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hole drilling question

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  • hole drilling question

    A few weeks back I posted a question about increasing the throat of a drill press, I haven't had time to work on that yet, but now I need to drill a few accurately alligned holes in the middle of a plywood sandwitch 2.25 thick.

    The holes are 1/8", need to be as exactly vericle as possible, and will be located by drilling through a hole already in the pattern I'm mounting on the board. You guessed it, I'm aligning patterns on the cope & drag of a pattern board. I'm using pins through the holes to get registration.

    Any ideas on how to drill these holes vertically?


  • #2
    Drill bushings

    I would press a drill bushing into a 3/4 piece of wood and then use this to drill your holes. You can get drill bushings all over the place and the results are excellent.


    • #3
      Originally posted by neonman

      Any ideas on how to drill these holes vertically?

      watch for old school surplus auctions and get one of these.

      i have to admit, mine is in much nicer condition, and cost much less.

      andy b.
      The danger is not that computers will come to think like men - but that men will come to think like computers. - some guy on another forum not dedicated to machining


      • #4

        If I understand the problem you're considering, you're concerned about squareness of your pieces to the spindle centerline? That is, you have your pattern holes for location, but you want to make sure the hole in the plywood below your pattern is vertical?

        Unless I'm missing something, you only need to sweep your drillpress table with an indicator in the chuck to make sure the table isn't sloped in any direction.

        However, if straightness is the goal, you also face the possible problem of non-uniformity in the plywood which might bias a drill point so it wanders one direction or another. You can't control the plywood, but I think you'd want to make sure you're using a high speed on the spindle and a slower than normal feedrate for drilling. What you're hoping then is that the drill is stiff and the corners will act a little more like a mill cutter and bore in straight. In fact, if it's feasible you might consider using a square end endmill for drilling as far as you can reach.

        This is similar to the tooling problem of drilling holes on size and on position. An ordinary reamer will establish size, but the 45 degree corners will make it follow the hole if the drill has wandered, thus compromising positioning. The common practice for really accurate holes is to drill undersize to get most of the material out, use an offset boring head with a single point tool to establish a position in line with the spindle, then ream the hole for the slip or press fit required.
        "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill


        • #5
          If your just going through plywood I would use a plunge router, and if you are indexing through another hole use a guide collar to center everything.


          • #6
            WIth another person watching and giving guidance you can drill a pretty damn straight verticle hole with a cordless hand drill. KISS


            • #7
              Turn something in the lathe, face one end, then spot and drill a concentric hole through it. Walla, drill bit guide. Then use a cordless, and if possible, a drill bit with mostly shank and less flute. Withdraw often enough to clear chips.

              A long bit might be better, as that gives more depth to the hole, and more shank to be aligned by the guide.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-