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been practicing and got questions on tools and turn results

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  • been practicing and got questions on tools and turn results

    Hello all,

    So I ground my first tool.. a simple tool for turning right to left. I can take pics if wanted. well I'm turning some 6061 al, and it appears likes its tearing chunks out of it instead of a smooth nice looking cut (again can take pics if needed). I've tried turning at around 300 rpm up to 1100 rpm on my little 7x14 lathe. I used the autofeed as well as turning by hand to slow it down. Depth of cut was between .005 and .001".

    Any advice would be appreciated.

    Shaun

  • #2
    Is the tool bit on the centerline?

    Let's see the photos...

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    • #3
      To the best of my ability yes. Mike.

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      • #4
        Make sure the cutting edge, that you ground, is at dead center or a few thousandths below. Center being the axis of rotation of the aluminum stock that you are turning down

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        • #5
          If it's above it will chatter. If at or below it won't

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          • #6
            Pictures would be a definite plus.

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            • #7
              will get some pics. and will also try lowering it in the qcth. thanks for the help guys. it may be chatter but it doesn't look like any chatter i've ever seen before.. but i'm new to this stuff.. so????

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              • #8
                A good way to check tool height is to pinch a 6" steel rule between the tool tip and the work. Adjust height until the rule is vertical.

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                • #9
                  Slow it down? Your RPM figures are worthless without a diameter so that SFM can be calculated. Heck, you may need to speed it up.

                  Aluminum can be gummy and that can cause what you describe. It builds up on the cutting edge, effectively dulling it. The next two ideas are to fight this.

                  Use some cutting fluid. WD-40 works great for aluminum.

                  Is your tool dead sharp? If you just formed it on the bench grinder, try finishing it with a fine oil stone. For cutting aluminum, I like the tools to have a mirror finish. This can also be accomplished on a belt sander with a fine belt (perhaps even a worn one) and a bit of cutting oil added.

                  Do you have a proper clearance angle on your tool? If not, then you are plowing instead of cutting.
                  Paul A.
                  SE Texas

                  Make it fit.
                  You can't win and there IS a penalty for trying!

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                  • #10
                    You should be getting mostly continuous curly swarf that resembles a "slinky". I thought it was actually "invented" by a machinist when he saw how the swarf from lathe turnings acted. It looks like this:



                    Here is some swarf, but mostly from drilling, so it has a conical shape matching the cutting angle of the drill bit:



                    For turning, the cutting action is mostly on the left side of a right-hand lathe bit, and it should be perpendicular to the axis of the spindle, or slightly angled so the outer diameter is cut more than the inner diameter. I have found that a tool shapened to about 90 degrees and positioned so that the tip has a few degrees of relief behind the cutting edge makes a pretty good finish. It's also important to have a slight radius on the cutting point, and the cutting edges should be honed with a fine diamond file or stone until it is smooth.

                    Here is a video clip showing me turning an aluminum disc:
                    http://enginuitysystems.com/pix/engines/DSCN0855.AVI
                    Last edited by PStechPaul; 03-04-2015, 06:11 PM.
                    http://pauleschoen.com/pix/PM08_P76_P54.png
                    Paul , P S Technology, Inc. and MrTibbs
                    USA Maryland 21030

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                    • #11
                      ditto what everyone else said. In addition, at those depths of cut any flex or movement in your compound, cross slide, toolpost etc will push the work away and then you'll get it springing back for a deeper cut, then push away. Try a 0.01 or 0.02 cut at least and see how it cuts. If you're not getting a good cut, something else is going on.

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                      • #12
                        will try the level with a steel rule trick. Paul, sorry i did use the oatley cutting oil. will try wd40 as well. stock was originally .750 diameter and last cut was measured with a mic at .690. I do believe i have proper clearance angle and even tried playing with the angle tool approaches material to several different tries.. pics to follow

                        tool

                        material

                        angle of approach.. tried this to a straight 90°

                        i will do some more but i did do some honeing with my lansky fine and ultra fine stones.. again thanks for all the advice keep helping a newby guys

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                        • #13
                          You might be getting vibration in the stock. Depending on how far it sticks out the chuck, and also how far it sticks out on the left hand side of the headstock. Shorter stock is less prone to vibration, which can lead to chatter or a grainy, irregular surface.

                          Have you tried turning between centers ?
                          Gary


                          Appearance is Everything...

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                          • #14
                            Gary will put a center and see if it helps

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                            • #15
                              Your cutting tool shouldn't have a sharp tip like a dagger. It should have a very small radius, about .030" on the tip. This radius is best achieved by "wiping" the tip along an oilstone. The right hand side of the tool just adjacent to the tip should be just a small bit off parallel from the side of the workpiece. It is too aggressive the way you have it set up.---Brian
                              Brian Rupnow

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