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question about parting aluminum
February 12, 2012
10:45 PM
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Rob
Upstate New York
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I'd give a rear-mounted parting tool a try but I haven't seen plans for one or one that you can buy.  Besides that it's been a very long time since I've seen a picture of one for any kind of lathe.

 

Mikey said:

I must sound like a broken record about this but a rear-mounted parting tool holder is the way to go on a smaller lathe in my opinion.

February 12, 2012
10:39 PM
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Mikey
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Hey guys,

I must sound like a broken record about this but a rear-mounted parting tool holder is the way to go on a smaller lathe in my opinion. I routinely part stuff from 0.124″ to 1.25″ in steel, delrin, aluminum and brass with a P1N (0.040″ thick) parting tool at speeds about 2-3 times higher than normal turning speeds. I have parted 2″ steel with a P1 (1/16″ thick) tool at about 1200 rpm and sliced it clean. My tool holder automatically aligns the blade perpendicular to the work and the blade can extend enough to part a 2-3″ piece and remain on the centerline. I agree that parting close to the chuck is best but sometimes you just need to part somewhere that is not close to the chuck. In those cases I use a live center to support the work until shortly before completing the cut, then I remove the center support, slow down a bit and catch the part as it comes off.No problem.

I won't go into all the reasons why a rear mounted tool is better but if you haven't tried parting off from the rear you might consider it – it will make all your parting issues go away.

 

Mikey

February 11, 2012
11:05 PM
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Rob
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How many of you who having trouble parting off are using a mini-lathe?  My HF 8×12 parts off like it's cutting butter.  My 7×12 has a horrible time. I've found that this helps:

A sharp good quality blade

Blade perfectly perpendicular to the work piece

Blade not extended more than it needs to from it's holder

Compound cranked to the right so the blade is over the middle of the carriage.  You don't want it hanging out on the end of a long lever arm that will allow it to bend, twist or vibrate more easily.

Carriage locked in position so it can't move

LOW RPMs – it seems like you have to almost scrape the metal off

Advance blade slowly and carefully.  Don't rush it

Lots of lube/coolant

February 11, 2012
6:34 PM
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706jim
Thunder Bay Canada
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February 11, 2012
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Whatever tools and parameters you use, make sure that the work is securely held in the chuck and that the tool is as close to the chuck as you dare. I wouldn't try parting more than 1 x diameter away from the face of the chuck.

For deeper cuts, you can square up you parting tool with an indicator to prevent binding.

Agree with others that HSS is your best bet as it can ground to a razor sharp edge. Expect a “dished” part if the tool isn't really sharp.

April 28, 2011
12:13 AM
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jposey
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I agree! It is all about your tools especially the parting tool and the lathe. Nice post here. Very informative. I found bunch of information here.

June 28, 2010
1:51 PM
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elizme
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Thanks so much, everyone!  I think I have what I need 🙂

June 28, 2010
12:27 PM
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Rob
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That was some excellent advice Mikey.

Elizme, I'm also curious about what kind of lathe you have.  I have 7×12 mini-lathe and many people complain about it's ability to part off.  I've had good results with mine, but I probably do it at lower RPMs than most others and I take my time.  I also use a sharp high quality HSS blade and lots of lube/coolant. 

June 28, 2010
6:36 AM
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Mikey
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Hi Elizme. In order to give more useful advice you need to give us a bit of information, such as:

  • What material are you working with?
  • What kind of lathe are you using?
  • Dimensions of the workpiece and your required thickness you are trying to part off.
  • How rigid is your parting tool setup? Is it a rear-mounted cutter?

In general, parting off most materials is a routine procedure but it can get tricky when parting thin parts on large diameters. I have found that rigidity of both the workpiece and the cutter is important, as is the right speed and a positive feed. Aluminum can be parted fairly thin, on the order of 0.025″ thick, but to get that without any distortion requires careful work. Thin work also requires a freshly sharpened cutter, preferably HSS. If your workpiece is 3/4″OD or less then a 0.04″ thick cutter should work well. If greater than this then you need to go with a thicker parting tool. Again, this is related to rigidity in your setup. You will find that a rear mounted parting tool (cutter mounted upside down) is more rigid than a front mounted cutter and is the way I prefer to part off. Be sure you lock your carriage before starting your cut. Finally, you need a lot of coolant when parting most metals, including aluminum. I find A-9 to be the best for critical cuts, while WD-40 actually works quite well for most cuts in aluminum.You don't have to flood it but do not let the cut go dry.

You may also want to try some trial cuts before commiting to cuts on a piece with a lot of work in it so you can nail down your speed and feed. As I said above, a positive feed is very important; you are looking for a continuous ribbon of material coming off throughout the cut.

Finally, as the cut progresses the SFM is dropping and you may need to increase speed a little or decrease your feed to avoid taking too deep a cut. Watch your chip, listen and feel the machine; it will tell you how the cut is progressing.

Hope this helps,

Mikey

June 26, 2010
10:06 AM
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Rob
Upstate New York
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I think the minimum thickness you can part-off is going to depend on your lathe, your parting tool, your skill, and the diameter of the work piece.  The best why to find out is to try it.

If you can't get the desired result by parting then what I'd do is this: Part off the piece thickier than you want it. (I might use a bandsaw if I were making a lot of parts because it can be faster than parting and the kerf is thinner).

Then I'd mount a larger diameter rod in my chuck, face it, and make a recess in it to hold my work piece.  Then I'd mount my piece in it and face it down to the desired thickness. (You can use a drop of super-glue if necessary to help hold the part.  If I remember right it will pop off easily if you heat it up a little with a propane torch).

I've seen web pages showing this technique, but of course I can't find a link when I want to Smile

Thank you for using this forum which I hope more people will do. But you might want to check out the 7×12 mini-lathe discussion group (even if you're not using a mini-lathe).  They're a much larger group and very helpful.

June 25, 2010
7:20 PM
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elizme
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I would like to know… What thickness of aluminum can I part from the end of a piece of solid rod stock and have the parted-off piece not be bent/broken/otherwise distorted? I imagine I can safely get down to 0.1″, but as I start to decrease the thickness of the parted-off piece, at what point will I run into trouble (assuming proper cutting speed, etc.)? Thanks so much for any help/advice you can give!

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