No announcement yet.

Hand Drilling Larger Holes.

  • Filter
  • Time
  • Show
Clear All
new posts

  • Hand Drilling Larger Holes.

    Need to enlarge some holes to 21/32" in a transmission housing which have to be drilled with a hand held electric drill or somthing similar, are reduction
    gearboxs available to fit a standard electric drill so as to reduce the speed
    to an acceptable level for this size drill bit. (1/2" is about the limit with the
    drill I have)
    Alternative suggestions would be welcome.
    Thank You.

  • #2
    I would rent a mag drill, and then make up some kind of steel base plate that clamps on your work, that the mag drill can attach to.

    Usually, around here, they rent for $25 a day or so, which, considering they are $1500 or so new, is pretty decent.
    They are the right speed, have plenty of torque, and you can use annular bits as instead of twist bits- which are much better for what you want. An annular bit acts more like an end mill or carbide hole saw, and does not need to be entirely cutting in the material- ie, interrupted cuts.

    Like these-


    • #3
      Is the housing going to be drilled in place?

      If it's a good 1/2" drill, it'll have enough oomph to spin a 21/32" bit in I assume an aluminum housing. You can get silver and deming bits, they go up to about 1", but have a 1/2" shaft so can be run in a 1/2" hand drill.

      Do the holes have to be opened up to 21/32" diameter, or just slotted to align? A carefully wielded 1/2" carbide burr in a die grinder can do wonders when it comes to making mounting holes line up You also don't have the nasty wrist wrenching torque of a hand drill that has a bit hang up :O


      • #4
        look for a cole drill or a similar setup yes its handcranked but wow what its possible to drill I think there may even been a thread in the arkieves


        • #5
          Thanks for your informative replies. I feel a Cole Drill would be the way to go
          but obtaining one here may be a problem, going by the archieves they would be a great tool to have in the workshop for this type of drilling.


          • #6
            [QUOTE=Paul H]Is the housing going to be drilled in place?

            I assume an aluminum housing.

            Do the holes have to be opened up to 21/32" diameter, or just slotted to align?:

            The housing has to be drilled in place. (Drawbar mounting bolt holes on a
            Massey Harris 744D, similar to the 44 in the US)
            Housing would be cast iron.
            Holes are being drilled out to be fitted with Helicoils.


            • #7
              If you don't own one, a good half-inch drill is worth owning and any one worth its salt maxes out at say 700 RPM or so. I have a decent 3/8" drill that is 0-2100 RPM and a cheap Black and Decker 1/2" from years ago that is 0-700 RPM. At that speed and with the internal gearing, a good one makes a lot of torque and you should be sure to use the side handle. I injured my wrist once without it when mine "grabbed".

              Paul Carpenter
              Mapleton, IL