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striaghtening bent shafts

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  • striaghtening bent shafts

    I often hear of machinists striaghtening bent shafts. Can someone tell me where to look for how-to information? Thanks Paul

  • #2
    Good solid vee blocks, dial indicator, and a press. Mark the high spot(s) and go to it. Press, measure,press, measure,press, measure,press, measure, till straight.

    [This message has been edited by bernie (edited 08-17-2004).]

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    • #3
      Customers come to me all the time for this,I tell them price increases exponitialy according to the level of straightness desired
      I just need one more tool,just one!

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      • #4
        One thing: Never put cast iron under a press either as work or blocking - especially V blocks.

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        • #5
          I made a set of vee blocks from cast iron in school. Are all vee blocks made from cast iron? Yes, I do know not to use them in a press as I heard they could blow apart.

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          • #6
            Method depends on the diameter of the "shaft" i posted a method for straightening a shaft up to about 1/8" on the Tips posting. I have used my method for shafts up to 1/4"diameter, but it gets more difficult or imposible to use my method on shafting much more than 1/8".
            Matt

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            • #7
              I wouldn`t be keen on useing v blocks. My preference would be timber supports at either end and timber between the work and ram, it`s a lot more forgiving. I would determine the runout using the v blocks though. I`ve seen some good machine shop v blocks stuffed by missuse, they have a lovely habit of splitting in two when stressed.

              Ken NZ
              Ken.

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              • #8
                I used one of my sets of vblocks in my 20 ton press to support the ends of a shaft I was straighting, the shaft made a small depresion in each block. Next time I will use scrap to support the workpiece.

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                • #9
                  depending on the kind of shaft. a torch in the right hands can do a excellent job also.

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                  • #10
                    Shine that torch here or turn the damn lights on. I can`t see!
                    Ken.

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                    • #11
                      When I was a kid working in a Harley Davidson shop in the '60's my boss used to straighten bend fork tubes from wrecked Harleys and also for the other dealers in town. He used 3 aluminum radius blocks with a semicircle the same radius as the tube. One under each side of the bend and one between the ram and the tube. A dial indicator to find the high spot as mentioned before. An additional challenge, sometimes the tubes would be out of round. Pinched between two radius blocks in a press he could get them within a few thou' of round.

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                      • #12
                        I had a good friend in the farm irrigation well business that converted an old l2 foot lathe bed into a well shaft-straitening jig. I say a jig; all he did with it was mount three sets of roller bearings (two to the set, across from each other to form a vee so the shaft had a trough to roll in) perfectly in line to the lathe bed. He made another bar the length of the bed that hinged down onto the shaft to be worked on; the bar had three evenly spaced dial indicators mounted on it. He would place the bend shaft on the bearings pull down the dial indicator bar, contact the indicators, rotate the shaft by hand to find the high spots. He would then get the torch out heat and cool with water to draw the shaft back straight. I have seen him straighten some pretty bad stuff this way; he would shoot for a five thousand tolerance. My friend has since passed away; I just wished I had spent more time in the well shop with him. He could find a way to do just about anything with his old mill and lathe; he was strictly a self-taught machinist.

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                        • #13
                          This is a slight variation on shaft straigtening but closly related.

                          I worked at the Colt Factory (as a contractor) in Hartford where they were making M-16's for Viet Nam. At the end of the barrel boring machines was a guy with 2 V-blocks, dial indicator and an arbor press.

                          He would spin the barrel, pull the press lever, spin again as a final check, and out it would go. He could do it in less time than me describing it!!

                          Pete

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                          • #14
                            A few years ago there was a humourously written account of life as an apprentice with Rolls-Royce.

                            It appeared in the Rolls-Royce Heritage Trust magazine "Archive" No.56, written by Michael Forrest and entitled "Henry's Brats-A worms-eye view".

                            The author recounts his experiences in different departments. Here was his account of straightening bent things...

                            "Another Henry never talked to anyone. Never looked at anyone. Followed same footsteps and rigid schedule to seconds. Had huge hydraulic press and big pile of curly camshafts. Spun between centres. Noted random corkscrew effect. Computed in micro-seconds. Stuck under press, two or three squirts. Not a flicker on dial-gauge anywhere. Dead straight. Dominance of jet engine not due to inherent superiority. Harry retired and Rolls-Royce could not straighten camshafts. Harry first industrial robot?

                            In a quiet corner lived the Stretchers. Portly old men, thin grey Brylcreemed hair, smoked pipes. Feet hurt. Sit around biggest marking-out table in world. 'Stretching' Rolls-Royce speak for straighten. Straighten bits bent machining or heat treatment. Pick up, examine. Bong, bong. Straight. Simple. Idiot apprentice. Boing, boing.Worse. BOING, BOING. Like roller coster. Old fogey gives gentle tap, springs flat. Just what I was going to do before he interfered."

                            [This message has been edited by Peter S (edited 08-21-2004).]

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                            • #15
                              When I was in engineering school the white haired manager of the engineering shops mentioned once that he had worked with a big lathe at Mare Island ship yard to straighten a propellor shaft from an aircraft carrier. He said the lathe was big enough to support the big shaft between centers and that they used a bridge crane to pull up on the shaft after heating it with a lot of big torches. He told me the story after I asked where he got some hula hoop sized chips that were leaning against the wall of the school shop.

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