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How to cut short piece of huge stock

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  • How to cut short piece of huge stock

    I have a piece of cast iron I got for christmas. It is slightly over 4 inches diameter, and 2 inches long, and I need to cut it into a pair of 1 inch thick disks with non-horrible accuracy. I do not have a bandsaw. I do have access to a chopsaw with nowhere near the capacity needed, a small angle grinder, the lathe.

    I grooved it deeply in the lathe with the parting blade but even with the short extension it chattered badly. I have a hacksaw, of course, but it seems like this would take a very long time to do, and I seem to be very bad at using the hacksaw effectively.
    Any ideas other than finding somebody who has a bandsaw or hacksawing the thing?

    Also: My dad was freaked out about me having something that big in the 4 inch 4-jaw chuck in the lathe. It was spinning 100 rpm. He ordered me to have a rod in the tailstock chuck near the end so that if it came out of the jaws it would not hit me in the face or something even though it was only 100 rpm. Is this reasonable?

  • #2
    Cast iron should cut nice but you are probably limited by machine rigidity.
    Do you have a revolving centre and can you stand a hole in the end of one piece? If so centre it and support it on the revolving centre.
    If you can't stand a hole in it take a bearing and put that over the centre and push it onto the face of the work.
    This is a poor mans revolving centre.

    Any support you give the work will pay back 10 fold.

    Then try parting off as deep as you can go, you probably won't be able to get too deep because of tool limitations but remember you are removing more metal at the circumference than anywhere else.
    This will give you a groove that you can follow with your hacksaw in the vise.
    Don't be tempted to try sawing in the lathe unless you want a new forum moniker of "split nose"
    keep turning the metal following the parting off groove, cast iron cuts readily into dust, you don't need any lubrication as the graphite in the cast does it for you.

    .
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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    • #3
      Hmm...


      The piece is half as wide as long

      I did not think I would be able to center it but maybe if i overexend the tailstock...


      I was using cutting oil mainly to make the dust less messy and blob it up.

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      • #4
        This is one of those occasions where networking is very useful. You really need to borrow some time on a band saw. If that doesn't work out then a hacksaw is the next good idea and yep, it will take a while. In a pinch you can also use a reciprocating saw which are available for rental - a variable speed version is most suitable. An automotive machine shop may be able to cut it off for you at a very reasonable rate.

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        • #5
          Originally posted by Teenage_Machinist
          Hmm...


          The piece is half as wide as long

          I did not think I would be able to center it but maybe if i overexend the tailstock...


          .
          No it's twice as wide as long or at least 4" diameter by 2" long was when I went to school but that was a long while ago

          If you have already had it in the chuck and had a rod in the tailstock chuck why can't you centre drill it ?

          .
          .

          Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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          • #6
            OOps sorry..


            Actually there is enough clearance. I did not think there was. Tailstock out pretty far though

            NO luck. The chatter is extreme. Lathe not rigid enough> The groove is barely 3/8 deep if that. '

            Reciprocating saw? you mean like a saber saw or a sawzall? My dad has a sawzall but I never though of that. I wonder if he has a long enough metal cutting blade.

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            • #7
              100 rpm on a lathe the size you have will be a chatter box, that said... I have done what your trying to do on my 9 inch. Run as slow as possible, if you need to, see if you can snag a smaller drive pully for the motor. I kept several on hand with my setup just for the ability to do stuff like this. Some support on the TS side sure won't hurt and will provide a margin of safety as well as more stability.

              Tool geometry matters greatly here, the cutting edge really needs to be dead on parallel to the axis of rotation as well as having the tool itself at a dead 90. Any variation will cause the tool to pull to one side or the other. Center height and tool sharpness also count big time, your better off being slightly above center height than below.

              This job is a definite "Take your time" thing. Very very slow on the feed in, back out and clear chips/dust often. don't have to back out all the way. I ran 1/16" or 1/32" parting blades on my 9", never larger, as wider tended to be a bit much for the machine, especially with larger diameters.

              Partially cutting through with a parting blade then switching to a hacksaw or Recip saw would be a smart move. Yes it's a slow process, but the goal is to do what needs to be done, decently. Not to get er done fast. There really is no reason why one cannot get through that diameter of cast with a hacksaw, not only in a moderately timely fashion, but also with little problem in deviation beyond what one will lose from a parting blade. Patience and proper setup are the key. As others have said, do NOT try to saw in the lathe.

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              • #8
                Originally posted by Teenage_Machinist
                I have a piece of cast iron I got for christmas. It is slightly over 4 inches diameter, and 2 inches long, and I need to cut it into a pair of 1 inch thick disks with non-horrible accuracy. I do not have a bandsaw. I do have access to a chopsaw with nowhere near the capacity needed, a small angle grinder, the lathe.
                If it is 2 inches long and you want two 1" pieces you have a problem. The cut is going to use up materials.

                Can you chuck it and use a hack saw? Don't leave one spot in contact but drag the blade across as it revolves in your chuck?

                Clutch

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                • #9
                  I included kerf in my calcs.

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                  • #10
                    I'd hacksaw it. You'll go through more trouble and use up more time trying to find a better way to do it. You've got a hacksaw, you've got a vice ... I say have at it! I've cut my fair share of BIG stuff with a hacksaw. It isn't fun, but it teaches patience, if nothing else

                    Oil is not a good idea on CI, in general. Coolant is acceptable, but the oil tends to "glob up" as you say, and then you end up with an abrasive slurry that will dull your tool quickly.

                    Alternatively, find a friend who can do it for you. I'd be happy to cut it for you, but I don't think you'll want to pay postage all the way to Illinois, just to cut a piece of CI.

                    edit: you say "not horrible accuracy" - what is the final dimension needed on the discs? You'll probably need to shave a fair amount off after hacksawing to get a clean, square face

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                    • #11
                      Some ideas

                      -Metal blades for recip saw are cheap, so you could go that route since you have a groove to help guide the blade. The blade will have to be longer than the diameter you're cutting by at least the stroke of the saw (an inch or more). On a virgin cut, though, you might have problems getting a straight cut...

                      -Oil on CI (cast iron) causes all sorts of grief. It's messy to cut dry but that's how it's generally done.

                      -Sometimes you can help the chatter on a cutoff blade by putting a good support under the cutoff tool holder. I use a small homemade machinist's jack (basically a bolt with a turned-smooth top on the head, with two jam nuts) for this. But you have a deep cut so you may be out of luck trying a cutoff blade

                      -A hacksaw with the part NOT turning is probably your best bet. Note that hacksaw blades come in different teeth per inch, and you probably want the coarsest you can find for this. A real hardware store (maybe Ace or TruValue) may have some options here. Probably not Lowes and their ilk...

                      -Your dad has the right idea. A four-pound chunk of iron can put a real hurt on you even if it is only going 20 MPH. Also, you should be wearing at least eye protection and preferably a full face shield, since you are learning what works and what doesn't. Bad stuff can happen, though it usually doesn't, but you won't have time to put these on if something does go wrong (like a cutoff blade shattering and flinging a piece into you). This is one of those issues where you'll hear a lot of "don't worry, that's never happened that I've heard of" but if you're blinded you won't get to do much machining. It's a small probability but high penalty situation; better to be in the habit of being at least somewhat over protected than underprotected.

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                      • #12
                        Don't tell anybody but the guys on here that you got a 4" lump of cast iron for Christmas. Nobody else would understand. Me, I don't understand why Santa didn't bring me one.

                        I think the hacksaw might be safest. If you've already cut a groove with the parting tool then this will be a good guide. If you are game for parting it then facing it after the hacksaw should be no problem.

                        Safety first. Trust your Dad. I've lost more than one tip off a parting blade. They departed with a big bang and I never did find the tip.

                        Good Luck
                        Phil

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                        • #13
                          If you got access to a Sawzall you got the world by the tail !! I have one next to my lathe and use it frequently to do cut offs on the lathe. Get an aggressive bi-metalic and it should cut the cast iron like butter, albiet frozen butter If there is one tool I'd put on a pedestal it would be the Milwaukee Heavy Duty Diamond Anniversary Model Sawzall I got a few years back. Don't know why and the hell I waited so long to get one.
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                          • #14
                            I might get flamed for this but why not run the lathe in reverse, take your hacksaw, reverse the cutting direction on the blade, and try cutting it with the lathe running in reverse? If it grabs the blade, the hacksaw will fly away from you, not towards your nose... You should remove your splash guard unless you want a nice big dent in it.

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                            • #15
                              I cut and use small pieces like that all the time. I mostly cut them using a Milwaukee portable band saw but a hacksaw will work just as well. Here's how I do it...

                              Let's say I have a 4-inch round that is 1-inch in thickness and I want to cut it in half. First I scribe a cutting line around the circumference. Then I place it in an ordinary work vise clamping it on the cut ends just a little above centerline. Using the portable band saw, or hacksaw, I cut it until I get about 3/8-inch from center. I rotate the material and continue to saw until I get a cut all around the bar. This will leave about 3/4 - inch diameter of material in the center. To complete the cut, I put in a piece of broken saw blade on one side of the cut and put the material back in the vise clamping it at the old saw blade. Cutting it this way results in the material being held very rigid and therefore no binding of the blade will occur.

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