Thursday, March 12, 2009

Through-holes Drilling

  1. Load the largest diameter bit to be used into the drill chuck, making sure that the depth ring is pressed firmly against the ends of the chuck jaws when they are fully tightened.
  2. Using a piece of scrap backing material as a gauge, adjust the spindle travel stop on your drill press to a depth that insures that the entire tip of the drill bit penetrates at least half of the material's thickness. You can also use two pieces of entry foil as a "feeler gauge" to set the depth. Under no circumstances allow a PCB drill bit to drill into the table of your drill press. PCB bits are specifically designed to drill copperclad and will shatter if plunged into cast iron, steel, or aluminum.
  3. Starting with the largest diameter drill bit, drill all of the through holes, stopping periodically to insure that the drill bit has not snapped off and that the spindle travel stop has not slipped.
  4. As you drill each hole size (from the largest to the smallest) check off that diameter on the drilling chart. This is a good bookkeeping technique that will help you keep track of your progress and insure that no hole size is missed.
  5. After all of the holes have been drilled, remove the backing material from the stack and reptape the remaining sheets with the dowel pins in place.
  6. Hold the stack up to the light for visual inspection. Ascertain that all of the holes have been drilled through and that none are blocked by drill debris. If some debris is seen, remove by carefully pushing a smaller diameter drill bit through the hole.
  7. If all of the holes in your circuit design go all the way through the board, you are now ready to activate the hole walls to prepare for through-hole plating.

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