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Good 5/8" - 3/4" boring bar?

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  • Good 5/8" - 3/4" boring bar?

    I'm thinking of making a 5/8" - 3/4" or so boring bar for my AXA boring holder on my lathe. I've seen some online that have a round or square hole in a bar with a setscrew to hold some HSS stock. I just didn't want to spend $15 on some chinese steel bar. to find out the hole fit like crap or the threads in the set screw need to be helicoiled, etc.

    Anybody have a good design that clamps some HSS onto a bar, or are the toolbit/setscrew designs OK? I really like the carbid insert boring bars, but I don't want to get setup with carbide just yet (Home hobby shop with mostly HSS tools now...). Also, I have an old small lathe and hear that they are not as rigid for carbide inserts.

    Thanks!

    KEJR

  • #2
    You can produce the square hole with a broach, if you have access to one, or by nibbling out the corners of a round hole with a file or a smaller square tool bit. A much easier way to get square holes is to purchase a square hole sleeve from MSC, McMaster Carr, or others and silver solder it in. Then you can drill and tap for the set screw.

    I've also see boring bars with a slot in the end, deep enough to have the toolbit at the back and a clamp screw just outboard. In that design you'd also need to saw a hacksaw or bandsaw slot to allow the spring needed to clamp the toolbit. For a round toolbit, you'd drill the crosshole, drill and tap for the clamp screw, then hacksaw a slot through both of those holes and a bit further back to get the clamping action. If the slot and hole description isn't clear enough I should be able to find a drawing or sketch to clarify if you need it.
    .
    "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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    • #3
      Thanks TG,

      It sounds like the clamp method would be good since you can have the tool be nearly flush to the end of the holder bar. I had thought of something like this but didn't know if anyone had any luck with this method.

      KEJR

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      • #4
        All the years I worked as a job shop machinist we made our own boring bars. I have quite a few of them now. However, in the spring of this year I bought two Everede insert boring bars for a special job I do. I have not used any of my home made bars since then. I use the Everede's for everything I do now but I will probably still use the home made bars at some point.

        The insert bars are so much better and easier to use it I could not believe it and the inserts are not that expensive unless you have to buy special inserts for exotic metals as I did. I have special inserts and standard inserts.
        It's only ink and paper

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        • #5
          How many HSS ones do you want? I've got a plastic shoebox full of em. $2 each.

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          • #6
            Agree with Carld. Just be aware that there is a steep initial learning curve with carbide inserts, both in terms of getting the right one, and then how to use it properly.

            Check ebay.

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            • #7
              A boring bar using the positive rake CCMT insert will work on any size machine. You can also get inserts for them that are sharp and polished for getting really nice finishes on aluminum. I also use these inserts for finishing cuts on steel and they work as well as a sharp HSS tool for that (well, at least as well as I can grind a HSS tool.)

              The good news about these inserts is that they also work really well for turning on HSM lathes and you can start slow because one holder for this insert can both turn and face without changing its position on the tool holder. I really like this for quicky jobs. The industry standard turning/facing holder for this insert is the SCLCR type.

              Search "CCMT" on this forum and on the practical machinist forum and you'll see a lot of discussion on this insert and tooling.

              www.maritool.com has good quality CCMT boring tools and www.latheinserts.com sells CCMT turning "starter kits" for HSM use.

              Good luck-

              Paul T.
              www.power-t.com

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              • #8
                One thing to look out for here, while CCMT is a very common insert (read: easy, inexpensive), for boring bars it is actually very uncommon. Double check that you don't mistake a CPMT insert for a CCMT insert holder. The former is labelled SCLPR/L and the latter is labelled SCLCR/L.

                The reason for the difference is pretty obvious the first time you chuck up the bar in your lathe. More relief angle allows clearance for working smaller bores while keeping your tool properly aligned.

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                • #9
                  Right now JTS Machinery & Suuply Company of Mentor OH has a sale on a set of 4 boring bars (5/16", 3/8", 1/2" and 5/8") which all accept a CCGT (or CCMT) 21.5x size insert. I believe it's $159 for the set and includes one insert for each bar.

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                  • #10
                    Originally posted by Arthur.Marks
                    One thing to look out for here, while CCMT is a very common insert (read: easy, inexpensive), for boring bars it is actually very uncommon. Double check that you don't mistake a CPMT insert for a CCMT insert holder. The former is labelled SCLPR/L and the latter is labelled SCLCR/L.

                    The reason for the difference is pretty obvious the first time you chuck up the bar in your lathe. More relief angle allows clearance for working smaller bores while keeping your tool properly aligned.
                    Arthur, most of the boring bars I've seen, like the one in the link I referenced, use the CCMT insert, which is nice because you can share it with your lathe tooling.

                    The relief angle you describe is important, but it is implemented in the CCMT boring bars by angling the insert pocket relative to the flats on the bars, allowing you to use the more common CCMT insert with the bars while still getting the correct relief angle.

                    Paul T.
                    www.power-t.com

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                    • #11
                      I recommend you look up Mesa Tool. Great products at a reasonable price. They have some very nice boring bars (with flats).

                      http://www.mesatool.com/

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                      • #12
                        Paul, yes you are correct that CCMT can be found. It is far more prevalent in import or lower-cost tooling probably for the very reason you mention---no duplication of inserts to stock. The name brands, though, are very shy of them. For example, Kennametal, Circle, Hertel all are CPMT. Only SECO, it would seem, stock a CCMT. Ultra-Dex, of course, offers both because they are awesome

                        ...My comment was more of a "heads up" than a "one is better". I, like you, use a CCMT bar for the same reason: the inserts interchange with my turning toolhoders. As a bonus, I have carbide and HSS from Arthur R. Warner that can be used on the same tool Great for those finnicky boring jobs that require a low DOC.

                        As an addendum for the OP, I have the double angle boring tools that McMaster sells. They are made by APT and are sized correctly, broached correctly, nicely black oxide finished and work as they should. I would just get the 3/4" and be done with it.
                        Last edited by Arthur.Marks; 10-06-2010, 01:39 AM.

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                        • #13
                          Originally posted by Arthur.Marks
                          Paul, yes you are correct that CCMT can be found. It is far more prevalent in import or lower-cost tooling probably for the very reason you mention---no duplication of inserts to stock. The name brands, though, are very shy of them. For example, Kennametal, Circle, Hertel all are CPMT. Only SECO, it would seem, stock a CCMT. Ultra-Dex, of course, offers both because they are awesome

                          <snip>
                          FYI, there are FAR more CCMT/CCGT makers out there than that, and not just the cheap import stuff!

                          Kennametal owns Circle and Hertel, and they have a wide array of both CCMT and CPMT style inserts and boring bars. So does Valenite, Mitsubishi, Sandvik Coromant, Walter, Sumitomo, Iscar, and many more.

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                          • #14
                            (Ducking for cover) Where do you even buy Mitsubishi or Sumitomo or Sandvik? I picture that they're only selling to high-volume manufacturers through independent sales agents. The listing of Sandvik's products goes on for volumes and volumes. It simply confuses me to hell. I guess I never run across any of the ones you mention other than maybe Iscar. It is still my impression that the general consensus when looking at wholesalers' catalogs like MSC, Travers, Enco, McMaster, etc. is CPMC for boring bars FWIW.

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                            • #15
                              If using HSS as a toolbiit one doesn't need to have a "square" hole in the boring bar. Just drill a hole in the bar that is just slightly under the diagonal measurement of the HSS bit and then file four slight groves such that the toolbit slips in. Then add a setscrew at the end of the bar to hold it from moving.

                              Or... if the above is too much work then buy round HSS blanks from Enco, or others, and use those in the boring bar with a setscrew.

                              Tip: If using a round HSS tool bit, place a small piece of brass welding rod between the tool bit and the setscrew to prevent the tool bit from rotating.

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