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do boring bars need hardening?

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  • #16
    Originally posted by Evan
    Never will it make a difference that matters. By the time the deflection is to the point of reaching deformation you already have a crash. Before that point there is no difference at all.

    your still not getting it --- if the inner facing wall is a crash of say .075" and just enough to bend the unhardened bar then the one that is hardened will make it through till you hit the feed release...



    What is the "resilience" value of 1020 mild steel?
    1020 mild steel is far less resilient than heat treated 4130,

    are you looking for a number rating? don't - read the write ups about the qualities and properties...

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    • #17
      Ummm, carbide is tungsten plus stuff. Carbide is like super hardened tungsten.

      If this boring bar uses an insert, then yes, I would at least harden the insert pocket.

      The one comment from Evan I don't get is why the ultimate yield (strength) of a boring bar doesn't matter. Isn't a hardened bar able to survive a light crash or oopsie without bending?

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      • #18
        Originally posted by A.K. Boomer
        Resilience is the ability to bounce back after an "incident"
        What you are talking about is basically elasticity. This is a defined term in metallurgy and the values are known and measureable.
        Amount of experience is in direct proportion to the value of broken equipment.

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        • #19
          Originally posted by Evan
          What kind of carbide?

          Im not sure - just know they make large solid carbide boring bars - very expensive and supposed to be very ridged...

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          • #20
            It might survive a crash in better shape but that isn't the point. Boring bars aren't designed to survive crashes, they are designed to be as stiff as possible and still fit inside the work. Tooling is not usually designed with crashing in mind.
            Free software for calculating bolt circles and similar: Click Here

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            • #21
              Originally posted by beanbag

              The one comment from Evan I don't get is why the ultimate yield (strength) of a boring bar doesn't matter. Isn't a hardened bar able to survive a light crash or oopsie without bending?
              Yes - because in his own statement he even admits it can go beyond what the non-heat treated bar can -- this equates directly to higher yield STRENGTH,

              the bar is simply more stronger and more resilient for the exact same given size and material - the only difference is the hardening ...

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              • #22
                Im not sure - just know they make large solid carbide boring bars - very expensive and supposed to be very ridged...
                Carbide is an "alloy" (compound) of carbon and a metal. Tungsten carbide is just one of many carbides that are common in metal working. It's the tungsten that makes a tungsten carbide boring bar stiffer, not the carbon. There is also silicon carbide, iron carbide, calcium carbide, tantalum carbide and so on. They have very different properties.
                Free software for calculating bolt circles and similar: Click Here

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                • #23
                  Us ghetto machinists have mini-crashes, like simply setting the feed rate too high, too deep of a cut, accidentally bottoming out, etc. So my guess is that a boring bar that is "stronger" is more likely to survive.

                  I wouldn't know because I have never snapped or bent a bar.

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                  • #24
                    Originally posted by Evan
                    It might survive a crash in better shape but that isn't the point. Boring bars aren't designed to survive crashes, they are designed to be as stiff as possible and still fit inside the work. Tooling is not usually designed with crashing in mind.
                    Not crashes particularly (like ramming the tool in to the chuck), but most insert tools have a hardened and quite sharp seating piece under the insert that will cut most materials for a while before giving up. This gives the operator some seconds to react to a broken insert before ruining the whole tool.

                    Have ruined my share of boring bars and milling cutters with inserts that didn't have that extra protection (the seating piece) and it is always so nice to order a new 200 EUR holder...
                    Amount of experience is in direct proportion to the value of broken equipment.

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                    • #25
                      the bar is simply more stronger and more resilient for the exact same given size and material - the only difference is the hardening ...
                      Not below the point of permanent bending. In use, a boring bar should never even approach that point with even annealed metal.
                      Free software for calculating bolt circles and similar: Click Here

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                      • #26
                        Originally posted by Evan
                        It might survive a crash in better shape but that isn't the point. Boring bars aren't designed to survive crashes, they are designed to be as stiff as possible and still fit inside the work. Tooling is not usually designed with crashing in mind.

                        Boring bars are different that way Evan -- esp. in non-cnc production work where you hit the feed stop and then hand jog it up to your mark,

                        were not talking about an all out "crash" were just talking about not meeting your mark a couple of passes and then all the sudden you meet it ---- so instead of a .025" little wall you now have .075"

                        and it may only be .005" deep but it's enough to let you know... to me a good boring bar is designed to survive some fair abuse this way, at least for production work....

                        The point is - if it's better than its better...
                        Last edited by A.K. Boomer; 06-10-2012, 03:12 AM.

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                        • #27
                          This gives the operator some seconds to react to a broken insert before ruining the whole tool.
                          The primary advantage is to prevent deformation of the seating area from the very high cutting forces exerted by the insert on the seat. That isn't at all the same as deflection of the bar. It's a wear issue of the insert seat.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #28
                            to me a good boring bar is designed to survive some fair abuse this way, at least for production work...
                            Hardening is not done for that reason. See above.

                            The point is - if it's better than its better...
                            It isn't better.
                            Free software for calculating bolt circles and similar: Click Here

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                            • #29
                              Originally posted by Evan
                              Hardening is not done for that reason. See above.
                              wrong - hardening can be done for multitudes of reasons --- overall strength for the same size package is important along with insert wear along with the resistance against gouging from cutting material...




                              It isn't better.
                              Of course its better - I just gave you three reasons why...

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                              • #30
                                Originally posted by Evan
                                The primary advantage is to prevent deformation of the seating area from the very high cutting forces exerted by the insert on the seat. That isn't at all the same as deflection of the bar. It's a wear issue of the insert seat.

                                There's some bars that are heat treated just at the ends and i'll give you that - there's also bars that are heat treated their entire length and that's for overall strength everywhere...


                                Edit; His OP is asking if they need to be and the answer is NO,
                                I also would not recommend it at all if like stated earlier it deforms the bar and makes it crooked as then he may have trouble getting it into it's holder --- but if he's confident he can pull it off why not - if he's not then why not do just the end of it to protect the insert seat and also harden the threads for the insert screw - another big bonus for durability...
                                Last edited by A.K. Boomer; 06-10-2012, 03:52 AM.

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