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Boring bar...

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  • Boring bar...

    I want to reduce the inside of some pipe and I have a square tool holder that uses screws to hold the lathe tooling down. I use 1/2 lathe bits and want to set up a cheap boring bar without geting any expensive holders. Can a guy just take a round bar (wholesale tool) and grind a flat on 1 side to hold it or should I flat the top and bottom?

    I was concerned about how "Square" I need to be after I grind it by hand, is it hyper critical to get the point "exactly" a certain way.

    Or, does anyone make 1/2 square shank bars that dont cost a bunch? Or a round bar with flats already on it?

  • #2
    You could always do something like this:

    Location: North Central Texas


    • #3
      Hmmm, it seems that is "Exactly" what I need.... Sooooo...Do I have to make it of can I buy it somewhere?

      What size is that bars shank? I am trying to think what size I would need if I use 1/2 tooling, the thickness of that holder would raise the centerline of the cutter some?

      Keep in mind I am not a machinist, I just play with machines :-)

      [This message has been edited by Amity (edited 02-02-2005).]


      • #4

        You can buy those adapters, and the boring bars. They are not that expensive. They come in alot of sizes. 1/4, 3/8, 1/2, 3/4, and up.

        Look up busy bee machines, KBC tool, Travers tools, Grizzly machines, and there are others depending on your location.

        AS for the angle, yeah it is important. I am not an expert on this, so i will not attempt to give you the wrong advice.



        • #5
          I have two boring bar holders I bought off ebay on my lathe. Got them cheap.

          A old armstrong tool post. Both are too large for the boring bars I have thou, I have 1" and 1 1/4" holders and 3/4" bars. On a happy note, the boring bars chuck right into the toolpost holder. The flat spot tightens down on top. I have bought two dozen nice american made boring bars for less than $20 off ebay also.



          • #6
            If your armstong post is too big just bush it down with a split bushing made of crs.



            • #7
              In boring, bigger is always better -- less chatter, better finish, able to bore deeper, etc.

              I had same problem as yours...needed to do the job, not much $$$.

              Bought a 3/4" boring bar, new from J&L Industrial, about $30 (you can also find similar on eBay for $5-$10). Now for a holder...

              Took a 2" x 2" x 6" solid scrap (probably HRS). Drilled a 3/4" hole near one end for the bar, and put two set screws (one above, one below) to coax the tool point up or down. Drilled a hole through the 2x2 to mount to my compound.

              Worked so well that I bought a 1 3/4" boring bar from Penn Tool (about $90 new, hard to find on eBay) for bigger jobs.

              Cutting point height is pretty critical...need to be 0.010" above center, so take the time to get that just right and it will make you smile.

              Barry Milton
              Barry Milton


              • #8
                I have never noticed this type of holder in any of my catalogs and this one was awfully easy to make. The holder pictured is about 2â€‌ long, 1 1/4â€‌ wide, .800 high, and holds 1/2â€‌ boring bars. It does end up a little above center in my turret post, but I just pitched the cutting edge down a touch to get it where it needed to be IIRC. I now use a quick change TP so this isn’t an issue at all. Get one if you can, you WILL like it. If you want a quick solution, you can also get by with what jcurrell suggests in your turret tool post.
                Location: North Central Texas


                • #9
                  I have a set of 1" boring bars I started at work out of 4140 35RC shafting steel. These will be for HSS tool bit in the 1/4, 5/16 and 3/8 sizes. The cross holes where broached square one end and the other will be set up with a slot 60 degrees from the centerline so as to allow the bars to be used for ID threading. All the bars have flats milled on them the whole length at 90D intervals. I'd shot a couple of pictures but I am on a Family Leave right now for a couple of weeks
                  Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


                  • #10
                    Thanks for the tips gang. I needed to thin down the inside of a pipe today so I put some shim under my tool holder and used a piece of lathe tooling. It worked out fairly well,I must have gotten lucky on the height. I am going to dig thru the Wholesale tool book and see what I can make work in my 1/2 square holder.

                    I think I could make the holder in that pic, just not as purty.


                    • #11
                      The holder in the pic is very nice. Another way is to take a scrap piece of round or square stock that can fit in your toolholder, clamp it in place, chuck a 3/8" drill bit in the 3-jaw, and drill lengthwise through the round stock -- the hole doesn't need to be centered precisely. Use a hacksaw or mill to slit the far side of the round stock. Put your 3/8" shank boring bar in this and clamp it down in the toolholder. Since the hole was drilled in situ, the tool height should already be correct and not require shimming.


                      • #12
                        Awsome Idea, thanks man!