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  • Lathe drilling Question

    I am drilling a .868 thru hole in 1018 steel 1" thru. Currently i am center drilling, then pilot drilling with a 1/2, then using a 3mt 55/64th drill. I would like to speed this process up as much as possible. What are my options with a 1hp lathe? Is there any drill i can use that is self centering and runs true? Thanks for any feedback.

  • #2
    drilling in lathe

    I don't know how long your drill bits are but maybe try using a jobbers length
    drill bit. Screw machine drill bits are the same length I think. Since they have a shorter over all length they won't walk so much. Hope this helps

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    • #3
      You say your lathe has a 1 hp motor, it would also be helpful to specify what speeds are available and which speed you are trying to use?

      Dave

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      • #4
        Originally posted by becksmachine
        You say your lathe has a 1 hp motor, it would also be helpful to specify what speeds are available and which speed you are trying to use?

        Dave
        speeds range between i would like to do this between 300 and 600 rpm.

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        • #5
          After center drilling you should use a pilot drill of a diameter that equals the width of the chisel point of the finished size drill. If you want to eliminate the center drill you can bring the back end of a toolbit to touch the pilot drill as it touches the work and it wiill hold it on center as you start to drill. Then you can retract the "steady" as you drill through. Peter
          Last edited by Oldbrock; 12-24-2010, 04:22 PM.
          The difficult done right away. the impossible takes a little time.

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          • #6
            Id consider going even slower for the final drill if you have a decent backgear. You would be amazed how much metal a 3/4" drill can remove at 200rpm given enough tailstock pressure and torque... The chips tend to clear out nicely if you can get them to be one solid chip that snakes up the flutes, No peck drilling needed.

            of course, I have allready replaced my 2" long tailstock under clamp with one thats uh, 10" long... Mainly so it would stick out BEHIND the tailstock, incase I needed to add a second bolted clamp ontop of it (Camlock tailstock, but after I reduced the cam travel to 1/3rd what it was, and made the clamp 5x longer, it now HOLDS), Otherwise my tailstock would move out as much as the drillbit went in.

            Also when I made my tailstock clamp, I made the clamping surface with a 'poor milled finish' to help get more traction. (Gives little grooves for the oil to get outta the way)
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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            • #7
              Drill a through hole using a 3/16, or so, screw machine drill bit and then go through with the 55/64. You may want to try a 55/64" screw machine drill bit only, but I think you're going to have HP issues. No need for center drilling, just make sure the inital drill bit stabilizes, before really going to it. You will want about 100 SFM for both drills, and use coolant.
              Harry

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              • #8
                Use a spot drill, not a centre drill....in theory a well done split point might bypass the spotting stage but i doubt it. Like BM says, slow down for big drills.....I doubt 1hp has the umph for high rpms. As for drills running true, thats a function of how well they're ground

                you can get pretty quick at it, spot, pre drill maybe 1/4" at high speed, drop the speed load the big drill....there's not a minute's work there and you're onto the big drill
                .

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                • #9
                  Originally posted by beckley23
                  Drill a through hole using a 3/16, or so, screw machine drill bit and then go through with the 55/64. You may want to try a 55/64" screw machine drill bit only, but I think you're going to have HP issues. No need for center drilling, just make sure the inital drill bit stabilizes, before really going to it. You will want about 100 SFM for both drills, and use coolant.
                  Harry
                  excellent...thanks!

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                  • #10
                    If your holding that bit in a morse taper in the tailstock, don't be afraid to use a lathe dog to take the brunt of the torque. It will prevent the drill from spinning in the MT socket and galling either the drill taper, the socket or both. Just a reminder...
                    Location: Saskatoon, Saskatchewan, Canada

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                    • #11
                      One extra thing to bare in mind if you are pushing some big drill bits hard while using the tailstock.

                      Tailstocks are not really designed to transmit huge amounts of torque through the key that keeps the quill from turning.
                      With a 1 hp lathe I would think that the quill and key are not that heavy.

                      If your are going to take aggressive cuts you may want to consider using a dog to transmit the torque rather than letting the quill key take all the load.

                      Edit to add....Arcane is faster with his trigger finger than me!
                      Last edited by Willy; 12-24-2010, 04:54 PM.
                      Home, down in the valley behind the Red Angus
                      Bad Decisions Make Good Stories​

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                      • #12
                        Do you have access to a drill press or mill?
                        If it's just a simple drilling job, then drilling holes is ALOT easier and faster on a drill press or mill, then on a lathe.
                        I clamp my 3-jaw chuck on the mill table, find center, spot, and drill away.
                        Sure beats cranking away on the tailstock.

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                        • #13
                          Jump,

                          I have a similar project to do (I hope). I will be drilling a 7/8" hole through 1" of A36. I ran the problem through my Machinist Toolbox (software). It spit out:

                          Surface Speed:75FPM
                          Spindle Speed: 327RPM
                          Feedrate: .8829IPM

                          I believe the horsepower requirement is about .5HP

                          I plan to use a .875 MT3 (usa made HSS) drill and machine drive it with the carrage using a MT3 tool holder in my QCTP (tool holder has a slot for the tang). Will use flood cooling. (I have 50 to do)

                          My machine is 2HP. I plan to center drill it then do it in one shot at 7/8.

                          Comment


                          • #14
                            Originally posted by tmc_31
                            Jump,

                            I have a similar project to do (I hope). I will be drilling a 7/8" hole through 1" of A36. I ran the problem through my Machinist Toolbox (software). It spit out:

                            Surface Speed:75FPM
                            Spindle Speed: 327RPM
                            Feedrate: .8829IPM

                            I believe the horsepower requirement is about .5HP

                            I plan to use a .875 MT3 (usa made HSS) drill and machine drive it with the carrage using a MT3 tool holder in my QCTP (tool holder has a slot for the tang). Will use flood cooling. (I have 50 to do)

                            My machine is 2HP. I plan to center drill it then do it in one shot at 7/8.
                            Excellent idea! I may try that route also!

                            Comment


                            • #15
                              Let us know how it works out for you!!

                              In addition to drilling that hole, I am going to have to tap it to 1"-8tpi. Since I have so many to do, I thought I would give power tapping in the lathe a try. The lowest speed on my lathe is 70 RPM.

                              Good luck with your project,

                              Tim

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