Safety Question

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  • pntrbl
    Senior Member
    • Aug 2006
    • 864

    Safety Question



    Long story how I got in this mess, lol, but here I am. I need to lengthen the register/clearance area on this backplate. It's .025 from bottoming on the spindle like it's supposed to, but since I did the original work in my 3 jaw I'm wanting to set up in a 4 jaw to get concentric for the cut.

    This big 10" is the only 4 jaw I currently have mounted. This backplate will solve that issue BTW because it's for a sweet little 8" I got from BadDog that's much appropriate for an 11" bench lathe.

    As you can see I'm having a jaw problem. If I go with the middle step on the jaws there's too much extension. Won't clear the bed. But I can't go on the outer most step because then all 4 jaws run into each other before they reach the piece.

    So I compromised!

    It's tuned in to under .0005. Planning on 360 rpm to cut about a quarter of an 8 tpi thread out. Should I throw the switch?

    SP
  • Fasttrack
    Senior Member
    • Jul 2005
    • 6300

    #2
    If you throw the switch, i wouldn't want to be standing too close to it ... and i'd be taking very light passes ...

    I'm curious to see what others have to say ... if everything went the way its supposed to i can't see how its any different than having a solid jaw. BUT if you try to hog out to much or its not tightened all the way and it slips then you end up flinging a chunk of metal out ... so the cost/benefit ratio changes!

    360 rpm doesn't sound too horrific though - any chance at moving slower?

    Comment

    • pntrbl
      Senior Member
      • Aug 2006
      • 864

      #3
      Originally posted by Fasttrack

      360 rpm doesn't sound too horrific though - any chance at moving slower?
      I just did the math and I probably should slow down. I think a 2.25" bore at 360 rpm is around 180 sfm. Half that should be fine for cast iron.

      No wonder I was smoking the garage the other day .....

      SP

      Comment

      • pntrbl
        Senior Member
        • Aug 2006
        • 864

        #4
        Plan B

        What if I cut the packing pieces down to a size that doesn't stick out past the jaws? That would certainly LOOK a lot less dangerous.

        SP

        Comment

        • lwbates
          Member
          • Nov 2007
          • 78

          #5
          4 jaw

          pntrbl,
          If you could use some spacer blocks the same thickness, but smaller in the other 2 dimensions it would be safer. The amount of extra metal in the blocks that extend beyond the jaws is just extra mass that's trying to fly outward from centrifugal force, thereby trying to lever the work out of the chuck. The excess metal that extends beyond the sides of the jaws in the plane of rotation is trying to open the jaws at speed. Maybe some saw work?
          Lwbates

          Comment

          • Fasttrack
            Senior Member
            • Jul 2005
            • 6300

            #6
            Yeah i would think that somewhere in the 100 to 150 rpm would be good. I think the recommended SFM for cast iron with a HSS cutter is 60-80 which, at 2.25 diameter, is about 100 rpm. Not sure what your using though - if you have carbide i guess it needs to be faster. Don't have those memorized but i'm working on getting HSS with various materials memorized.

            Comment

            • Fasttrack
              Senior Member
              • Jul 2005
              • 6300

              #7
              centrifugal force...? There's no such thing ...

              Technically there is only the centripedal force mainting the circular path; the percieved force trying to deviate from the circular path isn't a force at all but the bodies inertia that you are feeling.

              Comment

              • pntrbl
                Senior Member
                • Aug 2006
                • 864

                #8
                Now don't get "physical" on me FT! LOL! I ain't smart enough for that. But I will cut them spacers as lwbates suggests and drop some r's. And maybe wear a helmet ......

                SP

                Comment

                • Fasttrack
                  Senior Member
                  • Jul 2005
                  • 6300

                  #9
                  Sounds good!

                  Nice looking lathe by the way! Looks like its brand-new. Did you just restore it? I know i saw a nice rebuild on here a while back but i can't remember now whose it was.

                  Comment

                  • Mark Hockett
                    Senior Member
                    • Apr 2001
                    • 976

                    #10
                    pntrbl,
                    I know this might be more work but you could machine a threaded arbor that threads in about half the depth of the back plate, mount the threaded arbor in the 4 jaw with the jaws oriented a little safer, screw on the back plate and center, then machine your register/ clearance area.
                    Mark Hockett

                    Comment

                    • Joel
                      Senior Member
                      • Jun 2001
                      • 3228

                      #11
                      Why even consider spinning a questionable setup at 360rpm?
                      For a short cut in forgiving cast iron, who gives a hoot about 'proper' SFM and the like. Production rates, tool wear, etc, mean nothing here.

                      I have done many things that I perhaps shouldn't have, but with silly slow speeds and feeds, have come through them all unscathed.
                      Every once in awhile, a sharp tool with plenty of rake, minimal DOC, light feed, and very slow speed is the fastest way to get a job done.
                      I definitely agree with using a more appropriately sized piece for the packing. You can also use some thin, double sided tape to discourage anything from slipping.

                      Good luck!
                      Location: North Central Texas

                      Comment

                      • winchman
                        Senior Member
                        • Aug 2003
                        • 4030

                        #12
                        Since you did the original work in the 3-jaw, there's got to be some orientation of the part in the same chuck that will give you acceptable concentricity. I've gotten into the habit of marking any part I make in the 3-jaw, so I can put it back in the same orientation.

                        I'd go back to the 3-jaw, and try to find the orientation you used previously. Those blocks look risky to me, especially the part that extends past the part toward the tailstock.

                        Maybe you could cut a notch in the blocks to fit over the jaw and eliminate the overhang.

                        Roger
                        Any products mentioned in my posts have been endorsed by their manufacturer.

                        Comment

                        • Your Old Dog
                          Senior Member
                          • Dec 2004
                          • 7269

                          #13
                          I got a friend who lives in California and I know damn well they got Duct Tape !! At those slow speeds and no other way of getting the job done here's what I'd do. I'd leave it as you got it, do about 4 turns of Duct Tape and at slow speeds I'd have a go of it. Here's the important part, I wouldn't boast about how you did it on this forum

                          BTW, the duct tape goo cleans up nicely with Goo Be Gone cleaner. The blood, if any, should hose off easily if you don't let it dry !

                          Can we assume you have you tried turning the jaws around in the chuck and you didn't have enough bite left?
                          Last edited by Your Old Dog; 01-09-2008, 05:24 AM.
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                          Comment


                          • #14
                            As was mentioned,Reduce size of blocks, slow speed, Etc.

                            Your real problem is ......

                            Throwing FLAMMABLE fluid on an electrical Outlet. Duh !

                            Worst thing about it is it won't catch on fire when you are standing there, It will drip in when you are sleeping,I can't believe I am the only one to notice. At least Duct tape it .

                            I am a Prick when it comes to safety.

                            Comment

                            • J Tiers
                              Senior Member
                              • Jan 2004
                              • 44281

                              #15
                              Essentially you have shimmed the part. That's not a problem.

                              The shims you have are too big as mentioned. Slowing down will be good.

                              And, an aadded point.....cast iron is the ONE material which will tolerate too slow the best...... The chip formation isn't very different at any speed. So slow won't hurt you.

                              BTW, the "register" won't/can't get you that super location repeatability that many claim anyway, so I wouldn't get too crazy about the perfection of it. I assume 1007 people will flame me for that, but I don't care.
                              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.

                              Comment

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