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Deep hole drilling

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  • Deep hole drilling

    I need to drill a 1/4" hole in aluminum, the hole depth is nearly 4" and the exit cannot wander by more than 30 thou. in any direction. I do not know the alloy, but it machines nicely, (could well be 6061). I have a full size vertical mill. I was guessing that a parbolic flute drill, slow feed, and lots of pecking to clear chips might work. Do you all have any suggestions for keeping the holes straight?


  • #2
    I dont know why it would wander more than your tolerance, unless the drill has been resharpened improperly. I would suggest you use some sort of cutting oil or even wd-40 just to keep the aluminum from sticking to the drill.


    • #3
      I concur with Mochinist.

      I like to use those extension drills fromt the home center for deep holes. They have enough flute for peck drilling and the solid shank makes them stiff.

      Don't go too slow, use plenty of feed and oil (WD-40 is about the best non-exotic stuff there is for deep holes in aluminum,) and peck about one drill diameter deep at a time. I'd go about 1000 RPM in aluminum for a 1/4" drill.

      WD-40 is much cheaper if you buy it in the gallon can and and easier to apply with a laundery squirter. I use WD-40 for a lot fo things including as a general machine cleaner. A $13 gallon lasts me about a year. How maby $3 spray cans is that?


      • #4
        I concur with Forrest on the WD. It seems to work very well with aluminum, at least the alloys I have used.

        Gallons are definitely the way to go. They make a "WD-40" hand pump, spray bottle with an adjustable nozzle. Tight stream to mist. Great for applying it precisely while milling or drilling.

        Paul A.
        Paul A.

        Make it fit.
        You can't win and there is a penalty for trying!


        • #5
          WD-40 works good, but I mix it 50-50 with ATF, much better surface finish from milling and shapeing. Helps drilling too.