 3/4", & the shaft 3/8".Chuck
the ball, drill hole, index turret (rod in holder ), spin the chuck up & cut the power as you cram the bar into the hole, You can see the weld absorb the inertia from the flywheel (chuck). Material was 303. not a welding grade. If you try this,use the biggest chuck!

 

[ALEX1952]

Friction welding used in manufacturing does not normally use a lathe as we know it, it is a very specialized piece of kit, it may look like a lathe but that is where any similarity ends.
To weld it has to get the parent metal to melting point, lots of sparks etc and given enough time to fuse together whilst rotating in opposition, then either one of the chucks releases slightly or the machine stops, if this is not done the integrity the joint will be compromised because you have twisted the joint once it has started to freeze. high pressure is maintained during the freeze cycle, sounds long winded but takes seconds. The advantage of this method is if done correctly the material will fuse across the whole joint face with no occlusions. We used it to join two pieces to form the Rotor in a diesel fuel injection pump, saving a heck of a lot in material and improving the granular structure of the component very similar to a forged item.

 

[Jennifer Edwards]

Cogsy

When I was in my late teens I worked for Airlite Aluminium in Kearny N.J. A division of American Modern Metals.

They did a lot of aluminium drawing. We had huge drawing benches several hundred feet long. We made a lot of very heavy walled aluminium tube and pipe.

One of our customers products were aluminium baseball bats.

The large end was formed by taking a bat blank that was open at the top, just a piece of tapered pipe, and spinning up a somewhat heavy chuck in a lathe that had a half sphere form attached.

The bat blank was mounted in a fixture that had a hydraulic ram affixed. It would simply jam the pipe into the slowly rotating half sphere. The heat did a wonderful job of forming the end and smearing the soft metal.

When the process worked properly the end of the bat when sawed in half had even thickness and was quite solid (non porous).

A good operator could make two or three a minute.

Aluminium is an amazing material to work with, quite plastic even at relatively low temperatures.

With parting on my little 7x12 lathe: I just make sure my knife is properly sharpened and centred in its holder, tighten down the top slide and cross slide gibs, use plenty of cutting oil, and part away, I rarely encounter an issue unless I get over zealous on feeding the tool into the workpiece.

The few times I have experienced a jam have always been when downward pressure on the tool caused my cross slide to dip off Center causing the tool to bite in,

I do not think thermal expansion is a factor at all.

Jenny

 

[chrsbrbnk]

I always assumed it was welding on to the tip of the cutter, after the tool broke off it always looked that way

 

[BaronJ]

I always assumed it was welding on to the tip of the cutter, after the tool broke off it always looked that way

Hi Chris,
Thinking about it you are probably right ! That is one thing that I didn't think of.

Usually the tip has broken off and disappeared into the chip tray before I've had a chance to examine it.

Thanks: