Turning / machining Aluminium – Tips

[Chris machinParticipant @chrismachin]

Hi , I've got a few bits of aluminium which i was thinking of substituting for certain components made of brass such as flywheels e.t.c. to save buying the brass. After having a go turning it i'm after some tips.

What speeds . what tools are best i.e hss,tipped tools. Do i have to use a coolant (whats best) ?

When i tried cutting it seemed to stick to the tool….

Any help appreciated

Chris.

[Chris machinParticipant @chrismachin]

[JasonBModerator @jasonb]

Alloy is not ideal for flywheels as being light weight it does not have the mass of an brass, bronze or iron flywheel. What other bits are you thinking of changing then we can advise if alloy is suitable.

Parafin is a good lubricant or pump action WD40.

HSS will be fine though you may want to grind a slightly higher top rake, if going for tipped tools then the specific alloy and non ferrous tips work very well.

J

[mike TParticipant @miket56243]

Beware of bits of aluminium found laying around. Some bits may machine well or just stick to the cutting tool.

I machine lots and lots of aluminium and I have no problems with HSS or tipped tools on the mill or lathe. I machine dry, without any coolant or lubricant, provided I use the right grade of aluminium alloy

I ALWAYS buy a known grade of aluminium. My material of choice is HE 30 TF………… 6082 T6 or T4.It machines beautifully. Do not buy anything that is "good for bending" as it will be too soft and will just weld itself to the cutting tools

[JasonBModerator @jasonb]

Cutting wet usually prevents the metal build up on the tool so you can get away with a larger range of unknown materials.

J

[Brian Dickinson 2Participant @briandickinson2]

Parafin is the best lubricant for machining ali.

Reasonably high cutting speeds.

Dead sharp tools.

Watch out for ali with hi content of magnesium or you may end up with a hot workshop!

Bri

[JonParticipant @jon]

BS1474 HE30 TF 6082 T6 will clog the cutters up if no coolant, thats all i will use as it anodises well.

6082 T6 after 3 1/2 hrs http://pic20.picturetrail.com/VOL15/728921/1252422/393696139.jpg A mister you wouldnt be able to do 1/8 that in the time, ok for menial cuts. I am limited to 540 RPM or the RCCD trips on startup.

Even the free machining can clog cutters up.

[Mark Foster 1Participant @markfoster1]

try a bit of sunlight bar soap on the job works well

[Ady1Participant @ady1]

When i tried cutting it seemed to stick to the tool….

Turn it slowly enough to not generate any heat and you'll be fine, no lubrication necessary.

Aluminium is very soft

[_Paul_Participant @_paul_]

WD40 has worked very well for me as a lubricant when cutting/milling aluminium, I buy it by the gallon gallon and frugally dispense with a small poly bottle (ex SWMBO's hair dye) fitted with an old "Biro" refill as a spout.

No lubricant and I find it soon forms a deposit on the cutting tool giving a poor finish.

I have'nt seen parraffin anywhere locally for some time now and if I remember when I last bought it it was expensive, I still remember the days of filling up the old "Valor" heater with I as a kid when it was probably only coppers for a gallon.

Regards

Paul

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

Posted by _Paul_ on 30/03/2012 01:21:18:

I have'nt seen parraffin anywhere locally for some time now and if I remember when I last bought it it was expensive, I still remember the days of filling up the old "Valor" heater with I as a kid when it was probably only coppers for a gallon.

Regards

Paul

Paul and all folks, in case paraffin is not available, you can use barbegue grill igniter fluid or lamp oil as lubricant for tools on aluminium.

[JasonBModerator @jasonb]

You can get it on a lot of petrol station forecourts as well, thats where I get mine. And garden centres still have it for greenhouse heaters.

J

[TerrydParticipant @terryd72465]

I have around 1500 litres for sale (at 50p/L) after installing a Heat Source Air Pump in place of my oil fired boiler. Any offers?

Regards

Terry

[JasonBModerator @jasonb]

Think you should try and run your car on it given the panic buying

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

I would not recommend use of Paraffin as a cutting fluid . Though often suggested for this purpose in the past it is really quite unsuitable . Some reasons are :

(1) It is actually quite a poor cutting fluid – ordinary cutting oils are far better and much cheaper .

(2) It is a de-oiling fluid like petrol which dissolves and effectively removes any oil present in slideways and bearings .

(3)  The spray that comes off from any higher speed turning is dangerous to health . No petrochemical spray is now acceptable in free air environments .

(4) It is inflammable .

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Turning Aluminium is not particularly difficult in itself but it can sometimes produce seemingly vast amounts of swarf .

When turning some grades the swarf comes off in a continuous fine ribbon which can wrap around the work and more commonly produce big swarf bundles or 'birds nests' . This problem can be reduced when it happens by using chip breaker tool shapes .

—————————————————————–

Purely aside : there was along discussion in ME many years ago about Paraffin 'causing' rust . I don't see any reason why paraffin would directly cause rust but the combination of de-oiling and use of paraffin stoves probably did .

 

 

 

Edited By MICHAEL WILLIAMS on 30/03/2012 08:38:32

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by MICHAEL WILLIAMS on 30/03/2012 08:26:36:

—————————————————————–

Purely aside : there was along discussion in ME many years ago about Paraffin 'causing' rust . I don't see any reason why paraffin would directly cause rust but the combination of de-oiling and use of paraffin stoves probably did .

Edited By MICHAEL WILLIAMS on 30/03/2012 08:38:32

Hi Micheal, I've heard about paraffin causing rusts for many years, but I don't beleive there is any truth in it. As you say it is a de-oiler and in my previous employment it was used in a parts cleaner for cleaning such things as bearings and worm drives of all the old oil, grease and dirt. Steel parts would only go rusty if they were left long enough for the paraffin to evaporate, thus leaving unprotected bear steel to any damp air in the workshop.

Regards Nick.

[Brian Dickinson 2Participant @briandickinson2]

I agree with Nicholas, all the components for our label applicating machines are made from ali, well all most all.

The three engineering companies that we use all use Parafin. I even use it and as far as i am concerned there is nothing better.

The partsa re all de-greased and then anodized.

Bri

[BazyleParticipant @bazyle]

Suggestion, though I've not tried it: If you mix as small amount of Waxoil or equivalent clear car body protection into the paraffin it will leave a wax layer after the solvent evaporates.

As to people quoting specific grades have you ever seen the BS spec quoted by a Model Engineering supplier? Metal available is shiney, light grey, dark grey, yellow, and of course blotchy brown.

[Steve WithnellParticipant @stevewithnell34426]

Hmm, I'm sure there will be EN/BS comparison tables if you Google. Steels are usually quoted by "EN" which I think is "European Norm" ie standard. Ally is typically quoted by an "HE" ref by the suppliers but I don't know what that stands for. Cast Irons I think are usually referenced by "CR". All the suppliers I've seen do sell by the specification label, not by colour splash. (On larger diameters I usually write in big permanent marker "30" for HE30 or "8" for EN8 and so on, as on first cut, the colour splash is lost.

End of ramble.

Steve

[Anonymous]

Here's my take on machining aluminium. It can be summed up like this:

1050 – pure aluminium, absolutely horrible, worse than copper, might as well try chewing gum

All the aluminium alloys I've machined (2014, 5083, 6063, 6082, 7075) were straightforward

For specific operations this is what I do:

Turning: I turn dry, with a special light alloy insert from Greenwood Tools. I run the lathe as fast as it, or the workpiece will allow, with a least a 4 thou/rev feedrate. I rarely get problems with built-up-edges on the insert. HSS also works well, provided the tool has a decent rake angle, is sharp and is smooth (I use diamond hones after grinding). The main issue is making sure the swarf doesn't end up as a birds nest.

Manual Drilling: No problem with HSS drills, I use WD40 to stop clogging of the drill flutes

Manual Milling: I don't do much of this, but when needed I do it dry. I have had a few issues with HSS cutters getting swarf build up in the flutes, so for preference I use carbide cutters

CNC Milling: Flood coolant (Biokool14 from Hallet Oils), mainly to get rid of chips with both HSS rippa and uncoated carbide mills. I run cutters fast, for example a 6mm carbide slot drill will run at 4000rpm

Best Regards,

Andrew

PS: Bazyle – I know I've quoted various specification numbers, but then again I very rarely buy metal from ME suppliers, because you haven't got a clue what you're getting. I prefer to use commercial metal stockists.

[JonParticipant @jon]

Think if you find it builds up with hss, it will build up with carbide. Its the heat generated so needs cooling.

Andrew i have to ask since you run dry and get no or very little build up, are you taking menial cuts?

Agree on must know what you are buying as well, it all feels different.

Birds nest, haha i should do a video on how to avoid or reduce but assume it wouldnt go down well. Want the job done quick no time to keep stopping and starting literally every few seconds.

The problem with drilling alums is again heat build up. If no coolant the deeper the hole the more heat generated and doing so sticks to any cutter.

[Anonymous]

Jon,

No need to be insulting; menial indeed!

I assume you actually meant trivial, as in small? Depends how you define trivial. To ensure I'm not talking rubbish I've just tried a couple of quick tests on 1" diameter 6082. Running at 1200rpm (bit slow, but it is a very quiet Sunday morning here in rural Cambridgeshire) and a feed of 5 thou/rev I used a depth of cut of 0.1" and 0.2". No problems; the swarf came off in beautiful ribbons with no sign of build up on the insert. The insert wasn't new, it just happened to be in the lathe already as the last turning I did was on 6063 and delrin.

Regards,

Andrew

[JonParticipant @jon]

Not my intention Andrew far from it.

Higher spindle speed, slow feed rate and less depth of cut generates less heat.

There are many times i cant use coolant unless want a shower, i get a feel for whats happening but have to be quick. The difference here is having not by choice to run up to 540rpm or RCCD trips 1 in 3 times at 800, even worse above. Quite the opposite to you and generates heat quick with slow spindle speed, slow feed and heavy ish cut or cuts to purely get job done.

Pretty good that but what happens when you thin down shortish lengths say 1" long from 1" dia to less than 1/2" diameter?

I tend to buy specific aluminium tips most are ok until heat is generated. The exception is my larger boring bar, it dont want to know unless removing up to 10 thou then its dodgy. It thrives on coolant even when job is cold.

[Anonymous]

Jon,

No problem, it was a tongue in cheek comment.

As it happens the stock I turned started off just over an inch in diameter, so after a depth of cut of 0.1" followed by 0.2" it ended up about 0.5" diameter. Total length of cut was about 1", again by chance. Seemed to work fine, although if I was turning to a specific diameter I'd have taken a third lighter cut before measuring for the final 'to size' cut.

Regards,

Andrew

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