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Cobalt drill bits?

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  • Cobalt drill bits?

    Do many here use cobalt bits as their every day drill bit choice? I bought a USA made set and I've yet to use them because I have so many HSS bits. They weren't cheap so I wanted to "save" them. It's been a year and they've yet to be used one time. I'm thinking about shelving the hss bits I keep by the DP and just using the cobalt all the time. Any thoughts or drawbacks to using cobalt exclusively?

  • #2
    I can't think of any drawbacks other than the cost. I have enough HSS bits to last a lifetime, but I always end up using the cobalt just because they make life so much easier. Either HSS or cobalt can be re-sharpened. Like you , a few yrs ago I decided to use all USA made bits from now on, and I bought all the fraction, letter, and number sets from Viking and Norseman. Absolutely no problems at all yet even in the hand drill. Only drawback like I said they are not cheap.

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    • #3
      Cobalt are slightly more brittle than HSS, but other than that are very good, just don't try drilling steel that is too hard, or you will burn the ends off. Having a few solid carbide drills in reserve used carefully will drill hard steel including case hardened.

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      • #4
        Originally posted by challenger View Post
        Do many here use cobalt bits as their every day drill bit choice? I bought a USA made set and I've yet to use them because I have so many HSS bits. They weren't cheap so I wanted to "save" them. It's been a year and they've yet to be used one time. I'm thinking about shelving the hss bits I keep by the DP and just using the cobalt all the time. Any thoughts or drawbacks to using cobalt exclusively?
        Depends on whether you sharpen them or not. I'd absolutely use the best drill I have (sans carbide) so I don't have to sharpen them as often.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

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        • #5
          Ditto on the carbide. I have a couple I use for pilot holes for hard steels. Where you have to watch Cobalt is during break through. I've snapped a couple of my small M42s. I really didn't think I was pushing them very hard either. They were cutting good in spring steel.

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          • #6
            Technically "cobalt drills" are also HSS, just a bit different variety.

            +able to drill harder or tougher materials like spring steel or stainless
            +stay sharp longer
            -more brittle than plain vanilla HSS, not preferred choice on handheld drill or sloppy drill press.
            -web(core) is usually thicker, needs split-point sharpening that is slightly more complex/difficult to do
            -more expensive
            -(grinding dust is more toxic than plain vanilla HSS. Cobalt is the nasty stuff also in sintered tungsten carbide tooling)

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            • #7
              Originally posted by CCWKen View Post
              Ditto on the carbide. I have a couple I use for pilot holes for hard steels. Where you have to watch Cobalt is during break through. I've snapped a couple of my small M42s. I really didn't think I was pushing them very hard either. They were cutting good in spring steel.
              Trick for drilling harder materials with carbide or M42 is to use backing plate. Put a piece of sacrificial steel behind the workpiece and the drill won't hog during break trough.

              You can drill 1/4" holes with carbide and handheld cordless drill to hardened file that way.

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              • #8
                Originally posted by MattiJ View Post

                Trick for drilling harder materials with carbide or M42 is to use backing plate. Put a piece of sacrificial steel behind the workpiece and the drill won't hog during break trough.

                You can drill 1/4" holes with carbide and handheld cordless drill to hardened file that way.
                I have done this on broken hi-strength bolts in engine blocks, it works good. I would *love* to know what alloy Ford uses on their newer exhaust studs... I am so glad that I am not the mechanic at work. Loaned him my 1/4" carbide spotter drills because whatever Ford used all broke off flush with the cylinder heads.

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                • #9
                  "Trick for drilling harder materials with carbide or M42 is to use backing plate. Put a piece of sacrificial steel behind the workpiece and the drill won't hog during break trough."

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                  • #10
                    Well, crap. I wonder what happened to the rest of my post? I'll boil it down--Thanks for the tip!

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                    • #11
                      If it were me I would save your nice expensive drills for when you really need them to drill harder or tougher materials. Use the general purpose stuff to do non-critical day to day work.

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                      • #12
                        Originally posted by challenger View Post
                        Do many here use cobalt bits as their every day drill bit choice? I bought a USA made set and I've yet to use them because I have so many HSS bits. They weren't cheap so I wanted to "save" them. It's been a year and they've yet to be used one time. I'm thinking about shelving the hss bits I keep by the DP and just using the cobalt all the time. Any thoughts or drawbacks to using cobalt exclusively?
                        Cobalt drill bits definitely last longer than HSS. They'll stay sharp and last forever if they stay on the shelf! 😀 If you have them might as well use them.

                        I've found that for the few and far between times I've needed something better than HSS it's just not worth the expense of inventorying a separate set of drills. In a non production environment slowing down a bit, and stopping to resharpen a few times is not that big a chore. If I do come across something that the HSS won't handle then it's a judgment call as to what else will work better. These are one off situations. Usually it's carbide.

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                        • #13
                          The absolute best purchase I ever made in drill bits was a USA made set of colbalt bits, Snap-On no less. That was 30 years ago and I still use them all the time. Of course the smaller ones have been replaced as they broke but everyone above 1/4 is still there and working. Use them man use them! Every time I do I say 'man that was a great buy.'

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                          • #14
                            Amen. I've never regretted the purchase. I get enough "hard stuff" to justify it. Cobalt is absolutely the way to go with stainless and nickel alloys. Also exhaust manifold bolts.

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                            • #15
                              OK, cobalt, one more thing to fuss about. I have eight or ten sets of drill bits so I must have some cobalt ones in there, but I really don't know where. Is there any way to tell which are cobalt and which are not?
                              Paul A.
                              SE Texas

                              Make it fit.
                              You can't win and there IS a penalty for trying!

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