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What type of drill bit needed for Stainless Steel?

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  • What type of drill bit needed for Stainless Steel?

    The trailers I build have a lot of stainless parts that need 1/2" holes drilled in them for quick pins and locks.

    Most of what I'm drilling is 2.25" OD x 1/8" wall 304 tube. There are two 1" SS ramp pins that need to be drilled with 1/2" holes for locks.

    What type of bit should I use? I now HSS will fry quickly, do I need carbide or cobalt? any coating recomended? I've been taking the stuff to a machinist but it would be easier if I could just do it myself.
    Justin Starkey
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  • #2
    HSS will drill many a holes in SS, are you using a drill press or by hand

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    • #3
      I use cobalt and Tap Magic for 308, it's just like drilling mild steel.

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      • #4
        Scott is right.

        All I have are HSS and I drill a good amount of SS.

        Are you pilot drilling? That will always help.

        Also, with SS, your feed pressure needs to be more than that of regular steel while watching your drill speed. Get the right combo and it works great.

        - Paul
        The only stupid question is the one that never got asked.

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        • #5
          The trick is slow rpm, plenty of coolant & more feed pressure than you use with steel. HSS bits will work fine. 1/2" bit I would use about 150/200 rpm. 1/8 or 3/16 pilot hole also.
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          • #6
            as said, HSS will work fine with stainless. stainless work hardens rapidly (up to the point the hole cannot be finished) if the drill rubs without cutting


            to add to the advice already given...

            drill bit MUST be sharp and sharpened correctly!
            concentrate on making chips/swarf and the hole will follow- if you're not making chips the s/s is work hardening and the drill will be destroyed
            if the chips are blue, slow the drill and/or add coolant

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            • #7
              Actually when the chips are gold on stainless, you are running too fast, the rpm's for stainless is usually about 50% less than mild steel, the rpm's listed are a good range. Coolant, whether it is oil, water, or even air will help you if your rpm's get too fast, and be careful of the stainless chips, they are much nastier than mild steel, look at them real close and you will see little saw teeth, Hope this helps, Paul
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              • #8
                BTW, go to MSC.com, they have lots of good info on drill bits, a 135 degree split point will help with centering and not 'walking' of the bit compared to a 118 degree, if you can, buy screw machine length, as they are shorter and do not flex as much. Cobalt? well, you need more rpm's and pressure, or you will screw up the bit. Carbide? well you better have one very rigid setup or you will be shattering them pronto. Best Bet, buy a premium brand HSS bit, Cleveland,Latrobe,or Morse and these should work fine. Good Drilling, Paul
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