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  #1  
Old 03-11-2012, 11:35 AM
carp carp is offline
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Default A question about turning aluminium

So yesterday i got finally got a lathe and today i had my first go on it, i was making some rollers for my excavater tracks, anyway it took me about 3 hours to turn out 1 roller which seemed a bit slow to me, anyone got any tricks to make it a bit faster? was running at 125spindle rpm mainly because it was all new and didnt wanted to smash anything in the machine.

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Old 03-11-2012, 11:41 AM
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Default Re: A question about turning aluminium

what size machine ? how deep of cut ? type of tooling ? how much detail ? Pics?
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Old 03-11-2012, 11:44 AM
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Default Re: A question about turning aluminium

hmm size its 1190 x 560 x 460mm and 750w motor, was cutting to about 12mm and using the carbide tipped tools thati bought with it, didnt take any pics because it wasnt that impressive for 3hours work
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Old 03-11-2012, 02:07 PM
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Default Re: A question about turning aluminium

Hmm , well your definitely not going to take 6mm off in 1 pass then and come back for 1 finish pass I would say your doing pretty good with what you have , and for starting out ( it seems ) with experience , comes speed and accuracy .
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Old 03-11-2012, 06:23 PM
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Default Re: A question about turning aluminium

Thinking you probably got brazed carbide tools which are just flat topped. They suck for alum, grind up some hss blanks with a nice little nose radius and high rake angle, extra sharp and polished a bit if you can.

SFM of around 200 is good for alum and hss bits. so a 1" dia would be 800 rpm. can go faster but that should be a good starting point. if you save up and buy some carbide insert tooling someday with alum specific inserts can push well over 1k sfm.
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Old 03-12-2012, 02:30 PM
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Default Re: A question about turning aluminium

thanks guys, today was better was managing to make 1 roller every 30 minutes or so,i was quite happy with that, Pugs you are correct they are brazed tools, they seemed to go blunt quite easily and i had to keep sharpening them, i am going to look into getting a set of hss tools.
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Old 03-13-2012, 12:02 PM
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Default Re: A question about turning aluminium

Yep, hss tools are the best for aluminium, the carbide ones tend to gouge it out rather than remove material by cutting. Watch out that the ally does not attach itself to the end of the tool if you feed it too fast, several light cuts are better than one heavy cut , in my experience.
My lathe is an EMCO Unimat 4 which forces me to treat it gently because its only small.

Last edited by uk trucker; 03-13-2012 at 12:05 PM.
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Old 03-16-2012, 12:49 PM
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Default Re: A question about turning aluminium

What does SFM stand for? I gather that it is referring to a feed rate, but what does the abbreviation actually mean.
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Old 03-16-2012, 12:56 PM
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Default Re: A question about turning aluminium

http://www.google.com/url?sa=t&rct=j...IsL7PqOLb5_D-Q

Here is a post from another forum describing it:
Cutting Speed or Surface Speed

Cutting speed and surface speed are terms interchangeable in their usage. These terms and their intent are often misunderstood. To help define cutting speed I will use an illustration.

You and a friend are driving down the road. Your friend reaches into the back seat of the car and picks up a large tool bit. He then takes the tool bit and jams it down through the car’s floor and into the pavement below. As this tool bit is carving up the road like a plow he asks you what the cutting speed is. You look at the speedometer and say "One mile per hour." That is the speed you are moving over the surface and therefore represents the idea behind cutting speed.
So the definition of cutting speed is how fast the tool is traveling through the work while making 'chips'.

Revolutions Per Minute
We need to make the transition from straight line speed to rotational speed because in lathe and mill work we deal with rotation. In the lathe the work rotates; however on the mill the cutter rotates. Diameter and Pi are the factors equating revolutions per minute with straight line Cutting Speed.
Cutting Speed terms are in feet per minute while bar stock and milling cutters are in inches. We can use twelve to convert feet to inches and three to approximate Pi. The formula for RPM is then four multiplied by the Cutting Speed divided by the diameter of the work or cutter being used.

RPM = 4 x CS / Dia.

Look up metal cutting speeds in available reference tables and then experiment to optimize them for your production.


Something Interesting!

One Mile per Hour The speed of an automobile traveling sixty miles per hour equals eighty eight feet per second. A reasonable cutting speed for mild steel using a High Speed Steel tool bit is near eighty-eight feet per minute. Since eighty-eight feet per minute is sixty times slower than eighty-eight feet per second a tool bit cutting mild steel is only traveling one mile per hour.

Cutting Speed is Not Cast in Stone
The actual values for cutting speed are only possible starting points and should be verified by experiment depending on the job. A common consideration for establishing cutting speed is the time it takes to dull a tool. It may be more profitable to run faster for higher production and replace the tools more often. The other way might be to run the tools more slowly for endurance and machine unattended. There is a big variation here so after selecting a starting speed tune it up for the work to be done and the desired productivity.
Increasing the cutting speed from below two hundred surface feet per minute to somewhere above, most materials act and cut differently. A soft aluminum casting run slowly can get gummy and the tool will cut tearing its way along. However if machining at a higher speed, you can't hardly go too fast in aluminum, a cast surface may smooth out and shine like a mirror.
In most applications cutting tools do not have to attain the recommended cutting speed to work properly. A one sixteenth inch end mill would need very high RPM to cut brass or aluminum. It's really the chip load and depth of cut which for the most part makes a tool work effectively.

Last edited by 9W Monighan; 03-16-2012 at 01:05 PM.
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