Unusual lathe boring bar

[Doc Nickel]

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.

[mtraven]

-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:





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

[J Tiers]

You'd want it for negative rake inserts...... or neutral.

[wierdscience]

[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:




[QUOTE]

Relief for ID facing.

[JRouche]

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

[Doc Nickel]

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.

[DR]

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.

[J Tiers]

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".

[I make chips]

[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....