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Shop made carbide boring bar?

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  • Shop made carbide boring bar?

    I screwed up and managed to break a 1/4"x4" carbide end mill so now I have a 3 1/2" piece of carbide 1/4" in diameter. How could I convert this for use as a small boring bar? Other uses maybe?

  • #2
    like this maybe ...don't know how you are going to chop it up ..you may need a diamond disc

    maybe just score it and wack it and with a lot of luck it may break at the score like glass


    these are lathe boring bars i made to hold carbide bits ..but the idea can be applied to milling machine bars ..diagonals for blind holes ..strait for through holes





    all the best.markj
    Last edited by aboard_epsilon; 09-22-2011, 03:23 PM.

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    • #3
      A D nose reamer comes to mind.
      I never trust a fighting man who doesn't smoke or drink.
      William Halsey

      As a Machinist & Gunsmith I like to hear how to not can't do. P.A.R.

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      • #4
        Maybe braze a chunk on the end of it to make a boring bar? The nice thing about carbide is that it is stiffer than steel so you'll have a nice rigid shank.

        Maybe just try sharpening the end with diamond and using it at a slight angle? I haven't tried this myself.

        Also, you could just save it for dicing up into cutter bits as the guy above talked about.

        KEJR

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        • #5
          That would make a fine boring bar for small holes. You would chuck a pilot drill bit, mount a piece of steel in the toolpost, bring the carriage up to the drill bit and carry on with drilling a hole to mount the bar into. You would probably use pressure from the tailstock to push on the end of the steel holder-to-be while doing the drilling.

          The bar will be perfectly centered for height, and you would spend some time grinding a D on the end of the carbide bar. Grind away a little more than half the diameter so you can turn the bar in the holder to raise the cutting edge of the D back to center height. This gives you a little side rake angle.You would also grind a front relief angle and a side relief angle. Grind the side relief parallel to the bar, and back further than the depth of the D. You do NOT want to grind any more off the side than needed to bring the relief just up to the cutting edge. You don't get a front rake angle out of this, but you can cut with either the side or the front. You would need to drill a pilot hole in the workpiece first if you want to plunge cut.

          In use you would angle the bar slightly off-axis, with the side cutting edge a little towards the ID of the piece being bored. This means that the hole you're boring will have to be larger in diameter than the bar so the bar doesn't rub on the opposite side when it's in the hole any significant distance.

          I have a tool just like this, and I use it a lot. As always, don't hang out more length of the bar than you need to. It should be clear now as to what the holder needs to be like- I drilled and tapped for setcrews to hold the bar.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #6
            Well I spent a good deal of time last night grinding on that thing to achieve the "D" shape but sure enough it looks as if it will work just fine! Before I posted I was puzzled at how I could turn this thing into a boring bar for small holes by simply grinding but everything I had considered would have required angling the bar, after looking at the finished bar I had one of those "now why didn't I think of that" moments!



            KEJR, I have often wondered about brazing Carbide and just how difficult that might be. Any special procedures involved? Type of brazing alloy? I have been a welder by profession since 1968 so I understand the brazing process quite well it's just that I have never before had any reason to braze carbide.

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            • #7
              Originally posted by radkins
              Well I spent a good deal of time last night grinding on that thing to achieve the "D" shape but sure enough it looks as if it will work just fine! Before I posted I was puzzled at how I could turn this thing into a boring bar for small holes by simply grinding but everything I had considered would have required angling the bar, after looking at the finished bar I had one of those "now why didn't I think of that" moments!



              KEJR, I have often wondered about brazing Carbide and just how difficult that might be. Any special procedures involved? Type of brazing alloy? I have been a welder by profession since 1968 so I understand the brazing process quite well it's just that I have never before had any reason to braze carbide.
              Brazing carbide to steel is easy. You must clean the scale off from the carbide until it is shiny like steel. Then use SILVER SOLDER with flux. Heat until the silver solder melts. Done.

              Brian
              OPEN EYES, OPEN EARS, OPEN MIND

              THINK HARDER

              BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

              MY NAME IS BRIAN AND I AM A TOOLOHOLIC

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              • #8
                I don't know much about brazing other than that it can be done. Using silver solder like brian said seems reasonable. I'm going to have to just experiment with some scrap someday, but like anything you almost wait until you have need of a tool before practicing these techniques.

                So when you say D shape do you mean you cut through about half of the diameter to make a D shape? I've not tried it but I would think it would cut if you angled it to have rake and clearance. It might make a nice trepanning tool like that. I made one out of HSS for slicing a donut off a hunk of cast iron and I had to sharpen it alot even at proper speeds. HAving a carbide trepan tool for carbide would have been nicer.

                KEJR

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