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Do you have to use a special drill in orderto tap threads?

I am new to this so I am not totally sure what I am talking about. But I am supposed to be cutting internal threads in a rod that are 5/16 x 18 UNC. I know that I am supposed to drill a hole first and than use a tap to cut the threads. But is there a specific type of drill bit that you are supposed to use? I know that you have to use a specific size. But are there different kinds? The chart says to use a size F .2570 drill. So as long as the bit says F, I should be okay right? Or is there specific type to use? This may sound stupid, but I just want to know

3 Answers

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  • 8 years ago
    Favorite Answer

    F or 1/4" bit should be fine to tap 5/16'' threads. You can use a cordless drill, corded drill, drill press or hand tap to tap the threads.

    If you're new to it I would suggest the hand tap as it would be the safest, and cheapest. It is basically a handle that holds the tap.

    Get a tap, and a little bit of wax and you be good to go.

    Remember though, safety first.

    Source(s): years of fabrication experience
  • 8 years ago

    I'm glad you were able to interpret the need for a .2570 bit.

    Selecting the bit depends on the material you wish to drill into.

    Cutting threads into a rod (co-axially?) will depend on the

    rod's hardness and composition (wood?,brass?, mild steel?, tool steel?)

    You cannot use a drill bit to make a hole in another drill bit.

    At a minimum, you will need a bit rated HHS. Possibly HHSco

    or HHSti.

    Either identify the rod material, or bring it with you when

    purchasing the drill bit from a knowledgeable supplier.

  • Roger
    Lv 7
    8 years ago

    Use a good quality size F (0.2570) drill bit, make sure the hole is drilled perpendicular to the rod. Then run the tap through the drilled hole. Use machine oil on the tap

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