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How to avoid "singing" and work hardening

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  • How to avoid "singing" and work hardening

    I am trying to turn a piece of 3 inch pipe for a special project I am working on and I cannot for the life of me figure out (other than riding the back side of it with a rag) HOW to keep it from singing. I have Tried the full range of speeds this lathe (SB 9A) offered except the half speeds( back gear engaged) and at this point now have manged to work harden the hell out of it....

    Please Help me Fix this....

  • #2
    Got room to wrap a bungee cord around it?
    Len

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    • #3
      Singing is simply a higher frequency version of chattering. And that implies a less than ideal cutting arrangement. Speed and flexibility are the usual culprits. But a bad cutting edge geometry for the job you're trying to do can be a factor too.

      So, what cutting tool setup are you using? The fact that it's work hardening suggests that the cutting tip is rubbing as much as it's cutting.

      Another factor is the stickout of the material. Can you make up and use an end cap that can be supported by a live center at the tail stock?
      Chilliwack BC, Canada

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      • #4
        a pic of your setup might help these guys solve your problem.
        san jose, ca. usa

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        • #5
          What RPM are you using? 3" pipe is 3.5" OD, you should be 100RPM or below with HSS, that might be backgear territory. Pipe is not great material and doesn't turn well to start with. I've read of people stuffing rags/hose/other materials inside a tube/pipe and also setting up a stick of wood to ride on it and help dampen the harmonics.

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          • #6
            Some good advice already to quell the harmonics. Is a follow rest or steady rest an option for you as this would be a big help in stabilizing the work.

            Best option to avoid work hardening would be to take take more aggressive cuts. Once the tool bit has rubbed the work and applied pressure to the work without cutting you run the risk of work hardening if the piece you have is susceptible to this in the first place. Keep cutting, don't dwell. Once it's hardened it can be a a pain to machine.
            What are you using for tooling, HSS or carbide?
            Home, down in the valley behind the Red Angus
            Bad Decisions Make Good Stories​

            Location: British Columbia

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            • #7
              Is the end up the pipe supported? If not how much of the pipe is hanging out of the chuck? Do you have the cutting tool on center? If the material is black iron water pipe, I doubt that it's work hardening, the vibration might be destroying the cutting edge on your toolbit.

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              • #8
                I am using a 3/8s AL Carbide set at 90 (+/- a deg or 2) to the material I am turning and feeding Towards the Chuck. I do not at this time have access to 3/8 HSS I do have a box of uncut 5/16 HSS but am still working on the shims for my tool post(See Below) as they sit too low for the centerline. It Appears Spindle speed was a MAJOR issue as I was running at higher speeds and slow feeds....

                My tool post is similar in design to this.... Obviously I desire to switch to an adjustable height quick change... Just not in the budget right now....

                I have a couple of different 6" bench grinders here and I know wheels that work on mild steel WILL NOT Work on carbide... Where can I get 1 that is Inexpensive that will?? I suspect the carbides I have may not be the sharpest....EBAY....DO'H

                I may also be just a few thou high on my center line but if so we are talking a human hair or 2 it's that close... but I do not believe I am....

                I also DO NOT have a Follow or a Steady... On my list of things to Acquire...

                EDIT: Another note... the Pipe is 3 inch hot roll with a weld bead. Setup on an Inside clamp roughly 12 inches long.
                Last edited by FordFanatic1988; 07-20-2018, 03:19 PM.

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                • #9
                  Originally posted by FordFanatic1988 View Post
                  ...but am still working on the shims for my tool post... It Appears Spindle speed was a MAJOR issue as I was running at higher speeds and slow feeds....
                  Shims can be anything... an old set of feeler gauges work well.

                  As for chatter, of which I have much experience, I've found the usual solution is to get way more aggressive on the cut. If it's going to flex then let if flex and keep it flexed until the cut is done. Flex is not nearly as bad a bounce (chatter or singing). Sometimes, it's easier to get that aggression by slowing down the speed. Other times, just spin the knobs faster.

                  If it's chattered, then your carbide is likely toast. That happens a lot. Just grind up your HSS on the wheels you've got, it's not that hard to do, stuff something under it to get it to about the right height, and have at it. You'll save yourself a lot of grief. Save your carbide for when you need it and when you know how to use it without busting it up. Otherwise, if you try to use expensive carbide then you'll be too tentative, which will just wreck it, which will make you more tentative, which is just going to cost you more money. Use HSS and you won't care, you'll push it hard, and you'll get the job done. Meanwhile, you'll learn just how hard you can push your equipment. When you know how hard you can push it, and when you know HSS isn't going to cut it (literally), then THAT'S when you use your carbide. Once you've figured that out then you can use carbide all the time, if you want to. But, choice is good... and learning with HSS is cheaper.

                  David...
                  http://fixerdave.blogspot.com/

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                  • #10
                    You are totally set-up for failure. 12" is way way way way too long to do unsupported.

                    Get a plug in the end of that, and do it between centers, or between it chucked at one end and with a center at the other. I would use the 4 jaw to get the pipe running centered at the chuck end.

                    You will probably need to cut a groove in the plug for the weld bead on the inside. Trying to remove the weld bead would be dead easy if you had a steady, but you do not, and the chuck is not gonna swallow enough of that 3" pipe.

                    The toolpost is fine.... probably less flexible than a QC tool post (other than multifix). Yes, I would switch to HSS immediately, as the piece is fine for HSS, and HSS can be made sharp as heck with what you have. You need sharp. odds are the carbide is dull, besides being flat-popped if (as it sounds) you have brazed carbide and you cannot take a deep enough cut with it
                    Last edited by J Tiers; 07-20-2018, 03:49 PM.
                    2730

                    Keep eye on ball.
                    Hashim Khan

                    Everything not impossible is compulsory

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                    • #11
                      Hot rolled shouldn't work harden. A dulled edge on your cutting tool bit will lead you to believe that it may have work hardened.
                      Will a file cut the hot rolled tube easily? if so a good edge on a HSS tool bit should be all you need.
                      Home, down in the valley behind the Red Angus
                      Bad Decisions Make Good Stories​

                      Location: British Columbia

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                      • #12
                        On the topic of toolpost shims, I grabbed a bunch of pieces of steel banding from the dumpster at work. Cut to suitable lengths with snips, they made great shims in small enough increments to get me as close as I needed to be, height wise. Also, FREE!

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                        • #13
                          If you use the same size toolbits, and keep the cutting edge at the top of the tool, which is not hard, then you can make a "master shim" which goes under the whole toolpost. Gets rid of wobbly stacks of shims.

                          With access to a mill, one can also make a block-type shim the right height for each type of tool you use. The toolpost I use is similar to yours, and has a slot for each size, set up to be on-center when the cutting edge is at the top of the tool.
                          2730

                          Keep eye on ball.
                          Hashim Khan

                          Everything not impossible is compulsory

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                          • #14
                            I don't know why everyone is worried about "Harmonics" it's the Fundamental that that is the problem. :-) I wonder how many know what a "Harmonic" is ??
                            ...lew...

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                            • #15
                              Originally posted by Lew Hartswick View Post
                              I don't know why everyone is worried about "Harmonics" it's the Fundamental that that is the problem. :-) I wonder how many know what a "Harmonic" is ??
                              ...lew...
                              I do!
                              There are no stupid questions. But there are lots of stupid answers. This is the internet.

                              Location: SF Bay Area

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