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Fly cutter extension - death or glory?!

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  • Fly cutter extension - death or glory?!

    I want to ask advise before I do something that is almost certainly a bad idea. Will it work or will it kill me....that, is the question!

    I have a 3MT fly cutter that takes a 10mm left-hand lathe tool. It's currently got a CCMT for aluminium in it and it makes a lovely job of aluminium and also or Mopane - a hard wood from South Africa. I've used Mopane once before for making a small drill bit stand but now I want to make a larger one with enough space for metric fractional sizes as I start collecting them. The piece I have is nominally 6"x6"x2" and I want to face it in one pass to avoid the step I know my slight head nod will give - this is another thing I have to get round to resolving. To take it in one pass I'd need to extend the cutting tool so it's only held on one set screw - this is clearly a bad idea and definitely falls into the 'will kill me' category. I can't find longer insert tools that are 10mm shank - definitely not in my price range at least.

    I was thinking about drilling and tapping the blunt end of the tool, through-drilling a clearance hole through some 10mm square rod and then joining the two with some threaded rod and a jam-nut. The extension would need to be 40mm long to fill the slot in the fly-cutter but I was thinking to go as long as I could to act as a counter-weight. 100mm would be about right but I don't think I can drill a hole that long.

    Would it work well enough to be safe and stay rigid enough to give a decent finish? This wood is hard and machines more like metal by the way: http://www.wood-database.com/mopane

    Many thanks guys,

    Gareth

  • #2
    Gareth
    Don't do it, don't even think about it. Can't say I've heard of Mopane, but if it is wood, then take 2 passes and finish by sanding it.

    Of course, you could always adjust the head, you are going to have to do it sooner or later.
    'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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    • #3
      I pondered a adjustable fly cutter, and I have some smaller ones with plenty of mass and sliding sections that I can deploy, but for single sweep on large castings I made this.
      Meet the spinning surfacing wheel of death*. I'll get around to making a insert holder for it too one day.


      *It's never actually killed anyone in operation.
      Last edited by MrFluffy; 04-24-2018, 08:33 AM.

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      • #4
        I'll just leave this here.

        I hadn't had to bore a big hole before and didn't know I needed opposite hand boring tools for that, so there I was looking for a quick solution. Found one.

        Sent from my SM-G930W8 using Tapatalk

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        • #5
          Wow! Now that is scary.

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          • #6
            Originally posted by Richard P Wilson View Post
            Don't do it, don't even think about it. Can't say I've heard of Mopane, but if it is wood, then take 2 passes and finish by sanding it.
            Of course, you could always adjust the head, you are going to have to do it sooner or later.
            I know. I've shimmed it once and improved it but it needs a slightly different size shim. It's one of many things on my 'get round to it' list. I need to strike some sort of balance between just fixing up and improving the machines and actually using them though....and I'm in dire need of producing something I can be pleased with. The fly cutter gave such a good finish on this wood that I swear you could use it as a surface plate...which is why I'm loathe to do it in two halves and try sanding it if I can possibly avoid it.

            Originally posted by MrFluffy View Post
            *It's never actually killed anyone in operation.
            I should hope not....imagine the splatter!
            I like the disc, I'm just not sure how I'd get an insert attached without adding more off-centre mass than my mill can handle...which probably should stop me trying to think of other ways that are bound to have the same problem....but it probably won't!

            Originally posted by mattthegamer463 View Post
            I'll just leave this here.
            I hadn't had to bore a big hole before and didn't know I needed opposite hand boring tools for that, so there I was looking for a quick solution.
            I like the out-of-the-box thinking! I was going to say that you could just run it in reverse but then I realised the arbour might unscrew.
            I can't mount my fly cutter like that because it's 3MT rather than straight shank. I could though get a CCMT/CCGT inserted boring bar to fit in the radial socket of the boring head for this one-off (yeah, that's the plan!) use and have a useable boring bar as a by-product.....except there don't seem to be 12mm left handed boring bars available for sensible money. Hmmm, need a bigger mill, that's the solution! How much does divorce cost again?!

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            • #7
              Or you could make one. But at full extension on the tool shown, it won't go over 600rpm without shaking the mill off the floor. I plan to make a longer one just for the counter balance.

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              • #8
                It sounds like you need a Planer.

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                • #9
                  Originally posted by KiddZimaHater View Post
                  It sounds like you need a Planer.
                  My neighbour has a planer thicknesser but this stuff seems to be too hard for it. The blades seem to bounce - or at least that's what the finish looks like.

                  CCWKen: I keep thinking of it but keep coming up with issues - mainly with insert geometry/rake etc. I've not experience with TCMTs but they do look like they'd be easy to do a half-pocket for. Is the finish good? Does yours keep the bar horizontal? What angle is the insert at?

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                  • #10
                    Originally posted by Cenedd View Post
                    I like the disc, I'm just not sure how I'd get an insert attached without adding more off-centre mass than my mill can handle...which probably should stop me trying to think of other ways that are bound to have the same problem....but it probably won't!
                    You can just bolt a weight into the hole 180 from the cutter but not quite to depth, then its quite balanced, much more so than hanging out a boring head cutter to one side. I was originally going to make a lot of cutters the same and put them into each hole for a giant multi toothed face mill, but I needed a flycutter first and I've never revisited it.

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                    • #11
                      Check out the fly cutter sold by Suburban Tool. It has an extremely large swing. I wouldn't be comfortable with it on my BP, but on a heavier machine it id probably OK. For light cuts on wood your proposal will probably be fine.

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                      • #12
                        Originally posted by Cenedd View Post
                        I like the out-of-the-box thinking! I was going to say that you could just run it in reverse but then I realised the arbour might unscrew.
                        I can't mount my fly cutter like that because it's 3MT rather than straight shank. I could though get a CCMT/CCGT inserted boring bar to fit in the radial socket of the boring head for this one-off (yeah, that's the plan!) use and have a useable boring bar as a by-product.....except there don't seem to be 12mm left handed boring bars available for sensible money. Hmmm, need a bigger mill, that's the solution! How much does divorce cost again?!
                        I found this one;

                        https://www.ebay.ca/itm/1pcs-S12M-SC...8AAOSw8vZXOQxP

                        CCMT09 is a nice insert size, I find. My boring head has 1/2" holes, but maybe I can get away with it. Worst case, I turn it down and make a sleeve to bring it up to 1/2". Doesn't have to be on centre or anything so it's an easy job.

                        If I cut the 125mm bar down for backside clearance, I can make a few stumps of 1/2" rod to insert in the opposite end to attempt to balance it. And keep the RPM sensible, of course.

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                        • #13
                          I really don't think that using any sort of extended or longer holder is going to serve you well. It will just increase the amount of vibration be being way out of balance. Also the long skinny insert holder is going to flex and vibrate and may very well result in a poor finish.

                          With a smaller and lighter mill your lack of equal balance and the need for a higher RPM than is used with metal will be the killer. If you plan on doing enough of these things I would say it is time to make up something specific. Something with two equal length arms and two cutters which you will then do "something" to ensure they can hold inserts at the same cutting points or some way to use HSS and grind, or at least hone them so they match for diameter and depth. The resulting wide cut tool could also serve for use on aluminium.

                          I know you don't have the confidence and likely not the range of movement in the compound to make your own MT shank tools. But if you start with a Morse taper machinable stub it could be the basis for adding on the top of the "T" in some manner. Or perhaps start with a MT shell mill arbor and make up an arm to suit. It would also be a good way to justify a shell mill for larger work.

                          There's another issue to consider. A smaller size cutter will have more steps. But a much smaller size cutter will have many more steps but they will be very small steps. The height of the steps or coving produced by any out of tram error being scaled to the swept diameter of the cutter. So a lot of passes with a smaller cutter will actually be "flatter" than a couple of passes with a large size. And with small steps or shallower waviness it would be easier to sand the face to achieve a nice looking finish. That may be something for you to consider as well.
                          Last edited by BCRider; 04-24-2018, 02:54 PM.
                          Chilliwack BC, Canada

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                          • #14
                            Hmmm.... I know you don't have a lot of fancy indexing tools at the moment. The "something" to match up the cutters if you use short bits of HSS in the arms could be some manner of file rest that lets you use a diamond "file" or one of the diamond folding style sharpening tools like a file. Basically a set of pins with rolling tubes on them that act like a file rest for two directions and that includes a way to set the face of the HSS tool to "index" it.

                            In use you would start with regular grinding to get the tool bits roughly matched. Then you would hone off only a little to produce easily done secondary edges that match precisely.

                            The other option would be to make up your cross bar and fit it to the MT arbor and then rig up a temporary jig to allow you to machine spots for inserts at the ends. The MT arbor could be set down into a "V" block that is shimmed and clamped so when you flip the fly cutter assembly it settles back in exactly to the right position for cutting the other insert seat.

                            This is actually quite doable for you even with your present modest tooling and confidence level. If you are having trouble visualizing how to do this we could certainly aid you. But the actual work would not be all that bad to do and quite within your shop's present ability.

                            There is also very much something to be said for a design which is much like MrFluffy's "Spinning Wheel of DEATH ! ! ! " style of large wheel. The extra material starts out by acting as a flywheel to reduce the force of the impact from the interrupted cuts. It is also very stiff and won't bend. And if the design is done well it could even be considered more safe because you'll touch the spinning edges instead of the ends of a flying bar. At worst it might ding your knuckles a little. At best it would push your skin out of the way with little risk of a cut or bash. It just depends on how well you do your design to inlet the inserts.
                            Last edited by BCRider; 04-24-2018, 03:09 PM.
                            Chilliwack BC, Canada

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                            • #15
                              Originally posted by Richard P Wilson View Post
                              Gareth
                              Don't do it, don't even think about it. Can't say I've heard of Mopane, but if it is wood, then take 2 passes and finish by sanding it.

                              Of course, you could always adjust the head, you are going to have to do it sooner or later.

                              X2 - never hang a tool cutter out by one screw - never, you may be sorry even before it contacts something as centrifugal force alone might have it's way with it,

                              it's wood so yeah two passes and a quick sand with the grain blends everything in, if you need longer then build your own tool that excepts the insert cutter,,, just follow your old design and make it longer... always slow RPM's with flycutters as tip speeds are still very fast and so can also bring up the out of balance factor...

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