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  • I make chips
    replied
    [QUOTE=PStechPaul;n2001288]What's the deal with these two versions?

    Same thing but different. One has a16mm shank the other 20mm. The bigger one takes bigger inserts.
    Well,, the brown 1 2 3 deal is actually different tip angles....
    Last edited by I make chips; 05-28-2022, 04:19 PM.

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  • J Tiers
    replied
    Originally posted by DR View Post
    As shown in post #19, the center one "H" is not something I'd use for boring since the non-cutting insert is going to be rubbing on the bottom of a blind hole. Okay to use for a through hole though. I always used single insert bars, spindle turn forward for ID boring, reverse spindle and OD turn on back side of part.

    Spindle reversal is no big deal on a CNC.
    What's the difference?

    With the others, the longer side is going to be doing "something" when the shorter side is in use. So it seems that all 3 types are each "limited" in some way (surprise!).

    And each of the 3 types will have an advantage in a specific situation, saving a tool position for some particular job. Makes sense to me. And, they could be useful for manual machining as well, even if only that you may not need to remove the tool between operations.... same thing as with CNC, just "in slower motion".

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  • DR
    replied
    As shown in post #19, the center one "H" is not something I'd use for boring since the non-cutting insert is going to be rubbing on the bottom of a blind hole. Okay to use for a through hole though. I always used single insert bars, spindle turn forward for ID boring, reverse spindle and OD turn on back side of part.

    Spindle reversal is no big deal on a CNC.

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  • Doc Nickel
    replied
    Originally posted by JRouche View Post
    He said he has never seen one of those. JR
    -I ran across one shortly after I got my gang-tool lathe, and was looking for cutters.

    I can only think of two reasons to use one: First, if you have a slow turret, I could see not having to stop and tool-change could save a small bit of time. And on a professional machine, if you're running 20,000 parts and save just two seconds a part, that can shave something like eleven hours off the total run time.

    Or, alternatively, you have either a very complex part, or a smaller turret or even a gang-tool lathe, and have limited space for tools.

    On my machine, so far I've never had more than four tools set up at once, two is more likely and I've done a couple using just the one. Looking in the manuals, I see recommended setups with eight to ten tools, so chances are I'm not going to need anything like that anytime soon.

    Doesn't mean others don't, though- and the simple fact they offer the three different versions- among other things, to cover machines that normally turn counterclockwise and ones that turn clockwise.

    Doc.

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  • JRouche
    replied
    I asked a friend of mine out in Conga Park , California. My go to. Mostly CNC though.

    He said he has never seen one of those. JR

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  • wierdscience
    replied
    [QUOTE=mtraven;n2001690]


    hmm...I suppose it could be the angle of the photo, but it really looks like that right insert is tipped down relative to the other. and I too can't think of a reason you'd want that on a cnc (you debunked my previous theory)...which is why its so perplexing...they also advertise as "up" & "down" --maybe just a marketing gaffe, i dunno. There are actually 3 varieties:


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    [QUOTE]

    Relief for ID facing.

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  • J Tiers
    replied
    You'd want it for negative rake inserts...... or neutral.

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  • mtraven
    replied
    Originally posted by Doc Nickel View Post
    -Nope. Looking at the high-rez copy you posted in #10, on a 27" desktop monitor. Close enough I can see the oil and lint on the bars.
    Close enough I can see those are diamond, PCD or CBN inserts. Andno, I'm not seeing either an angle or height difference.

    Thing is, there is zero reason to have them at a different angle, and less than zero reason to have them at a different height. No CNC machinist would want the inserts at different heights- on a CNC lathe, whether turret or gang, the center height is set manually, with shims or adjuster screws.

    hmm...I suppose it could be the angle of the photo, but it really looks like that right insert is tipped down relative to the other. and I too can't think of a reason you'd want that on a cnc (you debunked my previous theory)...which is why its so perplexing...they also advertise as "up" & "down" --maybe just a marketing gaffe, i dunno. There are actually 3 varieties:


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    I went through dorian's entire pdf of cutters, they have a bunch of 2 insert cutter like this & good profile drawings, non of them have height differences. But that pdf did confirm bented's theory about the "lead offset" for facing. That all stands in confirmation of what you've said, but my eye's see differently, even in the top view I see it.


    pdf was too large to upload, here's the link --page 82 is where the double insert bars start

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  • Doc Nickel
    replied
    Originally posted by mtraven View Post
    pretty sure I said that.
    -Yes, you did. But you also noted that if one wanted to use the upper tool on the "other side" of the bore, you'd have to reverse the spindle.

    Which is possible, yes, but is not what it's for- and I very much doubt anyone would bother programming such a thing, as the spindle reverse time would all but negate any time saved by not having to retract the tool and make another pass with the first one.

    there is also a length difference(likely for facing as Bented pointed out), but there is 100% also a height & angle difference. are you looking at the pics on a phone or something?
    -Nope. Looking at the high-rez copy you posted in #10, on a 27" desktop monitor. Close enough I can see the oil and lint on the bars.
    Close enough I can see those are diamond, PCD or CBN inserts. Andno, I'm not seeing either an angle or height difference.

    Thing is, there is zero reason to have them at a different angle, and less than zero reason to have them at a different height. No CNC machinist would want the inserts at different heights- on a CNC lathe, whether turret or gang, the center height is set manually, with shims or adjuster screws.

    With two inserts at different heights, you'd only be able to set one or the other- but not both- "on center". And why have two inserts on one bar if one can't be properly used?

    Nope, Bent is almost certainly right in that the long corner is for facing, but the inserts are otherwise at the same gage height and angle.

    Doc.

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  • mtraven
    replied
    -That's not what it's for. Again, theoretically you could, but there's no reason to. Barring further information, I'm quite convinced this for conventional turning on both the ID and OD of a part, using one tool slot in your turret or in your gang-tool array.
    pretty sure I said that.

    -First, it's a length difference. The insert height is the same, just that insert is slightly longer on the shank. I still don't really understand why, but there must be a reason.
    there is also a length difference(likely for facing as Bented pointed out), but there is 100% also a height & angle difference. are you looking at the pics on a phone or something? Not sure how your not seeing that. I do see your point about a height change though...so I really dont know.

    Nope, all four shown are the same size CCMT, it's just the angle in the image that makes it look a little different.
    I was referring to the placement of the inserts being symmetrical WRT the centerline.

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  • Doc Nickel
    replied
    Originally posted by Bented View Post
    Quite possibly for facing operations, I would not like to drag a secondary insert backwards across the part face.
    -Oh, had not thought of that, I suspect you're exactly right.

    Brain was stuck in turn/bore mode.

    Doc.

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  • Bented
    replied
    Originally posted by Doc Nickel View Post

    I'd be curious to know the official reason for that offset.

    Doc.
    Quite possibly for facing operations, I would not like to drag a secondary insert backwards across the part face.



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  • old mart
    replied
    I have used boring bars to turn external surfaces occasionally, when it was the best shape for ackward jobs, but having both right and left handed bars from 4mm to 25mm, a double headed one won't be in my wish list. One disadvantage of the double headed in a bore is that a larger shank and stiffer single headed one would do a better job in the same start size bore, I'm not up against the clock.

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  • Doc Nickel
    replied
    Originally posted by mtraven View Post
    but if you wanted to cut with the 2nd insert on the other of the bore, you'd still need to reverse the spindle.
    -That's not what it's for. Again, theoretically you could, but there's no reason to. Barring further information, I'm quite convinced this for conventional turning on both the ID and OD of a part, using one tool slot in your turret or in your gang-tool array.

    here's my guess: I think the height offset is more a consequence then a feature.
    -First, it's a length difference. The insert height is the same, just that insert is slightly longer on the shank. I still don't really understand why, but there must be a reason.

    Note the offset height bar also has asymmetrical inserts[.]
    -Nope, all four shown are the same size CCMT, it's just the angle in the image that makes it look a little different.

    the left most insert is for od turning & the right insert of the left tool is for ID work, that tip would let you bring the tool in above center allowing for better tool rigidity (more shank under it)
    -I'm not sure there's a reason to have different tool heights on a CNC turning center. I know on my gang-tool machine, there's not even an easy way to adjust it, on round-shank tools like this.

    But that's irrelevant- again, the two inserts are the same height, just different lengths on the shank. My best guess- and that's all that it is- for the reason for the length difference, is for boring. If the spindle is turning clockwise (in reverse compared to typical manual lathes) the "longer" insert can bore without worrying about the other insert accidentally contacting the end of the bore.

    Seems kind of odd it'd be for clockwise machines only- there's definitely plenty of those out there, but there's also an F-ton of gang-tool machines that turn counterclockwise like normal.

    I'd be curious to know the official reason for that offset.

    Doc.

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  • mtraven
    replied






    You do not have to reverse the spindle, simply move the tool at rapid speed.
    this works if your going from ID -> OD or visa-versa. but if you wanted to cut with the 2nd insert on the other of the bore, you'd still need to reverse the spindle. though you could design a tool that flipped the 2nd insert upside down, but with that you couldn't do what the other could.
    better view:

    here's my guess: I think the height offset is more a consequence then a feature. Note the offset height bar also has asymmetrical inserts, I think they tip them to keep the width of the bar minimum & a height offset is required to present the insert tangentially.

    OR

    the left most insert is for od turning & the right insert of the left tool is for ID work, that tip would let you bring the tool in above center allowing for better tool rigidity (more shank under it)



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