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Just Can't Make It Chip ..........!

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  • Just Can't Make It Chip ..........!

    This has to be one of the worst jobs I've done in quit a while, turning down the flange on the 5C adapter plate. I don't know what the alloy is but it either streams and bird nests or winds springs some being over 5 ft. long. I've tried a few different style inserts all with various combinations of feeds and speeds and get basically the same results. With a .025 or more DOC it get a beautiful finish, the stuff comes off hot and ragged and if it starts to wind around the chuck I have to stop. After a pass I've found that pulling the carriage out fast leaving a slight thread look to the flange seems to minimize the streaming as the interuptions sort of make a breaking point for the stream. I've also found the the insesrt I'm using CNMG 432 does the best job. I could cut a lot deeper but that creates a lot more heat. Perhaps if I had coolant it may keep the swarf cool and brittle enough to curl and break small chips but I don't have coolant. Any suggestions?????? Having to turn off 1.25" on the dia. at .025 DOC chews up the better part of the day.

    JL.................





  • #2
    It looks like you have the power to use a negative rake tool. Have you tried that?
    Free software for calculating bolt circles and similar: Click Here

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    • #3
      I've had the same problem - often. I'll be curious to see how others have solved it - or not.
      I found that a shot of shop air will often direct the curl away from chuck at the beginning of the cut and
      then using a wire L shaped hook to guide the curl to run in a safe direction.
      It doesn't always work, but it's better than allowing the curl to run willy nilly, wherever it wants.
      CNMG is a negative rake insert.
      I cut it twice, and it's still too short!
      Scott

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      • #4
        Increase the DOC to .100-.200", increase your feed to .0065 or higher, increase your SFM to 3-600 SFM. You may have to play with the numbers, depending on your machine size and HP.
        The pull back marks are from spring, and are quite normal. You should be able to get rid of them by repeating the cut without changing anything else.
        Harry

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        • #5
          I bet that's an EN19/4140 steel or something very similar.
          Same thing happens to me, cuts beautifully but *really* struggles to break a chip - you can have it coming off so dark blue it's almost black, and it's still long and stringy.
          The only way I can get it chip is using a particular DCMT tool that I have that is loaded with a Sandvik GC4225 insert, with a funny moulded chip-breaker, and using an aggressive feed rate.
          Using different speeds or DOC seemed to make no difference, but for me this insert works better than any other I've tried, although there may be far better solutions.

          Picture here, although this is a CNMG rather than the DCMT I use.

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          • #6
            I think I have some square inserts??? SNMG I think, I could give it a try. I could cut much deeper but I don't want to take the chance of the 5C slipping in the hex block.

            JL................

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            • #7
              If its any help - or not - I had quite a job drilling my similar ER-32 adaptor. The drill had to be dead sharp, slow and forced fed with cutting oil to keep a constant chip with no rubbing. It work-hardened in an instant once the drill blunted and rubbed. It was almost impossible to drill out - so I changed the hole pattern slightly - was OK.

              There was no warning.

              With the job you are doing its more likely that you will get work-hardening once the feed stops and it rubs a bit before retracting the tool - TC will rub more drastically then HSS due to its cutting action.

              You may have to go back to "square one" - or perhaps make a new adaptor from scratch.

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              • #8
                Clamp a bit of steel on top of the insert, play about with position and angles .
                You want the chips to hit the packing and be forced to break up.

                Years ago you used to grind chip breaking grooves into tools. Problem with the carbide inserts is the chip breakers are designed for 2" depth of cut and 10,000 revs
                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                • #9
                  I would just about bet that the job is work-hardening during the cut and that flood cooling is inadequate as it needs to be jetted up to the point of cutting - which can make one big mess.

                  Work-hardening can start at the begining of the cut as the TC insert tries to force its way into the job and raise a chip as it may well rub at that point as well.

                  Just hope that the R8 and other finished surfaces have not distorted.

                  In the"early days" before TC became common it was quite normal to use "Stellite" tools as they took a lot of load and rubbing and heat and could be ground as you would for HSS.

                  http://www.google.com.au/#hl=en&suge...w=1920&bih=846

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                  • #10
                    Hi
                    Not sure how many you have to make and if this is in your budget, but I found the
                    Fix-Perfect from Kennametal the best turning insert for most work.
                    (It's a turning tool only..i.e. can not face).
                    I use it in a 7.5 hp Colchester 15 x 50. No problem taking anywhere from 0.010" to 0.200" cuts in
                    stainless to stressproof. Excellent chip curling....the best I have used...tried lots over the years.
                    Tool holder (5/8'' square shank) runs ~140.00 each....inserts from $ 30.00 each (come in a box of ten)
                    See link:
                    http://www.kennametal.com/kennametal...782/43292.html

                    Just a happy camper
                    eddie
                    please visit my webpage:
                    http://motorworks88.webs.com/

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                    • #11
                      I wish you did not have it but sorry to say, I like your problem...as a newb, sort of thing I wonder how to solve too/all the time. Awaiting more suggestions.
                      I found some materials (can't help much, "mystery metal") the DOC is the key and that sometimes there almost seems to be a very small range as far as feed rate goes, faster or slower than a fairly narrow window and the same things happen.

                      Re: chips...can I make a sort of wild/stupid stab...would there be any value (or way) to make a cut (saw, really small end mill) along the direction of travel...artificially create an interrupted cut?

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                      • #12
                        If it does not chip ADD more feed . Keep adding feed until it does.That is the trick.
                        Every Mans Work Is A Portrait of Him Self
                        http://sites.google.com/site/machinistsite/TWO-BUDDIES
                        http://s178.photobucket.com/user/lan...?sort=3&page=1

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                        • #13
                          Lots of good points and tips, etc. The insert is a Kennametal KC 730......... dead sharp, not a honed edge.
                          I don't think it's work hardening as I've drilled these with out a problem, it's just tough stuff. I'll see if I can come up with something to clamp down over the insert so the stream hits a wall and possible breaks. What would happen if these were being turned in a CNC enclosure. One couldn't have to keep stoping to weed it out.

                          JL....................

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                          • #14
                            Originally posted by JoeLee View Post
                            What would happen if these were being turned in a CNC enclosure. One couldn't have to keep stoping to weed it out.

                            JL....................
                            As Lane says high feed , bags of revs etc, remember they are using 25 HP spindle motors for a reason.
                            modern tooling is designed for this not us lot gnawing and chewing in a home shop
                            .

                            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                            • #15
                              I second what Lane said. Also up the speed until the chips are at least straw color. I really prefer them to be blue. I use an NS 730 ceramic from the Carbide Depot. If the KC 730 is a ceramic it works better as you turn it faster.
                              Byron Boucher
                              Burnet, TX

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