3/4 drill or hole saw?

Shop, Garage and Tools

  1. pishta

    pishta I know I'm right....

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    Im attempting to drill EFI bung holes in a cast iron or AL slant six intake. Im cutting them 45 degrees off the runner and I dont have a mill, only a bench drill press. Im thinking maybe the hole saw with a long pilot bit would reduce the chance of bouncing the bit off the runner when started, but I have had less than good results with hole saws and metal. I think the last hole saw I had was tweaked as the cut was not uniform, seemed to wobble on the mandrel, ended up just holding the piece and letting the hole saw move it side to side as it found its groove. Also would a bi-metal hole saw work on cast iron? Im leaning toward the hole saw but if anuyone has a better idea, Im game. Its going to be a 3/4 hole to epoxy (in iron) or weld (in AL) my AL EFI bungs. I have seem posts where the guys just drill a 3/4 hole and lean the drill over and let it cut down to 45 but that seems ghetto and I need these to be inline fairly accurately. Thanks.
     
  2. 1968FormulaS340

    1968FormulaS340 Well-Known Member

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    I think I would take it to a machine shop and say..... Put some holes in this.

    If I didn't have the budget for a machine shop, I would save until I did.
     
  3. memike

    memike Super Moderator Staff Member FABO Gold Member

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    Drill press.... Build a jig to hold it tight in the drill press that will hold it
    at the same degrees to do a small pilot hole in each runner, slow as she goes with lube and a good bit... at slow speed go to a little bit bigger then the first one and so on, I don't know But I would think building a jig to hold it as I drilled would be the hard part ,,,,,, yes a machine shop would be my choice
     
  4. sr71mopar

    sr71mopar currently moparless

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    I would be tempted to drill a pilot hole and finish with a die grinder.
     
  5. jos51700

    jos51700 Well-Known Member

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    If you're going to run a rail, you're wasting your time and money. Seriously, that is not going to be stupid expensive with a machine shop. I'd offer to have you send it to me, but your shipping on it...probably a near-wash.

    That manifold is easy to bolt to a table and indicate off of. It's a piece of cake, not like a V8 at all.
     
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    • pishta

      pishta I know I'm right....

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      Perhaps a machine shop could make quick work out of this. I do have a few that owe me a favor. Sounds good.
       
    • C130 Chief

      C130 Chief Mechanical Genius

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      For the cost of a new bimetal hole saw you can take it to a machine shop. An end mill in a Bridgeport mill is the proper tool.
       
    • 67Dart273

      67Dart273 Well-Known Member

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      I've cut some impressive holes in mild steel with a hole saw, I believe the largest was 1 1/2 through 1/2" thick. You use a VERY slow cutting speed and LOTS of oil.

      But hole saws are "sloppy." I doubt you could ever get any kind of real accuracy out of em, as they can "walk" in the pilot.
       
    • pishta

      pishta I know I'm right....

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      $10...really? Ill take that bet....Ill let you know. Ill take it to a machine shop. :)
       
    • 71beater

      71beater Well-Known Member

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      "For the cost of a new bimetal hole saw you can take it to a machine shop. An end mill in a Bridgeport mill is the proper tool. "


      He's right ya know... On both counts

      $10 worth of gas should get you to the machine shop...
      And the end mill on the Bridgeport will make clean work of it!


      Sorry, couldn't help myself on that one!
       
    • PA Dodger

      PA Dodger Well-Known Member

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      Just looking ahead, have you thought about how you will hold the bungs parallel to each other and even across the top so the injectors will sit correctly for the fuel rail? You dont want to find out they all point different ways after the epoxy dries. I'm guessing you have a jig that the bungs will mount to to keep them in line spaced correctly? Just asking because I don't think you would have maintained enough location accuracy with a hole saw or a bench drill press.
       
    • Wolfy2U

      Wolfy2U Army Aviation Retired!

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      Don't know if this will help any.

      Quote from http://www.slantsix.org/articles/dibiase_efi/efi-conversion.htm.

      I've been told that the Clifford manifold would be best for converting to fuel injection because it is supposed to have better flow characteristics and already has the injector bosses cast into it. However, this manifold must be used with headers and that's something I didn't want to do. It is my understanding that headers are not the best choice for a turbo setup, which is my ultimate goal. Based on this, and the cost, I chose the aluminum Offenhauser 4-BBL manifold. This manifold is still available from JC Whitney (www.jcwhitney.com) as P/N 73ZX7653A for $230 (wrong picture on web site), and Performance Automotive Warehouse (www.pawinc.com) as P/N 5720. Of course, the least expensive alternative is to use your stock cast iron manifold, or even the stock aluminum manifold. For my setup I had Rance Fuel Injection (www.rancefi.com) do the machine work and weld the injector bungs and fuel rail brackets on my Offenhouser manifold. The total cost for the machining, welding, and the fabrication of the fuel rail was $460. Rance is also an Accel and Offenhauser distributor.
       
    • pishta

      pishta I know I'm right....

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      PAW? Where have you been man? I got a total of $19 bucks in my EFI manifold, and that was for the 17/32 bung drill bit. So frugal is the word..and the alignment will be done by placing the injectors in 6 1.5" bungs made from a 2' scrap piece of 6061 AL 1/2 pipe with a 3/4 OD. The 17/32 bit opens the ID just enough to slip in the injector to the step .400 in the hole. Seats the EV-6 type injector (thin Bosch plastic body) perfectly almost to the hilt. Put a smooth chamfer on the edge and oil the Orings, they slip right in tight) in the rail and then placing the entire thing in the pre-drilled holes, then tacking the bungs as they sit, all aligned and level. Remove the injectors and finish bungs (weld or epoxy) finish grind the overhang in the runner and your done. Injector alignment is not critical as the O ring seal is a little forgiving, but I dont see that as an issue. Fuel rail will be undrilled stock. That drill makes the perfect injector socket.
       
    • mattmatthew

      mattmatthew ^_^

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      i'd use some quality USA made cobalt bits in conjunction with some cutting fluid. start small (~1/16) and work your way up to 1/4 (i think this is the size of the pilot bit in the hole saw) in increments of 1/16-1/8. switch to a 3/4 hole saw at this point (a quality 3/4 cobalt bit is buck$, and most won't fit in a standard 3/8 chuck - shank is 1/2).

      also go at the slowest speed possible when drilling. on a drill press ideally you want to get it as low as possible but i've drilled plate pretty cleanly with a press that goes down to about 300 rpm. even slower better but sometimes not always possible.

      all said, it might still be cheaper to just pay someone to do it. quality morse brand cobalt bits in the 1/16-1/4 size go for about $3-4 ea and a quality bi metal hole saw like lenox could easily run you about $15-20.
       
    • turbodart68

      turbodart68 Well-Known Member

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      Have an engine shop do it. Rapp Racing Engines in Huntington Beach can do it for you. I bet it would cost an hour worth of labor and I think he charges 60 an hour.
       
    • Mrpatel

      Mrpatel 512Dart

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      I have had luck with the "step" drills.
       
    • oldkimmer

      oldkimmer FABO Gold Member FABO Gold Member

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      ............or could u use a reamer?.................kim........
       
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