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Screw vs Clamp Carbide Insert Styles

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  • Screw vs Clamp Carbide Insert Styles

    All of my carbide inserts for the lathe use the screw down type. It is a larger screw in the center of the insert. I've never had an issue with it, except for one time when the screw fractured while tightening.

    I'm about to buy more tools and have the option of getting the clamp down type with a pivoting lever. It seems this is more common on larger machines.

    The inserts and tool holders are about the same price. What do you guys use and why?

  • #2
    I have several of each type. I never paid much attention to how the insert was held. My main concern when I was buying them was the style / shape of the insert needed.

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

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    • #3
      Originally posted by JoeLee View Post
      ...I never paid much attention to how the insert was held. My main concern when I was buying them was the style / shape of the insert needed...
      I pretty much have the same thoughts. Either style works fine for any kind of work on any lathe. The single screw
      style (TCMT, TCGT, CCGT. SCGT, etc.) are usually a bit cheaper and do sometimes give you a little more clearance
      around the insert but other than that for the most part they are interchangeable...

      Keith
      __________________________
      Just one project too many--that's what finally got him...

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      • #4
        I was told that inserts can shift in clamp type tool holders unless they also have a locating pin.

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        • #5
          Originally posted by reggie_obe View Post
          I was told that inserts can shift in clamp type tool holders unless they also have a locating pin.
          Yes and no. Most are designed so the force against the tip of the insert drives it into the pocket. I'd have to take a closer look at some of the ones I have. I've never had a clamp type insert ever come loose or move.
          I'm I'm sure it's possible to have one move if you're back cutting with it. It could pull it out of the pocket if that's what you mean. The CNGP style are eccentrically pinned and clamped and are designed for heavier cutting.
          other styles like DNGP and VNGP have to be pinned just because of the size and style / shape of the insert.


          JL.....
          ​​​​​
          Last edited by JoeLee; 10-24-2021, 12:49 AM.

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          • #6
            Use what works for your application, if plowing off 1/8" DOC's at .015" IPR feed rates then a very robust clamping system is used.
            Sandvik and Kennametal make excellent tools most of which are clamp down.

            Internal tools are often screw down because the clamp increases the minimum hole diameter a good deal, above 2" diameters this is not a consideration.
            Last edited by Bented; 10-24-2021, 12:53 AM.

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            • #7
              Originally posted by reggie_obe View Post
              I was told that inserts can shift in clamp type tool holders unless they also have a locating pin.
              All of my clamp type toolholders have locating pins. You can buy them without pins but they're not as common.

              Keith
              __________________________
              Just one project too many--that's what finally got him...

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              • #8
                Originally posted by kuksul08 View Post
                All of my carbide inserts for the lathe use the screw down type. It is a larger screw in the center of the insert. I've never had an issue with it, except for one time when the screw fractured while tightening.

                I'm about to buy more tools and have the option of getting the clamp down type with a pivoting lever. It seems this is more common on larger machines.

                The inserts and tool holders are about the same price. What do you guys use and why?
                Clamp is more common on double-sided inserts(CNMG etc.) and screw is more versatile( better for smal boring bars.) Functionally they both perform ”good enough” for home shop so it comes down to cheaper cost per cutting edge vs versatility.

                If you have large 10hp lathe and lots of material to rough you should probably look for double-sided clamp mounted inserts that give you 4 to 8 cutting edges per insert.

                If you are looking for a versatile insert that works for light cuts(less than 5hp), fits to boring bars smaller than 1” and is widely available DCMT and CCMT are really common and goog choices.
                Location: Helsinki, Finland, Europe

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                • #9
                  The big names like Sandvik and Kennametal make their toolholders in all of the variations, and if one style turned out to be inferior, they wouldn't continue to make them. The type with just the pivoting lever are the fastest to change inserts.

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                  • #10
                    I much prefer the screw down type, although who has never lost a screw in the chip pan of their machine?

                    The clamp type don't give as much visibility of the insert pocket sometimes so you can't always easily verify there isn't a small chip that would cause the insert to not be accurately seated. The clamp type seldom have molded in chip breakers which means you might need a chip beaker insert on top of the cutting insert. Way too much hassle IMO.

                    Back in the day I recall seeing an older 8" 50 taper face milling cutter using negative rake clamp down inserts (prior to screw down type) where each insert had to be dialed in. There was some sort of adjustment to the holding pocket. All I can think is the inserts must not have been accurately ground to size from the factory so dialing in was needed. Changing inserts took at least half an hour, more often an hour.

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                    • #11
                      subscribed

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                      • #12
                        Originally posted by DR View Post
                        The clamp type seldom have molded in chip breakers which means you might need a chip beaker insert on top of the cutting insert. Way too much hassle IMO.
                        I'd say this was the situation maybe 20 or 30 years ago. Haven't seen (m)any "plain" inserts in commercial shops during this millenium.
                        just take a look on google picture search for any -NMG insert ie TNMG, WNMG and you have plenty of chip breakers.
                        OK, strictly speaking these are pin or pin+clamp mount inserts but..
                        Location: Helsinki, Finland, Europe

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                        • #13
                          I have had a few screw down only inserts move during a heavy cut.
                          No crash, just you loose your size setting.
                          On a small lathe for hobby work, screw on are just Ok.
                          But I would never buy them again. Shars has nice clamp down
                          holders for not too much investment.

                          -D
                          DZER

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                          • #14
                            Originally posted by Doozer View Post
                            I have had a few screw down only inserts move during a heavy cut.


                            -D
                            Was that a insert holder with proper "pocket" or one of those nasty looking triangular insert holders?
                            These look like they are destined to fail in heavy cut: https://www.shars.com/1-2-indexable-...rning-tool-set

                            Some earlier iterations even had normal allen head screw without the taper that pulls the insert in the pocket properly.
                            Location: Helsinki, Finland, Europe

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