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Made some insert holders last night.

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  • Made some insert holders last night.

    Someone had given me a box of Kennametal triangular inserts. I can't read the part number on the box but they are negative rake inserts. I made these insert holders from 5/8" keystock last night. I angled the insert down at five degrees.I tried one out on some mild steel they seem to work quite well.
    Can a good finish be achieved with this type of insert?

    Terry




  • #2
    yes good finishs can be achived with those inserts and metals given the CORRECT SFM (really fast usally.. like 300+) and cutting depth and feed and a good day. Till the insert gets a microscopic chip anyway.

    HSS is usally easyer to get good finishs with for hobbiests.

    Small warning: Any 'slack' around the insert can allow it to suddenly rotate a few tenths of a degree and start cutting at a diffrent depth/position.. though iv only experianced this myself when doing facing cuts and the insert passes the center point of the work.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      If the insert has a tapered screw hole, perhaps you should use a screw with a taper as well.

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      • #4
        Or put a taper on your screws. Iv seen that done before in a lathe.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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        • #5
          Unless you make them hard they wont hog off anything, the inserts will push metal and twist them up.

          They will work fine for light fast aluminum cuts and and plastic work. They wont hold up to turning steel like a real tool will.

          If you want the project to go farther then learn to case harden them then they will perform better anyway. thats a cheap way to make them better.

          good luck, harden them up and you have some good tooling.

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          • #6
            Are you guys kidding ?

            I've been making my own insert holders for years and they Hog metal just fine - 303 stainless, Inconel as well as Al. Never had any of the problems you guys are decribing. I do how ever harden the metal and then run it through the surface grinder. I couldn't imagine trying to get an HSS bit to hold up under those conditions



            Pictured above is Prehardened Stainless Steel being turned down on a Shop made tool holder with a A2000 grade insert
            Last edited by JoeFin; 10-25-2009, 11:09 PM.

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            • #7
              I do these commercially and the difference between home made and commercial is very slight.



              These are full pocketed ones, i.e. supported on two sides.
              Where they differ is they are milled in this case with a 10 degree tapered cutter to match the insert.
              The pocket is slightly less than the insert depth so the unused edges don't get rubbed on the tool.
              There is also a relief pocket in the corner, again to protect unused tips.

              These have a bridge and clamp fixing but if using a central screw drill and tap the hole very slightly off centre and towards the back edge.

              This has the effect of pulling the inset back onto the edge when tightening instead of locating around the screw which may give a bit of slack.

              J&L sell tapered cutters in different angles off the shelf.

              These then go for case hardening to 25 thou and hot blacked.

              No reason at all to make your own holders but make sure you either buy 3 or 4 packs of tips or that they can be obtained cheaply before you start, nothing like investing time into a holder that's too expensive to feed

              These tools go out on hired boring machines and when they come back they are always missing, they are charged for as consumables but the hire company got fed up of spending £55 to £65 per hire on a small piece of what is basically square steel.

              .
              .

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



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              • #8
                Originally posted by John Stevenson
                but if using a central screw drill and tap the hole very slightly off centre and towards the back edge.

                This has the effect of pulling the inset back onto the edge when tightening instead of locating around the screw which may give a bit of slack.


                .
                Nice work on the toolholders, and thanks for the tips.
                If you make the hole slightly offset, doesn't that stress the insert?

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                • #9
                  awsome looking holders.
                  I thought the flexability of steels was more or less the same?
                  Should'nt the only way a mild steel holder fail is possabley the insert denting the insert holding area itself?
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                  • #10
                    Originally posted by Black_Moons
                    I thought the flexability of steels was more or less the same?
                    That's right -- the modulus of elasticity (the rigidity) of all steels is nearly identical, and heat treating makes virtually no difference in rigidity.

                    But it's nice to case-harden toolholders to minimize the set screw bites...
                    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                    • #11
                      modulus of elasticity is the same, meaning that the materials have the same "spring constant". But as you harden, the yield strength goes up, meaning that it takes more force before the material takes a permanent set. However, brittleness goes up also, meaning that the chance of catastrophic failure increases also.

                      So to summarize, the difference between a hardened vs non-hardened toolholder:

                      small forces: they behave the same
                      medium forces: The hardened toolholder springs back while the non hardened one takes a small set
                      large forces: non hardened one is bent and hardened one is snapped

                      case hardening is a good way to go

                      PS: I'm not a mechanical engineer, I just made all of this up right now

                      I've made tool holderes out of non hardened steel, and a crash will take out both the insert, as well as jack up the pocket of the holder. I'd like to try a hardened tool holder, in the hopes that a crash will only take out the insert.
                      Last edited by beanbag; 10-26-2009, 03:11 PM.

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                      • #12
                        John,
                        Those holders are very nice.

                        Could/would you sell them to us ?

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                        • #13
                          I think the issue with case hardening is nothing much to do with either bending OR breaking of the shank.

                          It would be about the insert pocket.

                          A soft metal pocket will be hammered until it isn't flat anymore, by interrupted cuts, variations in materiel, etc, etc, etc. Eventually, you may snap inserts because the support is bad, or get problems from the insert wobbling.

                          The insert pocket on a hardened holder will not be hammered out of shape, and so it will last better.
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #14
                            Originally posted by J Tiers
                            The insert pocket on a hardened holder will not be hammered out of shape, and so it will last better.
                            They can be replaced in 30 minutes. Probably not that big a deal if they're not hardened. None of mine are and they're doing fine. And when they're beat to death I'll saw the ends off and remake them. If I'm still around.

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                            • #15
                              Originally posted by dp
                              They can be replaced in 30 minutes. Probably not that big a deal if they're not hardened. None of mine are and they're doing fine. And when they're beat to death I'll saw the ends off and remake them. If I'm still around.
                              No quarrel with that (surprise...... ??). Just commenting that the original matter of hardening talked of case hardening.... which doesn't necessarily affect the bulk properties, just the surface.

                              It's the only thing I can think of that is legitimately different in an important way for case hardening. Surface is not as easily deformed

                              Don't forget..... YOU are away chasing hackers and goofy users (assuming you are in IT, as I think I recall) or are otherwise employed while most machinists are busy making chips, maybe 2 shifts, on larger machines than either of us has. That puts a tiny bit more wear and abuse on their stuff
                              1601

                              Keep eye on ball.
                              Hashim Khan

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