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Horizontal mill question???

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  • Horizontal mill question???

    Hey guys! I'm wondering why some horizontal mills have two overarm supports.
    The new mill we have a to work (a verticle/horizontal) has two supports and I've now noticed a few used machines on ebay have the same thing. I'm assuming it's extra support for large cutters???
    I have tools I don't even know I own...

  • #2
    That's what I figured it was for, but it seems a bad design since it forms a rectangle, which is only as rigid as it's corner joints and loads the sides "in bending". Triangulation would seem to be a better solution, which leads me to believe there must be something else to it...
    Master Floor Sweeper


    • #3

      As far as I know, it's to let you get a bearing surface on the milling arbour close to both sides of a milling cutter. If you only have one, you'd put it just outboard of the cutter. If you have to have the cutter close to the outboard end of the arbour, that leaves a length of unsupported arbour which can flex. It just gives more rigidity.

      Also nice to have is some form of bracket between the knee of the mill and the end of the overarm - this really ties everything together!

      All of the gear, no idea...


      • #4
        Ian B has it right, when using, form cutters such as gear or sprocket cutters, you want the arbor supports as close to the cutter for ridgid support without running into the work, on larger jobs, we made our own offset arbour supports that would clear the rotary table and be as close to the cutter to prevent flexing of the arbor.


        • #5
          Oops, I thought he was talking about the horizontal bars, not the vertical arbor support arms. Sorry...
          Master Floor Sweeper


          • #6
            Arbor support is the reason,those big cutters crate big loads you can see the arbor"jumping rope" on some cutters without the support.
            I just need one more tool,just one!


            • #7
              There are two different style arbors, style "A" and style "B". The "A" has a small pilot at the end that is a machined feature of the arbor. An "A" support usually goes at the end of those arbors on the machined surface. A "B" arbor uses a support with a larger bore, usually a larger diameter than the spacer bushings. The arbor has a special bushing that fits the bore of a "B" support. The bushing can be placed anywhere along the arbor. This allows you to place a support near the cutter for heavy cuts. In some cases where you have a gang of cutting tools, you might see a "B" support somewhere on the arbor and a "A" support at the end using an "A" arbor and a bushing for the "B" support. On my K&T horz mill I use both styles, but I like to use the "B" style and set it as close to the cutter as possible. When used with only the outboard support the "A" is mainly for light duty cutting.
              Last edited by Mark Hockett; 12-10-2006, 03:30 PM.
              Mark Hockett


              • #8
                Thanks guys!
                Darin...the "rope jumpin" explanation was good!
                I have the "A" type arbour and was wondering if it would flex as there is nothing to keep tension on the outboard end.
                I'm thinking i may have to make up an extra overamr support.
                Boring head in the mill, them somekind of weird contrapshun to use the table Y to feed the support into the cutter.
                More projects. (Do machine addictions help us live longer? We sure need that to get all this done)
                I have tools I don't even know I own...


                • #9
                  The support arms really do the job.....

                  They tie the forces straight into the knee, and avoid a lot of the bending forces that go back through the overarm, the column, the knee ways, the knee, and up to the table.

                  By tying the end of the knee to the overarm or the arbor support, you get rid of the bending, substituting tension in the column and support.

                  if you have crossed supports, you also get some along-the-table support as well. The pic below shows the arms, but that cutter really isn't justification for them. Some of the others I have used are.


                  Keep eye on ball.
                  Hashim Khan