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  • Small boring bar holding

    Which would be better for holding small solid carbide boring bars (0.125" shanks and up), an ER collet chuck or a solid holder? Both would be held by an AXA boring bar holder (0.750" ID)?
    Den

  • #2
    Actually, you need neither of the above. Get yourself a model AXA-2 turning, boring, and facing holder. They are exactly like the AXA-1 turning and facing holders, except that they have a "V" groove on the bottom of them. You set your boring bar into this "V" groove, tighten up the set screws, and go to work. If you're bar does not have a flat on the top, you have to eyeball it to get lined up correctly. But that's very simple, and this method works extremely well. Don't forget to set your center height while you're at it.

    Ed

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    • #3
      Ed: I hadn't thought about that as my concern was giving the tiny bars good support. I'll have to scope it out and see where they lie. Overall length on these little buggers is 1.5" so shank length is generally just a little bit over 1".

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      • #4
        I also use the "V" groove holders, even for the small bars, though an ER holder is my preference on CNC lathes.

        Most "V" holders - Aloris type, have about a 3/32 deep V, so they will hold well. The problem I have had with using carbides, only once then I lernt, was not to overtighten the 1/8 bars (I use many of these). I have gone to using "split bushings" of 1/2" diameter, drilled and reamed to 1/8" (or 3/16 or 1/4 for my other bars) for the shanks, and sawed on one side to create the split. Protects the bar, dampens the chatter better, and holds very positive.
        CCBW, MAH

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        • #5
          Stick a block of steel in your tool holder,chuck a center drill in the lathe chuck,centerdrill the blank,then drill and ream to fit your boring tool,tap in a setscrew and your good to go,plus its dead nuts on center.You can use one blank for several sizes of bars too,just put a step block under the hieght ajustment screw on the tool holder and repeat the afore mentioned process,next time you need that size hole just remeber to use the step block.
          I just need one more tool,just one!

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          • #6
            In the past I've run into problems when the boring bar sits to low in the quick change, Aloris type, standard tool holders ( the stop nut for center height hit the tool holder while the tool was still below center). Especially when you want to change the tool holders during the job. To solve this problem I took a piece of square CRS, larger than the dia. of the boring bar shank,and half the length of the holder (to catch 2 set screws). Drilled and reamed for the shank of the boring bar then using a slitting saw and cut down the length of the block into the bore. When you tighten down on the toolholder set screws it clamps the boring bar shank in the block and brings the center height of the tool closer to the center of the tool holder. I've done this for a number of my boring bars and always held the boring bar very well.

            Note: Try to keep the split side close to the center of the set screws for more holding power.

            Hope this helps,
            Frank

            [This message has been edited by PolskiFran (edited 02-06-2004).]

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            • #7
              Den

              Always use the least amount of overhang you can get away with and the largest diameter bar that will fit in your hole.

              The best way to hold any boring bar is to clamp its full diameter such as with a bored out block that has a saw slit on one side to facilitate clamping. This is known to reduce chatter and sympathetic vibrations in the bar which adversely affect the cut.

              The second most effect method is a bored hole in which the bar is place and then a screw is tighened down onto the bar itself through the block.

              The least prefered method is clamped in a standard toolholder or v-groove as suggested, although the v-groove is marginally better.

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              • #8
                Thanks guys. I think I'll drill out .750" rod and use double setscrews on the bar ... unless I get daring and slit it like Thrud suggested. The v-groove is handy for other odd sized bars and I'll probably use it for them.
                Den

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