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  • Boring head boring bars

    Any recommendations for indexable boring bars for a 2" boring head? Minimum diameter holes will be .375" and 1.5" deep.

  • #2
    SCLCR10 bars, cut down and turned to 0.375". They're cheap as chips ($5 each or so) as are the inserts. I bought 3 or 4 of the 12mm ones and cut them to different lengths so I can always use the shortest bar for the cut. If you get an SCLCL bar you can also do the OD of bosses without worrying about your boring head unscrewing.

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    • #3
      The usual suspects, Kennametal, Sandvik, Iscar, Dorian and Thinbit, Etc.
      Choose what best fits the job.

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      • #4
        Just a note on the sclcr bars, they don’t do a flat bottom.

        I do use them in the boring head though. Like mentioned above just cut to length. I use the same bars in the lathe and also have a turning tool that takes the same insert.
        Last edited by oxford; 03-10-2021, 07:14 PM.

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        • #5
          why won't the SCLCR bars do a flat bottom - they can bore to the bottom of a hole on the lathe. Or did you mean that they'll leave a ridged bottom depending on the depth of cut? Is that why most indexable boring head bars use TPMT style inserts with zero lead?

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          • #6
            https://accusizetools.com/products/1...-set-2627-9104

            I use these. They work very good. Could turn down shanks if necessary I’m sure.

            I think sclcr and similar have the cutting edge above center don’t they? I chose the above because they’re on center and they have round shanks so you can rotate them to the proper angle without working against flat spot on sclcr bar. Of course I could be totally wrong also🤷‍♂️
            Last edited by Captain K; 03-10-2021, 09:26 PM.

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            • #7
              Originally posted by elf View Post
              Any recommendations for indexable boring bars for a 2" boring head? Minimum diameter holes will be .375" and 1.5" deep.
              What size hole in the boring head? LittleMachineShop has a few options. Maybe this one, with a bushing if it's the wrong shank diameter:
              https://littlemachineshop.com/produc...ProductID=5436

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              • #8
                Originally posted by mattthemuppet View Post
                why won't the SCLCR bars do a flat bottom - they can bore to the bottom of a hole on the lathe. Or did you mean that they'll leave a ridged bottom depending on the depth of cut?
                Yes they won’t leave a true flat bottom, DOC will determine how “jagged” the bottom of it looks. May or may not be a problem depending on what you are doing.

                You can overcome this using these bars on the lathe if need be by feeding back towards the center of the piece to clean up the ridges.

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                • #9
                  Originally posted by oxford View Post

                  Yes they won’t leave a true flat bottom, DOC will determine how “jagged” the bottom of it looks. May or may not be a problem depending on what you are doing.

                  You can overcome this using these bars on the lathe if need be by feeding back towards the center of the piece to clean up the ridges.
                  On a lathe with this style insert I normally stop the cut a few thousandths short of the finish depth with each pass. Before I make the last measuring cut on the bore I've got a pretty good idea what it will be reading on the cross slide dial. I make a finish pass for the bottom of the bore, facing from the id out to the expected finish diameter, and then do the measuring cut and finish bore diameter, staying a few thou off the bottom surface. Facing the bottom of the hole from the id out leaves a good finish. When trying to go from large diameter back to center to finish the bottom surface there's too much cutting edge in contact with the work resulting in possible tool chatter.

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                  • #10
                    One of things I need to do are bearing seats, so a flatter bottom would be good. I'm not sure the difference between a 91 degree face angle and a 95 degree face angle would matter.

                    The 2" boring head will hold 1/2" shank tools.

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                    • #11
                      Be sure to check the tool shank diameter for a 2" boring head, some are 1/2" and some are 12mm. An 8mm indexable would start in 3/8" hole, but would need a sleeve for the head. The 1/2" or 12mm shank bars would be easy to fit to the boring head, and are cheap, so you could have a choice of lengths cut.

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                      • #12
                        Originally posted by oxford View Post

                        Yes they won’t leave a true flat bottom, DOC will determine how “jagged” the bottom of it looks. May or may not be a problem depending on what you are doing.

                        You can overcome this using these bars on the lathe if need be by feeding back towards the center of the piece to clean up the ridges.
                        makes sense, thanks for the education. Though the easy option (ha!) would be to buy a boring and facing head

                        I have some small TCGT inserts, might have to make up some boring bars for the mill. One issue I've found with the 12mm bars is the size of hole you need to start the job, so having 8 and 10mm step down shanks would be useful.

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                        • #13
                          An option you have for small holes is to get some small inserts and silver solder them to a steel holder. That can be more compact than having screw on inserts.

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                          • #14
                            Originally posted by elf View Post
                            One of things I need to do are bearing seats, so a flatter bottom would be good. I'm not sure the difference between a 91 degree face angle and a 95 degree face angle would matter.

                            The 2" boring head will hold 1/2" shank tools.
                            4 degrees

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                            • #15
                              Originally posted by Bented View Post

                              4 degrees
                              Obviously. But does it matter? Only the inner edge of the outer ring will touch the seat.

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