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2 flutes, 4 flutes, 6 flutes a dollar...?.

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  • 2 flutes, 4 flutes, 6 flutes a dollar...?.

    Ok, as just a home hobbyist, I know that the coatings run in this order


    Where does Colbalt and Carbde fit in.

    Also, I'm going to do a series of 5/16 squared shouldered recessed
    holes for a screw head in the middle of a metal block out of mild
    steel. Which would be better for a plunge hole, 2, 3, 4, or 6 flute?
    I have a bunch of these to do, what would be the best finish listed

  • #2
    Use a combo drill/counterbore.


    • #3
      Order relative to what?

      Cobalt isn't a coating -- it's an alloying element that produces particular varieties of high speed steel (HSS).

      Carbide is something else again entirely.

      For drilling "mild steel," in a home shop, hardly any of that matters much. AZSORT has it right -- get a combined drill/counterbore of the right size for the screws you're installing and be done with it.

      Note that an end mill won't give you a square-bottomed hole, anyway. The end flutes of an end mill are typically angled "up" in the middle by 2 degrees. Get a counterbore.
      See, for instance, or
      Try to make a living, not a killing. -- Utah Phillips
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      There are lots of people who mistake their imagination for their memory. - Josh Billings
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      • #4
        Barry Milton


        • #5
          precisionworks, I like the drop shadow! Nice touch
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          Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

          It is true, there is nothing free about freedom, don't be so quick to give it away.


          • #6
            I realize that "Cobalt" in not a coating, I use nothing but "Cobalt" drill bits. Most of what I drill is hardened armory steel. I was just wondering what actually cut the smoothest, and lasted the longest between the coated, "Cobalt", and "Carbide".

            I can't use the pilot counterbore combo because the holes I'm drilling are for non-standard holes. The heads of the screws are about 2 times as large a diam. as standard. The slight bevel on the end mill is not a problem, as I'm also making the screws, so I cun cut a slight bevel on the bottom of the head.


            • #7
              Carbide will last much, much longer.

              Keep in mind which grade of carbide to use depends on what you're milling/drilling.

              If you're going to order new, take the Manufacturer's reccomendations seriously.


              This Old Shed
              EGO partum , proinde EGO sum


              • #8
                It is tool steel, or mild steel. here is a photo of what I'm doing....


                • #9
                  The easiest way to counterbore those is to purchase a counterbore with the correct OD and reduce the pilot to fit. If you don't have the equipment to do this, any machine shop can reduce to the diameter you specify.

                  Ray, thank you for the compliment, but that picture belongs to the Google Image File!
                  Barry Milton


                  • #10
                    You can always get an interchangable piloted counterbore.


                    • #11
                      I do not know how I missed them in both my Travers, and MSC Catologes.
                      Thanks again