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  • Opinions on cutoff tools?

    I've been slowly trying to upgrade my assorted tooling lately and have been toying with the idea of getting an insert parting tool. I seem to find myself doing these sort of cut-off operations fairly regularly and find the standard HSS or carbide tipped ones to be OK, but prone to chattering and the occasional "catastrophic failure" while in use.

    I have used the blade type insert ones, like this:

    http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3

    that I borrowed from the machinist at work a few times and found it to be miles ahead of the standard blade type. Looking around, there is also this style (which I have never tried):

    http://latheinserts.com/1-2-INDEXABL...04GTN20016.htm

    Any opinions as to whether there is any clear advantage to one style over the other? Does one work better? I can see some theoretical increased rigidity to the second type, but that could be only theoretical, and there is the fact that the depth is a bit limited by the design. But again, that may be more of a theoretical rather than real limitation. Is there some other type I'm overlooking? Thoughts and opinions, please?

    Discuss.

    By the way of background, I just picked those two above somewhat at random as examples of what I was looking at. So I have no allegiance to either one. I'm looking to use this with either a 10x24 Jet lathe, or 10" Sheldon in AXA and BXA sized QC tool post.

    Thanks, and for those observing in the US, have a great Thanksgiving!

  • #2
    Happy Thanksgiving to you too.

    There's a couple of things to consider. With your AXA and BXA tool posts, you likely have the No.7 blade holders for HSS cutoff blades. These are useless for carbide insert tooling. My opinion is that when you get a tool that makes sense for your situation, you will never regret going with carbide insert cutoffs.

    With using the blade style on a QCTP, you gain being able to use a variety of widths, from 1.5mm (.059") up to perhaps 5 or 6mm. The most popular is the 3mm (nominal) at .118", they often cut actual .122" wide. That does require buying additional blades for the different width inserts. The key to not blowing them up is to rationalize the insert width to how big a diameter you need to cutoff. Don't attempt to cutoff a 1/8" diameter workpiece with a 5mm (.197") wide insert any more than you'd cutoff a 3" diameter one with a 2mmm (.078") wide one.

    Yes, the "monoblock" holders which can take the same inserts can be more rigid, but also more costly and limited. With a blade style, you could have the blade farther away from the block because of the holders. There are the No. 7-71 or No.71 style holders which are integral blade holders for direct to the toolpost, but I've not seen one in AXA yet. There are blade holder blacks that are clamped in a regular No.1 or No.2 holder, but those move the blade even further away from the support.

    The blades tend to be about the same money as a monoblock holder, but blades usually give you two ends/pockets for the price, in case you have an accident.

    In your case with two 10" machines you could use a 1/2" monoblock style in both, just be aware that the small monoblock tools are limited to cutting off perhaps 1" to 1-1/2" bars (or 1/2 that in wall thickness cutting to a bore.) With monoblock holders you can go to double-ended inserts for lower cost per edge. If interested, I may have a 5/8" holder for double-ended that I (or you) could machine an 1/8" off the bottom. Ping me via PM about it.
    Last edited by PixMan; 11-27-2014, 08:41 AM.

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    • #3
      I prefer the 2nd style. It is more beefy and you can clamp the inserts. You can do light turning with them as well. Both types work well. The main thing to remember is that parting tools can only go so deep before they will bind and break. If you need to go more than 1/2" deep you may want to seriously consider a bandsaw for that operation. Saw a little long and face to length.
      Last edited by Toolguy; 11-27-2014, 12:34 PM.

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      • #4
        Alan: Carbide is way better than straight high speed blades. The carbide inserts I have used cut a wide kerf so the blades have
        clearance through the kerf.

        The only thing, you are going to cry when you have a crash. I don't run very much production so I have a pretty conservative
        tool budget.

        I sure like the parting tool from Latheinserts.com. Looks like a nice tool for $35. I would like to order one.

        The parting tool from ENCO appears expensive. Seems like I ordered one of those .093 wide for $80. That kind of parting tool
        is probably the most robust and you get two insert holders per blade.
        Jim
        So much to learn, so little time

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        • #5
          There are a zillion options, all pretty confusing. I consider myself a novice at these, but here's how it went for me.

          One way to go, and a great place to start, is to use one of the insert blades that are designed to be compatible with traditional old style HSS blade holders. You could get one of those and just stick it in your existing AXA cut-off tool holder. I lucked upon just such a holder for cheap from a local seller, an Iscar SGHS 4-17-3 with 18 inserts. It is a somewhat wimpy looking thing, but it works great. If you watch ebay you might do well on a used one, or one of the variations from the other manufacturers. The geometry varies depending on the holder you'll be using it in. The SGHS uses a common insert that could be used in other cut-off tooling.

          In terms of the other solutions, I didn't like a lot of what I found - blocks, blades, blocks in holders, etc. But the Dorian 71C caught my eye as a great solution. I lucked out on ebay and found a couple at great prices (in CXA). But the SGHS has worked so well for me that I haven't gotten around to tooling up the 71C's. They apparently make an AXA version of the 71C, but it is a rare and very pricey thing. I think it would be a great DIY project.

          I found the SGHS is best power cross fed at the proper rate. That is likely true of any insert based cut-off tool.

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          • #6
            Not that I will ever get to this project but I'm sort of partial to ones similar to the blade of your first example...IF you have the ability to machine your own tool holders that match the wedge tool post size you have, consider just making one up yourself (as opposed to the 71C) but I would make it for a size of blade that is more common and so have a bit more choice of insert (perhaps, maybe, at some point down the road). I'd go looking for one of the more common blades sizes and styles/makers hoping to lessen consumable costs and easy the finding of inserts going forward.

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            • #7
              I found the following advice on the second type interesting:

              • [*=left]NOTE: MUST RUN .004-.005 ABOVE CENTERLINE TO PREVENT WORKPIECE FROM RIDING ON TOP OF INSERT AND BREAKING TOOL.


              I had always heard that it must be dead on center, but in my experience and opinion it is better to run it a tad below center rather than above, as advised here. But this may depend on how the tool is sharpened, and positive rake (or chip-breaker notch) on the top edge may cause it to grab and dig in. Running above center will eventually have the tool face rubbing on the small diameter "nit" that remains, while below center will just cut at a sharper angle until it reaches 90 degrees and passes under the "nit" or "nub" or what ever you may call it.
              Last edited by PStechPaul; 11-27-2014, 06:56 PM.
              http://pauleschoen.com/pix/PM08_P76_P54.png
              Paul , P S Technology, Inc. and MrTibbs
              USA Maryland 21030

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              • #8
                Alan,

                I have the Dorian version of the first one and love it. I regularly cut 2" steel with it and have never had a problem. The inserts seem to last forever. It came with the lathe when I bought it used about 5 years ago and I am still using the same insert that was in it when I bought it.

                A few months ago I had a job where I turned a bunch of nylon up to 4" diameter and the parting tool was handy for the deep cuts that I needed to make. The one in the second link doesn't look like it would cut anything over maybe 2" in diameter.

                I have priced out the inserts for the Dorian cutoff tool and they are fairly expensive buy like I said they last a long time so no worry there.

                Back in the day I used a lot of HSS parting tools and they worked OK as long as you had a good solid lathe to use it in and sharpened it square.

                Brian
                OPEN EYES, OPEN EARS, OPEN MIND

                THINK HARDER

                BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

                MY NAME IS BRIAN AND I AM A TOOLOHOLIC

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                • #9
                  I like both - the first is marginally better.

                  I prefer these - expensive - just sharpen on a standard pedestal grinder using the gauge provided - also see the 60 deg screw cutting tool:

                  http://i200.photobucket.com/albums/a.../I-Fanger3.jpg

                  http://i200.photobucket.com/albums/a.../I-Fanger2.jpg

                  http://i200.photobucket.com/albums/a.../Part_off4.jpg

                  http://i200.photobucket.com/albums/a.../Part_off1.jpg

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                  • #10
                    Originally posted by PStechPaul View Post
                    I found the following advice on the second type interesting:

                    • [*=left]NOTE: MUST RUN .004-.005 ABOVE CENTERLINE TO PREVENT WORKPIECE FROM RIDING ON TOP OF INSERT AND BREAKING TOOL.


                    I had always heard that it must be dead on center, but in my experience and opinion it is better to run it a tad below center rather than above, as advised here. But this may depend on how the tool is sharpened, and positive rake (or chip-breaker notch) on the top edge may cause it to grab and dig in. Running above center will eventually have the tool face rubbing on the small diameter "nit" that remains, while below center will just cut at a sharper angle until it reaches 90 degrees and passes under the "nit" or "nub" or what ever you may call it.
                    I always set my parting tool (sometimes the threading tools well) at least 0.005" above centre - 0.020" on bigger jobs is OK too.

                    A parting tool as well as a screwing/threading tool is a "form" tool after all.

                    These tools are inclined to "dive" down under load and setting the tool higher gets it back closer to being on centre under load.

                    A maths check will soon show that any change to the formed/turned part is minimal to the point of being inconsequential - same applies to tilting the screwing tool left (or right) to set the tool parallel to the thread helix (angle).

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                    • #11
                      I have the exact model in first pic,seems to work good a nice upgrade from HSS.I got a bunch of inserts for that model at auction 25 cents a piece so no brainer to go with it.Blade,holder and tool for install and removeal of inserts $250.00

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                      • #12
                        Thanks for the replies, guys. Lots of good info here.

                        The flat blade type was the sort I had used, and it did seem a huge upgrade from the standard blade type. With the awareness that crashes are more costly, hopefully the increased cutting efficiency will make crashes pretty rare. I guess that is the general deal with insert tooling. I have a few rather nice insert turning holder that cut great but give me two edges for about 7 bucks. So bashing one is costly, but they work so well that I tend to avoid wrecking them. I still use plenty of HSS ground tools that I use for much of what I do.

                        Tiffie, those are different, I have not seen that style before. Interesting, thanks for the pics.

                        Sounds like the blade style may be the way to go. Nothing says I can't get both I suppose, but like a typical HSM type I prefer versatility and limiting cost somewhat is nice. Even if this only worked on the BXA post, that would be a good start. From the look of it, it would not be too difficult either make an AXA holder approximating the Droian 71C that Glug mentioned. I suppose it might not be too difficult to modify a cheap AXA holder of some other type to do the same thing.

                        PS - Pixman, will send you a PM on the double ended holder. Thanks!

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                        • #13
                          When I owned a 9" South Bend, parting off was very frustrating for me. However, I found a good solution. I bought 2 kits from Metal Lathe Accessories (?), namely:
                          http://www.statecollegecentral.com/m...he/S-4382.html
                          http://www.statecollegecentral.com/m...the/MLA-6.html

                          The upside-down rear-mounted toolpost made all the difference for me. I suspect you will also experience rigidity problems with a 10" lathe. Maybe these kits would help for you. BTW, it is an option to pay MLA to have the parts machined for you.

                          metalmagpie

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                          • #14
                            Setting a cutoff tool above or below center is just masking a bigger problem. If you're setting one .005" to .020" (0.13 to 0.5mm) above center because it'll push the tool down that much, you must have one very loose spindle or incredibly weak tool post. Fix that problem first.

                            The tools run just fine on center to no more than .002" or .003" above. Never really below because it could leave a bigger cutoff nib than necessary.

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                            • #15
                              What is the best position when cutting off a hollow cylindrical piece? This may be tricky if the hole is rather large, like a piece of pipe, and especially if the bore is not quite concentric or has a weld line inside? I think it may be safer in such cases to run the tool below centerline so that it has essentially negative rake and the remaining piece will glance over the cutting edge or cause it to deflect down and away, rather than dig in and jam. But the safest way may be to use the parting tool to cut a groove almost to the inner surface, and finish cutting with a saw, followed by facing or otherwise cleaning up the edge.
                              http://pauleschoen.com/pix/PM08_P76_P54.png
                              Paul , P S Technology, Inc. and MrTibbs
                              USA Maryland 21030

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