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How do you keep work from tipping in a vise?

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  • How do you keep work from tipping in a vise?

    I have a part I need to machine and I have been putting it off because I don't want to ruin it and have to start over. A problem I have many times is if I have a part that needs to be held in the vise jaws above the base of the vise, when I make cuts the part inevitably ends up tilting and then the cuts are at an angle. I have put parallels under the part, and this seems to help a little, but not prevent it 100%. When using the shaper it is really a problem because the shaper will lift the end of the part nearest the shaper out of the vise, not just force the farthest end down.

    The part I have been putting off is a rectangle about 2" long and 1" wide with a 1/2" OD shaft sticking 1" out of the bottom. I need to cut an arc out of it so it looks like an upside-down arch. I am planning on using a 2.5" cutter in my horizontal mill and I am unsure if I should set the cutter depth and run the piece into it horizontally (the cutter can be used as a facing cutter or plunge cutter), or align the cutter over the piece and move the knee up into the cutter vertically. And any tips for clamping the part?

    I'll snap a photo of the part and cutter a little later this evening (I have to finish some firewood stacking before dark).

    Thanks,

    andy b.
    The danger is not that computers will come to think like men - but that men will come to think like computers. - some guy on another forum not dedicated to machining

  • #2
    If I am understanding correctly, the part is lifting slightly off the parallels? If you tap it down with a soft-faced hammer as you tighten the vice you can keep it level.

    I was just watching MIT tech TV and they showed that: http://techtv.mit.edu/search?q=machine+shop&x=0&y=0

    I think it is in part 6.

    -Pete
    I just like to make stuff.

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    • #3
      One question may be, do you have a good-quality vise?

      If you do, and you're having the problem, one option might be to make a set of soft jaws for your vise from aluminum and machine a step/groove to hold the part.
      ----------
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      • #4
        As I understand your question, the part moves in the vise due to cutting forces. I've found placing paper between the work and the part helps by increasing the friction coefficient.

        John

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        • #5
          Part of the problem may be that you are using the wrong tool for the job.

          A 1" wide part is not really going to have all that much gripping area in the vise jaws if you are clamping along the 2" length, given clearance for the jaws from the cutter.

          Better to chuck it up in the 4-jaw on the lathe and use a boring bar to make the cut.

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          • #6
            Better info if you post a picture or complete description. But things I've used to prevent "tipping" include v-blocks, v-notch jaws, and soft jaws cut to "nest" the part (sometimes just convenient scrap dropped/clamped in, not really "jaws"). Likely not to work for you, but on one "job" I welded the piece to be machined onto a piece of scrap tubing so that I could hold it, then cut it loose when done.
            Russ
            Master Floor Sweeper

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            • #7
              You guys have given me some good ideas. I will post a photo in a bit and I'll post one of the part in a vise for an idea I think might work.

              andy b.
              The danger is not that computers will come to think like men - but that men will come to think like computers. - some guy on another forum not dedicated to machining

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              • #8
                Post a photo, I am interested

                Thanks,
                CCBW, MAH

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                • #9
                  Sounds like you may be taking too deep of cuts, or not clamping the part enough. If you clamp it with aluminum jaws, it will tend to not mar the part even with high clamping pressures. Also good vises tend to have hardened and ground smooth jaws that tend not to mar flat surfaces.
                  Also if held on one side of the vise, you need an EQUAL lenth peice of scrap to hold in the other side of your vise or you won't get nearly as much clamping force.

                  Of course, excessive clamping force can also distort a part, to where your cuts may be accurate, but the part changes shape when removed from the vise, But somehow that seems much less disaterous then the part lifting midcut.
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                  • #10
                    First, you should be using a milling vice or a toolmaker's vice. These are designed to minimize jaw lift/tilt.

                    If you have an import milling vice, this photo essay on rebuilding one shows that some makers either don't understand the function of the wedge that pulls the jaw down, or just don't care:
                    http://www.docsmachine.com/projects/4vise/4vise-01.html
                    It is about the third picture in.

                    Even with a good vice, you may need to hammer the work down while tightening as shown in the MIT video.

                    There are also some wedges that can go between the vice jaw and the work, kinda like a tilted knife blade, that push the work down when you tighten.

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                    • #11
                      Well, my digital camera decided tonight was the night to die, so no photos until tomorrow when I go out to Best Buy and do my part for the Christmas economy.
                      I am using an old Bridgeport milling machine vise or the REAL old shaper vise for these projects. On the shaper vise, I can put a 3' pipe extension on the vise handle and hang off of it to tighten the vise and work still moves. I don't take real deep cuts either because I am still a newbie and I'll admit it, I am ascared of things breaking and flinging shards of metal into my body.

                      More to follow tomorrow after my spending spree.......

                      andy b.
                      The danger is not that computers will come to think like men - but that men will come to think like computers. - some guy on another forum not dedicated to machining

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                      • #12
                        Originally posted by andy_b
                        I don't take real deep cuts either because I am still a newbie and I'll admit it, I am ascared of things breaking and flinging shards of metal into my body.
                        Wait till you start feeling like your just getting a handle on it, then bury a brand new 1/2" solid carbide roughing mill in some tough material and forget to lock the knee. It actually lifted the knee, scrapped the part, and broke a ~$30 cutter. It all happened so fast it was over before I realized it was happening, scared the wee outa me. I would never have thought it would LIFT the knee!
                        Russ
                        Master Floor Sweeper

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                        • #13
                          Usually work moves because it is not parrallel to the jaws somewhere along the line.

                          When making heavy cuts, with smooth hard jaws, it is almost impossible to keep work tight.
                          In that case, do the following. Take two strips of 400 wet/dry sandpaper about 2 inches wide and as long as your work, and fold it in half at the 1 inch mark, so the abrasive is on the outside, and clamp between the part and the jaws.
                          It will not hurt either part or vise.
                          If your part has a mirror surface you are afraid of damaging it, put the paper side against the piece ( fold opposite )

                          On Castings, which can be a devil to hold, use 220 emery cloth

                          If you do not like any of the above, then go pour some sheet lead, about 1/8" tp 1/4 thick and use it. Works good

                          Rich

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                          • #14
                            It's probably a good idea where possible to use a machinist's jack to support work that extends beyond the vise. http://www.davehylands.com/Machinist...achinist-Jack/
                            I've often wondered how effective sine plates are for not slipping. http://www.wttool.com/product-exec/p...m_source=froog

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                            • #15
                              Originally posted by Rich Carlstedt

                              When making heavy cuts, with smooth hard jaws, it is almost impossible to keep work tight.
                              Yup, been there. With a new Kurt vise and hard smooth jaws and a hard smooth piece of stock. Had some slipping issues. I didnt use abrasive paper, though that will work.

                              I didnt want to add much thickness to the works so I smeared some very fine lapping compound on the jaws, just a super thin smearing with my finger, so you really couldnt even see it, and clamped her down tight. That helped for me. It added enough friction that I needed due to the very smooth, hard surfaces. JR
                              My old yahoo group. Bridgeport Mill Group

                              https://groups.yahoo.com/neo/groups/...port_mill/info

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