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Is this a safe setup for an interrupted cut on heavy part?

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  • #31
    Originally posted by Tungsten dipper View Post
    I saw it too. My first thoughts were what is that doing to the precision bearings? How long would they last machining those day after day?

    Could be done on the mill. Maybe twice the time?
    Load ratings on lathe spindle bearings are typically really high for any machining related use. Lathe bearings are selected to get enough high stiffness and large spindle bore. "Side effect" is that the safe load rating is just enormous.
    Location: Helsinki, Finland, Europe

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    • #32
      So here's why I disagree with you fellas claiming this is unsafe.

      Typically, any stock held 1:1 is safe to turn on. Obviously the heavier the item the better it is horizontally. So a 6" diameter part sticking 6" out with a good toothy chuck, no issue. Here he has a greater than 1:1 diameter to stickout. Granted, he only has two jaws in good contact. Also, that gator doesn't have teeth like a Cushman. You'd have to machine grooves in it with the jaw teeth to escape a cushman.

      Additionally, it's a light cut. And he's been doing this type of work for years. Making a blanket statement that this is never safe is BS.
      21" Royersford Excelsior CamelBack Drillpress Restoration
      1943 Sidney 16x54 Lathe Restoration

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      • #33
        Metal Butcher
        Color me dumb, I have worked in machine shops my whole life, but I have no idea what you are talking about ?
        What is 1:1 ?
        What is a Cushman ?
        By "Gator" I assume you mean the chuck he was using ?

        When ever we make "assumptions", we can make mistakes- simple fact of life
        Is it assumed that he will make a light cut ?
        Is it assumed he has done this for years ?
        I didn't watch the video, and looked at the picture, so I am guilty of assuming things as well
        AND the big question !!! was it or is it safe ? .. It may be safe for him, but not for general shop for you or me
        I am reminded of roofers running up and down 20 foot ladders. they consider it safe, but ask the average person (non roofer) if it is safe ..99 % will say no

        Rich

        last word.--anytime you hold a part in a lathe with only 2 jaws and turn on the spindle--You got problems ! -especially with irregular shapes.
        And "safe" does not mean guaranteed personal safety and/or safety of the work piece
        Green Bay, WI

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        • #34
          Originally posted by Rich Carlstedt View Post
          Metal Butcher
          Color me dumb, I have worked in machine shops my whole life, but I have no idea what you are talking about ?
          What is 1:1 ?
          What is a Cushman ?
          By "Gator" I assume you mean the chuck he was using ?

          When ever we make "assumptions", we can make mistakes- simple fact of life
          Is it assumed that he will make a light cut ?
          Is it assumed he has done this for years ?
          I didn't watch the video, and looked at the picture, so I am guilty of assuming things as well
          AND the big question !!! was it or is it safe ? .. It may be safe for him, but not for general shop for you or me
          I am reminded of roofers running up and down 20 foot ladders. they consider it safe, but ask the average person (non roofer) if it is safe ..99 % will say no

          Rich

          last word.--anytime you hold a part in a lathe with only 2 jaws and turn on the spindle--You got problems ! -especially with irregular shapes.
          And "safe" does not mean guaranteed personal safety and/or safety of the work piece
          1:1 stickout. As in length:diameter ratio. And I have seen parts come out at 1:1 plenty of times. Just as important as stickout is the coefficient of friction between the jaws and the part, (in other words, how pointy the jaw teeth are, as well as how tight the chuck is) as well as how much of the part is inside the jaws.

          Cushman is a pretty famous old U.S. high quality chuck and tooling maker.

          Gator is the brand of chuck in the photo - as can be seen by the logo on the chuck face.

          The assumptions are probably (apparently, by the comments) colored by the fact that some of these guys are familiar with the guy in the photos and have apparently seen some of his youtube videos. I myself am unfamiliar.

          I wouldn't say the part was held by 2 jaws, but by 4, albeit a bit precariously on one or more. It would still be wedged in pretty tightly, but any time a jaw is in contact with only a corner, there is the possibility of a little wearing in of the jaw teeth on the part causing things to loosen up. Light cuts are the order of the day in such a case.
          Last edited by eKretz; 05-22-2022, 10:31 AM.

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          • #35
            It was an okay setup for light feeds and speeds. However in the past I have welded on a block of steel where I needed it for a better grip to be removed later. I have also welded on a section of heavy wall tube to one side and chucked the part in the 3 jaw. You make more money in a commercial shop when you leave the 4-jaw to gather dust as much as possible.
            I just need one more tool,just one!

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            • #36
              Originally posted by Rich Carlstedt View Post
              Metal Butcher
              Color me dumb, I have worked in machine shops my whole life, but I have no idea what you are talking about ?
              What is 1:1 ?
              What is a Cushman ?
              By "Gator" I assume you mean the chuck he was using ?

              When ever we make "assumptions", we can make mistakes- simple fact of life
              Is it assumed that he will make a light cut ?
              Is it assumed he has done this for years ?
              I didn't watch the video, and looked at the picture, so I am guilty of assuming things as well
              AND the big question !!! was it or is it safe ? .. It may be safe for him, but not for general shop for you or me
              I am reminded of roofers running up and down 20 foot ladders. they consider it safe, but ask the average person (non roofer) if it is safe ..99 % will say no

              Rich

              last word.--anytime you hold a part in a lathe with only 2 jaws and turn on the spindle--You got problems ! -especially with irregular shapes.
              And "safe" does not mean guaranteed personal safety and/or safety of the work piece
              I have worked in machine shops my whole life
              What is a Cushman ?
              I have been an auto mechanic my whole life. What is a Ford?

              I do not wish for the 99th percentile of humans to tell me how to run a lathe. Hell, I only listen to a small percent of the small percent who do run lathes.

              Lastly, please do a little googling on "2 jaw chuck". You will find that they are specifically designed for holding odd shaped parts.
              21" Royersford Excelsior CamelBack Drillpress Restoration
              1943 Sidney 16x54 Lathe Restoration

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              • #37
                Originally posted by The Metal Butcher View Post
                ......I do not wish for the 99th percentile of humans to tell me how to run a lathe. Hell, I only listen to a small percent of the small percent who do run lathes.
                .........
                yes, that's obvious, point taken

                Rich

                Green Bay, WI

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                • #38
                  Originally posted by eKretz View Post
                  1:1 stickout. As in length:diameter ratio. And I have seen parts come out at 1:1 plenty of times. Just as important as stickout is the coefficient of friction between the jaws and the part, (in other words, how pointy the jaw teeth are, as well as how tight the chuck is) as well as how much of the part is inside the jaws.
                  Cushman is a pretty famous old U.S. high quality chuck and tooling maker.
                  Gator is the brand of chuck in the photo - as can be seen by the logo on the chuck face.
                  The assumptions are probably (apparently, by the comments) colored by the fact that some of these guys are familiar with the guy in the photos and have apparently seen some of his youtube videos. I myself am unfamiliar.
                  I wouldn't say the part was held by 2 jaws, but by 4, albeit a bit precariously on one or more. It would still be wedged in pretty tightly, but any time a jaw is in contact with only a corner, there is the possibility of a little wearing in of the jaw teeth on the part causing things to loosen up. Light cuts are the order of the day in such a case.
                  Thank you for the interpretation -appreciate it
                  Stickout--Never heard that term in our machine shop (s) except it was used in Welding where it was a common term .
                  Yes, I know Cushman, but not Gator
                  I did not say the part had 2 jaw contact , the poster said that ....my reference is 2 jaw is "unsafe"---- at any speed

                  The real question is ( and which will PO the Slam/Bam Thank You Mam ! machinists ) is why he did not reverse the jaws to make it safer ?
                  --- I know why,---it was to make the job go faster, and in my career in shops, we did not do that ...so be it
                  Rich
                  Green Bay, WI

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                  • #39
                    IMO the reason the jaws were's reversed is 1. to stand off the part so it could be faced and bored in one operation and 2. it's a flame-cut part so each jaw would probably be bearing on one small point anyway, plus there's nothing to say that those points will be at the same distance from the rear face. By using the inside steps he's guaranteeing that all of the clamping is on one plane so the part cannot rock itself loose.
                    Peter - novice home machinist, modern motorcycle enthusiast.

                    Denford Viceroy 280 Synchro (11 x 24)
                    Herbert 0V adapted to R8 by 'Sir John'.
                    Monarch 10EE 1942

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                    • #40
                      It's nothing too horrible if you know what you are doing.

                      I don;t know I would recommend it here, just because of new folks who might not be as cautious as they ought to be when taking cuts.

                      He was facing it lightly, and it looked like only doing some minor boring (I did not watch the whole thing). Good enough for that, defintely.
                      CNC machines only go through the motions

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                      • #41
                        Originally posted by winchman View Post
                        Saw this on a machining video. Heavy steel part with lots of stick-out in a big 4-jaw chuck.

                        Is this safe? What would you do differently?

                        It looks safe to me, I have seen some fat chunks in a lathe, it gets scary. This one? Not so much. The mechanic has a firm grip on the part IMO. JR

                        P.S. The larger the piece the easier the cut,, JR

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                        • #42
                          Originally posted by Rich Carlstedt View Post
                          Metal Butcher
                          Color me dumb, I have worked in machine shops my whole life, but I have no idea what you are talking about ?
                          What is 1:1 ?
                          What is a Cushman ?
                          By "Gator" I assume you mean the chuck he was using ?

                          When ever we make "assumptions", we can make mistakes- simple fact of life
                          Is it assumed that he will make a light cut ?
                          Is it assumed he has done this for years ?
                          I didn't watch the video, and looked at the picture, so I am guilty of assuming things as well
                          AND the big question !!! was it or is it safe ? .. It may be safe for him, but not for general shop for you or me
                          I am reminded of roofers running up and down 20 foot ladders. they consider it safe, but ask the average person (non roofer) if it is safe ..99 % will say no

                          Rich

                          last word.--anytime you hold a part in a lathe with only 2 jaws and turn on the spindle--You got problems ! -especially with irregular shapes.
                          And "safe" does not mean guaranteed personal safety and/or safety of the work piece
                          Just because you have a lack of experience in something
                          does not mean it is dangerous for the person doing the job.

                          -D
                          DZER

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                          • #43
                            With a setup like any little hiccup might cause the tool to take a deeper cut. With that much stick-out (the tool is about five inches from the chuck) and that large a radius (at the tip of the odd-shaped piece) the forces might cause it to shift in the jaws, and suddenly the depth of cut is huge, and the piece is spinning around on top of the ways. Since it's spinning counter-clockwise, it will probably move toward the operator. Sure, that's a worst case scenario, but why take a chance when the preventive measures are so simple.

                            I've spent hundreds of hours using a lathe, and I've done lots interrupted cuts on irregular-shaped parts a fraction of the size of that chunk. I've always found a way to ensure the parts weren't going to move, and I've always thought it was time/effort well spent.
                            Any products mentioned in my posts have been endorsed by their manufacturer.

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                            • #44
                              Originally posted by Doozer View Post

                              Just because you have a lack of experience in something
                              does not mean it is dangerous for the person doing the job.

                              -D
                              Oh, but I don't lack experience Doozer , Spent my entire life in the shop and did round dies upto 114 " in diameter and 13,000 pounds and worth $$$$

                              This website is to help less experienced folks, and when you condone risky applications, I find that totally contrary to good machining practices
                              I have known a few wrench jockeys in my life who did stuff like that . but when you risk damaging a part, or a person,--- then it should be called for what it is.
                              If you think my question showed a lack of knowledge, it wasn't--I--t was to explore what a poster meant --which is unlike some posters who attack without
                              knowing the true intent of the comment.

                              Where are you on this ?

                              Rich

                              PS , go read my first post where all I said was----it was not safe !
                              Green Bay, WI

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                              • #45
                                Rich, just as a point of interest, you stated previously that you had not watched the video and only based you thoughts on the content of the photos.
                                Since I do very much respect your experience and opinion, have you since watched the entire video so as to have a better overall feel as to what transpired and thus offer a possibly more informed opinion?
                                Home, down in the valley behind the Red Angus
                                Bad Decisions Make Good Stories​

                                Location: British Columbia

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