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Parting off relatively large diameter stock

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  • #31
    Originally posted by Yondering View Post
    I stumbled across this video that details mounting spacers to the chuck face for the same effect. I like the idea, seems like it would be very versatile, and should work perfectly for the OP's needs.

    https://www.youtube.com/watch?v=U3x8H1Xb-jg
    same. I immediately thought of Joe Pie when I started reading this thread

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    • #32
      an old machinist told me he would use wax to hold washers to a faceplate/chuck to face them down to thickness. make the cutter really sharp.


      aluminum at 3 inches might be a thermal expansion problem as the wax cools off and solidifies. if that's a problem you could fix it to an aluminum part and chuck the aluminum part in your lathe, rather than melting the wax to a cast iron faceplate or chuck face.

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      • #33
        The rail arting is impressive, but to be fair, the cutter is apparently a coolant-through type with high pressure. That likely makes the cutting part of the deal go much better than for all of us poor saps who drip oil on, or part dry.

        Still, the interrupted cut is a biggie, and a lot of rail is really nasty, hardening up if there is any rubbing or failure to cut.
        CNC machines only go through the motions.

        Ideas expressed may be mine, or from anyone else in the universe.
        Not responsible for clerical errors. Or those made by lay people either.
        Number formats and units may be chosen at random depending on what day it is.
        I reserve the right to use a number system with any integer base without prior notice.
        Generalizations are understood to be "often" true, but not true in every case.

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        • #34
          I agree a good insert holder like Seco should do it, but those things aren't unbreakable. Don't ask. The most important advantage that the insert holding blade has is that the insert is widest at the cutting edge, and the holder is only about 80% as wide as that edge. But still, any chips that don't clear will cause trouble. Sometimes you get a ribbon of swarf rolling up and not clearing the gap, and this helps to heat everything up, and BANG !

          My metal supplier has a large band saw. I'd ask him to cut some silces for me, and then I'd clean them up in the lathe.

          Firstly they use their saw every day, so it's adjusted straight, and secondly the blade is much deeper, so it's easier to hold a straight cut.

          If I didn't have a local supplier, I'd cut plate. If the slices could have a hole in the middle, or several holes elsewhere, I'd make a jig to mount them in the chuck. If no holes were allowed, I'd investigate holding them to a blank with hot melt glue or similar.
          Richard - SW London, UK, EU.

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          • #35
            In addition, most all the insert holder bits are formed to fold the chip inwards so that it is far less likely to hang up and jam in the cut. I have older insert holders, not the blade type, but the type that has a shank that changes into a blade out where the cutting occurs. One of them takes wide inserts, the other narrower, but neither will get close to a 4" round.

            Aside from those, I use all sorts of ground HSS tools similar to grooving tools, but again, none is close to handling 4" stock. I DO have several types of legitimate HSS cutoff blades, but have never made holders for them.

            Frankly, the saw will turn less of your stock into chips, and if it cuts straight, will not require a lot of facing to true up the part. It is a viable option, and that comes from someone who would rather part off, and will part off with whatever piece of junk cutter comes to had, if it looks like it will work.
            CNC machines only go through the motions.

            Ideas expressed may be mine, or from anyone else in the universe.
            Not responsible for clerical errors. Or those made by lay people either.
            Number formats and units may be chosen at random depending on what day it is.
            I reserve the right to use a number system with any integer base without prior notice.
            Generalizations are understood to be "often" true, but not true in every case.

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            • #36
              I would avoid parting off if there were any viable option. If forced to part off that diameter I would dig out my old lantern toolpost and use the straight Armstrong parting tool. Unless you have a really rigid lathe you want to avoid the parting tool hat fits the QCTP. They put the center of the tool way to the left of the centerline of the cross slide. That means when there is load on the tool it not only deflects downward it rolls to the left. That makes it bind, deflecting even more, binding more..... crash.

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              • #37
                In a case like this I'd look for someone with a large enough capacity band saw. There's too much 'pucker factor' in parting off with that diameter- lot easier to face the cutoff discs after the fact.

                This does bring up something to think about, for me anyway- what would be the difference in the stresses in the material between the cutoff disc and the cutout from sheet? Perhaps nothing to be worried about, but perhaps there would be an effect where one might be better to use than the other. In terms of how well it faces, or what it's like to turn the OD- perhaps the only real factor would be the alloy.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                • #38
                  Originally posted by darryl View Post
                  ...perhaps there would be an effect where one might be better to use than the other...
                  One can get a very nice face finish with sheet metal without the need for secondary operations.
                  12" x 35" Logan 2557V lathe
                  Index "Super 55" mill
                  18" Vectrax vertical bandsaw
                  7" x 10" Vectrax mitering bandsaw
                  24" State disc sander

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                  • #39
                    Doesn't look that difficult. Carbide insert blade in a good holder, just under 2" sticking out. Lock what you can (saddle etc), use cutting fluid and power cross feed, 4 thou per revolution. Put a blindfold on the Bridgeport so it won't see what's happening and get jealous. Then just go for it.

                    Holding the work in a 4 jaw is an excellent idea - much more clamping force.

                    Ian
                    All of the gear, no idea...

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                    • #40
                      For this type of work I used soft jaws and machine to fit the or with some luck had a set from a past job that work.

                      Dave

                      Originally posted by 01-7700 View Post
                      same. I immediately thought of Joe Pie when I started reading this thread

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