Boring bar selection questions - Page 2
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  1. #21
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    Cut down the tool holders to put (2) in there opposite each other.

    Even if you want to take a single point finish cut (for no retrace lines)

    get a second tool in there opposite the first to take out most of the material
    in one cut, it will also help reduce deflection, being balanced.

    Set your bar on center, feed in for the roughing cut.
    Back out, dial in the finish cut (maybe .015) and use the bar with only the one side
    for the finish.

    Make provisions for the T-nut on the cross slide to handle (2) bolts/all thread
    (you'll have to swing the compound).

    If your taking the time to make a bar, you might need the extra hold down, and by having it already there, little time is wasted if you run into problems with vibrations.

  2. #22
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    Quote Originally Posted by digger doug View Post

    get a second tool in there opposite the first to take out most of the material
    in one cut, it will also help reduce deflection, being balanced.
    Thanks for the extra explanation, Doug. When you are talking about the "second tool in there opposite", do you mean upside down, cutting a 2nd cut on the "right" side of the pipe ID?

    What I'm not understanding, with that setup, is how to get the cutting tool centered on the "backside." It would be below center.....right? Is this ok? Otherwise, I'd have to make the slot twice the height of the toolholder to shim it.....am I thinking correctly?

    I appreciate the help.

  3. #23
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    Quote Originally Posted by hawkfan9 View Post

    What I'm not understanding, with that setup, is how to get the cutting tool centered on the "backside." It would be below center.....right? Is this ok? Otherwise, I'd have to make the slot twice the height of the toolholder to shim it.....am I thinking correctly?
    Either that, or cut the slot wide and mount your setscrews on opposite sides, or grind your tools so that the cutting edge is midway through it, or some combination of any of that, as long as the cutting edges are in line with each other and oriented opposite to each other.

  4. #24
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    I have bored 20 inches before with a 2in bar. Milled a perpendicular slot in the end of the bar 1/2 wide for a small shank turning tool like you might use on a hardinge lathe, if you only have RH tooling flip the tool 180* and bore on the other side of the ID turning in reverse. If you make the bar long enough you can clamp a weight or another tool holder on the on the portion sticking out the back to keep vibration down. Max DoC is about 30-40 a side so you can rough and do two finish passes if size is critical or two pass it. Hope this helps.

  5. #25
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    Everything helps. Thanks!

  6. #26
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    Quote Originally Posted by MattiJ View Post
    Something like that. Also pay attention what Digger Doug was writing..

    Mill the slots along the side of the bar and you can use your existing smaller boring bars or mill the slot in the end and you can use "normal" lathe tool.
    Even a 1/2" shank insert holder/boring bar would be enough big if you mount it to the end of large bar but 3" bar leaves plenty of room even for 1" tooling.

    Probably takes you less time to make one yourself than hunt for suitable one used... especially if you have to make the mounting block/clamp setup in anyways.

    We have several bars like that.
    Works very well, and easy to make. All sizes of course.
    But we always use TPMR16 holders, those work the best on our old lathes Boring bar selection questions

    Btw that picture has really got around the world. Seen it many 'places' Boring bar selection questions

    Colchester - The world turns on Colchester lathes.

  7. #27
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    Ditch the compound and make a mount that attaches directly on the cross slide. It will be way more rigid.
    You can also use for drilling with large drills using power feed.

  8. #28
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    I wouldn't make the compound end to fit a tool holder,it just adds more spring,bolting to cross slide or compound is the way to go.
    For a balanced bar just make it tee shaped.Before you weld the tool bit holder to the end you can easily mill the bit slots off set so the cutting tips are on the same center.

    If you use 2" or more square stock just use the same stock to make the end piece,there is ample width to mill 1/4-5/16 or 3/8" slots for brazed carbide bits and the offset exactly.

  9. #29
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    Epoxy alone would work fine (industrial specs and theory).

    Typical choice is 2 small bolts maybe 5-6 mm through the toolholder onto bar.
    A large 3-4-5" square steel blank, rounded a bit in the lathe, will give you an excellent base to bolt/epoxy toolholder onto.

    A 1000$+ purchase or 1/2 hour and 30$ in stuff.


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