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An observation on drilling

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  • Gordon Haag
    For the past couple days, I have been drilling hundreds of holes in some sprockets to lighten them. They are made of plain mild steel, about a quarter of an
    Message 1 of 4 , Jun 18, 2013
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      For the past couple days, I have been drilling hundreds of holes in
      some sprockets to lighten them. They are made of plain mild steel,
      about a quarter of an inch thick. The sprockets are 11.75" 40 pitch,
      72 tooth. I used DraftSight, a really good free 2D CAD program, to
      print out a set of points spaced on a 5/8" grid. I then taped the
      printout to the sprockets and marked each point with a centerpunch.
      Each point was then drilled to 3/32", then 1/4", then finally to 1/2".

      The drill press is a really small Harbor Freight type, I think it is
      1/4 or 1/3 HP. The slowest rpm is 760, which I used for all bits.

      Anyway, I used 3/32" bits because I had a bunch left over from a
      previous project. I ended up breaking them all. I switched to just
      drilling straight in with the 1/4" bit. Accuracy doesn't really matter
      in this application.

      Expanding the hole from 1/4" to 1/2" was right on the edge of what the
      drill press can do. It took all the power and would frequently bind.
      The motor would get very hot and I would have to stop every 20 holes
      or so to let it cool down. I found a 3/8" bit and used this in between
      the 1/4" and 1/2". This made it easier on the press, but the bit would
      still bind and the motor still heated.

      All of the bits mentioned til now were HSS, the 1/4" and 3/32" TIN coated.

      I picked up a plain carbon steel 1/2" bit, sharpened it, and tried to
      drill with no pilot hole, just a punch mark. Remembering what I had
      read here about the ratchet drill, I pressed really hard. The bit not
      only drilled, it took a much less power and was easier on the motor.
      It did take longer for the hole to be drilled, but the press managed
      it much better. The table did flex down a bit, but again, accuracy is
      not important.

      In the first case, the limiting factor of the speed of the 1/2" bit
      was the power and torque of the motor, which is not large enough to
      efficiently do the task. In the second case, the bit was held back by
      how fast the center of the bit could deform the metal without a pilot
      hole.

      I think this goes to show how things must be thought of differently
      when one is limited in resources but not in time. This is the opposite
      of what most of the metalworking world assumes.

      I will keep drilling with the 1/4" -> 3/8" -> 1/2" system because it
      is faster and easier on the press. If I were out in the bush
      somewhere, I would conserve my bits and find a way to brace the table
      from bending.

      This group has really been an inspiration to me! Thank you.

      Gordon Haag
    • Steve Wan
      Hi Gordon There s a way to reduce the speed and increase the torque. I upgraded the 1/3hp china-made press drill (smallest range). There re bigger drill press
      Message 2 of 4 , Jun 18, 2013
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        Hi Gordon

        There's a way to reduce the speed and increase the torque.
        I upgraded the 1/3hp china-made press drill (smallest range).

        There're bigger drill press with step down speed. But I refused to buy
        new ones but I decided to improve it by shifting the driver step
        pulley to the middle and made the smallest cup pulley at the motor.
        Now I used either the a belt for 3mm to 6mm at speed 800rpm or change
        to 2 belts at 250 rpm for 6mm drill and above.

        The torque is great with pilot drilling. I was so impressed by the
        result I got another 1/3hp press drill to keep as spares.

        Steve Wan



        On 6/19/13, Gordon Haag <mr.meker@...> wrote:
        > For the past couple days, I have been drilling hundreds of holes in
        > some sprockets to lighten them. They are made of plain mild steel,
        > about a quarter of an inch thick. The sprockets are 11.75" 40 pitch,
        > 72 tooth. I used DraftSight, a really good free 2D CAD program, to
        > print out a set of points spaced on a 5/8" grid. I then taped the
        > printout to the sprockets and marked each point with a centerpunch.
        > Each point was then drilled to 3/32", then 1/4", then finally to 1/2".
        >
        > The drill press is a really small Harbor Freight type, I think it is
        > 1/4 or 1/3 HP. The slowest rpm is 760, which I used for all bits.
        >
        > Anyway, I used 3/32" bits because I had a bunch left over from a
        > previous project. I ended up breaking them all. I switched to just
        > drilling straight in with the 1/4" bit. Accuracy doesn't really matter
        > in this application.
        >
        > Expanding the hole from 1/4" to 1/2" was right on the edge of what the
        > drill press can do. It took all the power and would frequently bind.
        > The motor would get very hot and I would have to stop every 20 holes
        > or so to let it cool down. I found a 3/8" bit and used this in between
        > the 1/4" and 1/2". This made it easier on the press, but the bit would
        > still bind and the motor still heated.
        >
        > All of the bits mentioned til now were HSS, the 1/4" and 3/32" TIN coated.
        >
        > I picked up a plain carbon steel 1/2" bit, sharpened it, and tried to
        > drill with no pilot hole, just a punch mark. Remembering what I had
        > read here about the ratchet drill, I pressed really hard. The bit not
        > only drilled, it took a much less power and was easier on the motor.
        > It did take longer for the hole to be drilled, but the press managed
        > it much better. The table did flex down a bit, but again, accuracy is
        > not important.
        >
        > In the first case, the limiting factor of the speed of the 1/2" bit
        > was the power and torque of the motor, which is not large enough to
        > efficiently do the task. In the second case, the bit was held back by
        > how fast the center of the bit could deform the metal without a pilot
        > hole.
        >
        > I think this goes to show how things must be thought of differently
        > when one is limited in resources but not in time. This is the opposite
        > of what most of the metalworking world assumes.
        >
        > I will keep drilling with the 1/4" -> 3/8" -> 1/2" system because it
        > is faster and easier on the press. If I were out in the bush
        > somewhere, I would conserve my bits and find a way to brace the table
        > from bending.
        >
        > This group has really been an inspiration to me! Thank you.
        >
        > Gordon Haag
        >
        >
        > ------------------------------------
        >
        > -------------
        > We have a sister site for files and pictures dedicated to concrete machine
        > framed machine tools. You will find a great deal of information about
        > concrete based machines and the inventor of the concrete frame lathe, Lucian
        > Ingraham Yeomans. Go to
        > http://groups.yahoo.com/group/Multimachine-Concrete-Machine-Tools/
        >
        > Also visit the Joseph V. Romig group for even more concrete tool
        > construction, shop notes, stories, and wisdom from the early 20th Century.
        > http://tech.groups.yahoo.com/group/romig_designs/
        > -------------Yahoo! Groups Links
        >
        >
        >
        >
      • Adam Simmons
        I pretty much have the same press for home use, the biggest downfall of it is that it doesn t go slow enough. It gets the job done, but destroys bits, and
        Message 3 of 4 , Jun 18, 2013
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          I pretty much have the same press for home use, the biggest downfall of it is that it doesn't go slow enough. It gets the job done, but destroys bits, and sometimes accuracy.

          Slower is better sometimes, especially when you have time to give to your project.


          On Tue, Jun 18, 2013 at 5:08 PM, Gordon Haag <mr.meker@...> wrote:
           

          For the past couple days, I have been drilling hundreds of holes in
          some sprockets to lighten them. They are made of plain mild steel,
          about a quarter of an inch thick. The sprockets are 11.75" 40 pitch,
          72 tooth. I used DraftSight, a really good free 2D CAD program, to
          print out a set of points spaced on a 5/8" grid. I then taped the
          printout to the sprockets and marked each point with a centerpunch.
          Each point was then drilled to 3/32", then 1/4", then finally to 1/2".

          The drill press is a really small Harbor Freight type, I think it is
          1/4 or 1/3 HP. The slowest rpm is 760, which I used for all bits.

          Anyway, I used 3/32" bits because I had a bunch left over from a
          previous project. I ended up breaking them all. I switched to just
          drilling straight in with the 1/4" bit. Accuracy doesn't really matter
          in this application.

          Expanding the hole from 1/4" to 1/2" was right on the edge of what the
          drill press can do. It took all the power and would frequently bind.
          The motor would get very hot and I would have to stop every 20 holes
          or so to let it cool down. I found a 3/8" bit and used this in between
          the 1/4" and 1/2". This made it easier on the press, but the bit would
          still bind and the motor still heated.

          All of the bits mentioned til now were HSS, the 1/4" and 3/32" TIN coated.

          I picked up a plain carbon steel 1/2" bit, sharpened it, and tried to
          drill with no pilot hole, just a punch mark. Remembering what I had
          read here about the ratchet drill, I pressed really hard. The bit not
          only drilled, it took a much less power and was easier on the motor.
          It did take longer for the hole to be drilled, but the press managed
          it much better. The table did flex down a bit, but again, accuracy is
          not important.

          In the first case, the limiting factor of the speed of the 1/2" bit
          was the power and torque of the motor, which is not large enough to
          efficiently do the task. In the second case, the bit was held back by
          how fast the center of the bit could deform the metal without a pilot
          hole.

          I think this goes to show how things must be thought of differently
          when one is limited in resources but not in time. This is the opposite
          of what most of the metalworking world assumes.

          I will keep drilling with the 1/4" -> 3/8" -> 1/2" system because it
          is faster and easier on the press. If I were out in the bush
          somewhere, I would conserve my bits and find a way to brace the table
          from bending.

          This group has really been an inspiration to me! Thank you.

          Gordon Haag


        • Steve Wan
          Hi Adams That s what I trying to address, the small press drill can be reworked to run at slower speed not necessary to buy bigger drill press. Steve Wan
          Message 4 of 4 , Jun 18, 2013
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            Hi Adams

            That's what I trying to address, the small press drill can be reworked
            to run at slower speed not necessary to buy bigger drill press.

            Steve Wan

            On 6/19/13, Adam Simmons <xyrthx@...> wrote:
            > I pretty much have the same press for home use, the biggest downfall of it
            > is that it doesn't go slow enough. It gets the job done, but destroys bits,
            > and sometimes accuracy.
            >
            > Slower is better sometimes, especially when you have time to give to your
            > project.
            >
            >
            > On Tue, Jun 18, 2013 at 5:08 PM, Gordon Haag <mr.meker@...> wrote:
            >
            >> **
            >>
            >>
            >> For the past couple days, I have been drilling hundreds of holes in
            >> some sprockets to lighten them. They are made of plain mild steel,
            >> about a quarter of an inch thick. The sprockets are 11.75" 40 pitch,
            >> 72 tooth. I used DraftSight, a really good free 2D CAD program, to
            >> print out a set of points spaced on a 5/8" grid. I then taped the
            >> printout to the sprockets and marked each point with a centerpunch.
            >> Each point was then drilled to 3/32", then 1/4", then finally to 1/2".
            >>
            >> The drill press is a really small Harbor Freight type, I think it is
            >> 1/4 or 1/3 HP. The slowest rpm is 760, which I used for all bits.
            >>
            >> Anyway, I used 3/32" bits because I had a bunch left over from a
            >> previous project. I ended up breaking them all. I switched to just
            >> drilling straight in with the 1/4" bit. Accuracy doesn't really matter
            >> in this application.
            >>
            >> Expanding the hole from 1/4" to 1/2" was right on the edge of what the
            >> drill press can do. It took all the power and would frequently bind.
            >> The motor would get very hot and I would have to stop every 20 holes
            >> or so to let it cool down. I found a 3/8" bit and used this in between
            >> the 1/4" and 1/2". This made it easier on the press, but the bit would
            >> still bind and the motor still heated.
            >>
            >> All of the bits mentioned til now were HSS, the 1/4" and 3/32" TIN
            >> coated.
            >>
            >> I picked up a plain carbon steel 1/2" bit, sharpened it, and tried to
            >> drill with no pilot hole, just a punch mark. Remembering what I had
            >> read here about the ratchet drill, I pressed really hard. The bit not
            >> only drilled, it took a much less power and was easier on the motor.
            >> It did take longer for the hole to be drilled, but the press managed
            >> it much better. The table did flex down a bit, but again, accuracy is
            >> not important.
            >>
            >> In the first case, the limiting factor of the speed of the 1/2" bit
            >> was the power and torque of the motor, which is not large enough to
            >> efficiently do the task. In the second case, the bit was held back by
            >> how fast the center of the bit could deform the metal without a pilot
            >> hole.
            >>
            >> I think this goes to show how things must be thought of differently
            >> when one is limited in resources but not in time. This is the opposite
            >> of what most of the metalworking world assumes.
            >>
            >> I will keep drilling with the 1/4" -> 3/8" -> 1/2" system because it
            >> is faster and easier on the press. If I were out in the bush
            >> somewhere, I would conserve my bits and find a way to brace the table
            >> from bending.
            >>
            >> This group has really been an inspiration to me! Thank you.
            >>
            >> Gordon Haag
            >>
            >>
            >
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