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Near miss .... not so gentle parting reminder

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  • Near miss .... not so gentle parting reminder

    This past weekend I was parting off a short length of 2" aluminum round and all was going well until the tool dug in and 1/2" of the front end of the tool was literally torn off (good HSS, US made) and flew somewhere at high speed. The 2" stock was torn from the jaws of the chuck and has about a 1/4" deep gash where it was held.

    Not much stock was protruding from the chuck but unfortunately, only about 1" was held by the chuck ... dumb, but still have 2 eyes, 10 fingers, 2 ears and 3 nostrils

  • #2
    Geez, yes, I noticed that with the drill press, drilling with HSS and the drill chips or breaks or partly shatters, the pieces become shrapnel. You parting tool just that much more dangerous.

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    • #3
      Ya never konow. This afternoon I was doing some wiring in the shop. I snipped the end of a piece of 10 ga. copper wire and it parted with enough force that the cut off piece hit the wall fifteen feet behind me. Wouldn't have liked to have caught that one in the eye!

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      • #4
        <font face="Verdana, Arial" size="2">Originally posted by x39:
        Ya never konow. This afternoon I was doing some wiring in the shop. I snipped the end of a piece of 10 ga. copper wire and it parted with enough force that the cut off piece hit the wall fifteen feet behind me. Wouldn't have liked to have caught that one in the eye!</font>
        That's funny,I just disconnected a 10 ga copper wire today,only realised I didn't have the disconnect tripped on the 440vac buss duct

        Funny too are parting blades,I have never snapped one.....everybody else does it for me I leave Friday,Monday I come back and there are only pieces,that's why I hide them now

        I just need one more tool,just one!

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        • #5
          Better carefully check out your 3-jaw. They're fragile and ripping out a hunk of material in a wreck is almost a sure recipe for springing the jaws and deforming the scroll.

          I don't intend this to be taken as a vindication but it's not for nothing that I preach the use of a 4-jaw chuck for all but finishing operations.

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          • #6
            My favorite parting tool is the bandsaw.
            Free software for calculating bolt circles and similar: Click Here

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            • #7
              I am with Evan. I hate to part off any thing.
              I have a job making some 3/4 square nuts and I think that I will band saw them unstead of parting them off. Hate that bump,bump.
              Don\'t ask me to do a dam thing, I\'m retired.
              http://home.earthlink.net/~kcprecision/

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              • #8
                Somewhere in the past few days, I added my few pennorth about parting off. Again, in Spherical Turning on the "Other Channel" there was a photograph of an excellent parting off tool. It seems a pity that the considerable research which has gone into the once Black Art has been ignored.

                Whilst it is true that it can be sufficiently nerve wracking to warrant either hacksawing in the lathe or transfering to a motorised "parting off" band or hacksaw, it is a fairly simple operation.

                It would help if the topics hadn't such daft headings to refer! I have raised it on more than one topic!

                At this May's Harrogate Show, one of the old hands gave a demonstration of parting off using a tool holder which gave a little under load thus springing away from the cut.

                Again, I have suggested that mounting the parting tool upside down at the rear of the saddle is the prefered method. I don't subscribe to the School of Moaning Minnies who complain that their saddles don't have T slots. I fitted a sub table- complete with rear parting tool on a Taiwanese
                " whatsit" 918 lathe and this crap bag- your opinion- worked far better than your All American,All Singing, All Dancing, American contributions to the World of Excellence. I'm having a "pissed off"day!

                I went on to remark that my little tool holder was mounted up side down, was using a blade 3/16th thick, though it could be 1/16th, and would cheerfully part up to 2" stuff in steel.
                True, it is inclined at 7 degrees - Downwards - but is angled at 70 degrees to accomodate. It should have a 140 degree groove along the blade and should have the cutting edge- chamfered.

                Sounds like rocket science- but it is a tried and tested method for small lathes which are long past the first flush of youth.

                Does this sound too complicated to grasp or is this because the average American worker is too tight arsed to spend a few coins on a British book about a bit of machinery?

                Like Nelson as he faced the French guns for the last time said " For what we are about to receive, may the Good Lord make us thankful"

                Norman



                [This message has been edited by NORMAN ATKINSON (edited 06-22-2005).]

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                • #9
                  I snapped off the blade on my parting tool about a year ago. First time in a decade. I haven't bothered to regrind it. I'm not quite sure why I should. I haven't missed it a bit. Parting is a final operation and is very easily moved to another machine.
                  Free software for calculating bolt circles and similar: Click Here

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                  • #10
                    nheng's problem is not a result of lack of rigidity, but when making a deep cutoff, especially in aluminum that can expand due to heat, it is a good idea to retract the tool, and widen the cut as it becomes deeper. This will prevent expansion and grabbing.

                    The rear mounted cutoff tool is an improvement for the smaller, less rigid lathes as it redirects the cutting forces, allows the chip to fall away rather than bind, and is much more rigid.

                    A solid, one piece cutoff holder will accomplish much the same in these lathes.

                    I don't feel a diatribe against the American machinist is needed. Metal Lathe Accessories offers a nicely made casting that will replace the cross slide on South Bend and Atlas lathes, and is easily modified to fit other lathes of that ilk, adding to their usefulness and rigidity.
                    http://www.statecollegecentral.com/m...the/index.html

                    The rear mount cutoff tool has been presented in Home Shop Machinist several times as well. It is nothing new or magical. It is a good addition to the small lathe.

                    Many of the problems encountered with cutting off in the lathe stem from not feeding fast enough, rather than too slowly. The advice often given is to slow down, use back gear, etc. The best method is to watch the chip, and follow it in.

                    The smaller bench lathes such as South Bend and Atlas do lack rigidity and make use of a cutoff tool problematical. Add the lack of a power infeed, and the difficulties increase.

                    Practice and some care in set up is needed, but cutting off is quite possible in these lathes. It is another tool that should be mastered to get the most out of your machine.
                    Jim H.

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                    • #11
                      <font face="Verdana, Arial" size="2">Originally posted by JCHannum:
                      nheng's problem is not a result of lack of rigidity, but when making a deep cutoff, especially in aluminum that can expand due to heat, it is a good idea to retract the tool, and widen the cut as it becomes deeper. This will prevent expansion and grabbing.</font>
                      So what I thought was a slimy hack when I was doing it is actually the correct way to prevent dragging and breakage? Wow - sometimes I get lucky...
                      The curse of having precise measuring tools is being able to actually see how imperfect everything is.

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                      • #12
                        Are you guys parting off a piece of solid stock?
                        And is that common in a machine shop?

                        I learned the hard way about that one while making an MT2 arbor - no one got hurt and the cutting tool hit the ceiling when it came unglued.

                        Since then I only use the cut-off on stock that has a center hole.
                        Or . . . cut it down a ways, turn off the lathe and use a hacksaw to go the rest of the way.
                        C9

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                        • #13
                          Any cutting tool can break. I worked with a guy who was cutting a small gauge copper wire, like # 18 or smaller, with a pair of name brand wire cutters. Something he had done thousands of times before. And they broke. The broken cutter flew into his eye. He was lucky he was not blinded.

                          Why a piece of copper that was less than 0.1" in diameter broke a hardened steel cutter, I could never figure out. But it did happen.

                          ALWAYS wear eye protection. ALWAYS.

                          Paul A.
                          Paul A.

                          Make it fit.
                          You can't win and there is a penalty for trying!

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                          • #14

                            Yup, I was pollishing a custom alum drawer handle that I made from scratch. I had about 4 hours of work into it (Milling, drilling, taping, sanding, then finally buffing/pollishing).

                            I was happy as a fly in dung at the shine I was getting on my buffing wheel. I was _almost_ done and then all of a sudden, the drawer handle got sucked out of my fingers, went inbetween the buffing wheel and my bench, and shot across the shop.. The force of the buffing wheel smashing it onto my bench (My welding bench with 1/4" plate on top) caused a massive gouge in the handle.. All that work down the drain because I wasn't paying attention on the buffing wheel... Oh well..

                            -Adrian

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                            • #15
                              I was putting new universal joints in my truck last saturday. While removing one of the retaining clips, it went airborn and drew blood on my partners upper arm a few feet away. Just another reminder to take safety precautions wheneve you're in the shop.
                              Arbo & Thor (The Junkyard Dog)

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