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Re: [multimachine] An observation on drilling

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  • 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 1 of 4 , Jun 18, 2013
      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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