Announcement

Collapse
No announcement yet.

Grinding Something Longer Than The Chuck

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Grinding Something Longer Than The Chuck

    I've welded up all the nicks and dings in the top edge of my finger brake apron. I would like to finish cleaning it up on my grinder. My chuck is 18" long and the apron is 28" long. It has to set on the ends as shown in the picture. The center of the bottom edge of the apron is slightly convex so if I grind 18" of it and slide it forward on the chuck it will start to drop off and I won't get a straight cut.

    I've done this before with longer parts with good results but since the bottom edge of this is not dead flat I know what is going to happen.

    I don't have a long reference bar that I could clamp to the apron to act as a guide and I won't even attempt to try and shim it as I go. Thought or ideas ??

    JL...............

    Click image for larger version  Name:	IMG-20201117-103625.jpg Views:	0 Size:	295.7 KB ID:	1910918

    Click image for larger version  Name:	IMG-20201117-103644.jpg Views:	0 Size:	143.2 KB ID:	1910919

  • #2
    Anyway to get the bottom flat enough to do the slide technique? It wouldn’t have to be the whole bottom, seems like a point on each end and one in the middle would do it. Even if that meant having to weld something on temporary for the 3 points.

    Comment


    • #3
      How straight is the working edge at this point?

      I'm thinking dress off any raised burrs that you're intending to remove mostly with a stone or by peening the material back down into the edge to make it reasonably flat and straight. Then using that as your reference edge grind the opposing edge flat and parallel to the working edge and then flip it around and do the dressing off of the intended edge.

      If it's curved by a fair amount you could rough the worst of it away with files or angle grinders after marking off.
      Chilliwack BC, Canada

      Comment


      • #4
        Would using a cup wheel provide any advantage in being able to mag it down on the flat edge ?

        -D
        DZER

        Comment


        • #5
          Originally posted by Doozer View Post
          Would using a cup wheel provide any advantage in being able to mag it down on the flat edge ?

          -D
          If alignment posts could be then set against the newly cleaned up edge at the far end and middle of the new edge then the rest could be advanced and done in short bites using the posts referencing off the already ground part.
          Chilliwack BC, Canada

          Comment


          • #6
            You really need a reference surface.

            You are saying you do not have one, and can't make one, plus do not want to do shims. At that point you would be stuck, wouldn't you?

            Is your table flat if you remove the chuck for this job?

            What is the total travel of the grinder?

            Seems like you are going to need to set up the posts/raising blocks/whatever. And probably you will need to shim it.

            Making the bottom flat seems like the obvious other answer.... and it will have benefits later if you need to do this again.

            So which is giving way? The rock, or the hard place? The irresistible force or the immovable object?
            1601 2137 5683 1002 1437

            Keep eye on ball.
            Hashim Khan

            If you look closely at a digital signal, you find out it is really analog......

            Comment


            • #7
              Originally posted by oxford View Post
              Anyway to get the bottom flat enough to do the slide technique? It wouldn’t have to be the whole bottom, seems like a point on each end and one in the middle would do it. Even if that meant having to weld something on temporary for the 3 points.
              I had thought about milling the bottom edge to get the dip out of it but I'm running into the same issue as the grinder. I don't have enough travel in the mill. The table is 42" long. I would still have to slide the apron forward after running out of travel and move the table back to finish up.
              I don't know what error I would run into doing this.

              JL................

              Comment


              • #8
                Originally posted by Doozer View Post
                Would using a cup wheel provide any advantage in being able to mag it down on the flat edge ?

                -D
                I wouldn't be able to fixture it up that way. The apron is 6" wide and so is my magnetic chuck. Plus I would still run into the issue of no guide edge to slide it along.

                I can't put the cup wheel on with the cutting edge facing into the machine, which means the apron would be hanging off the front and of the chuck.
                Further...... If I were to do it this way I wouldn't really need a cup wheel. I could go off the edge of the grinding wheel. Don't like it, but I've used it that way in a pinch for small things.

                JL................
                Last edited by JoeLee; 11-17-2020, 03:49 PM.

                Comment


                • #9
                  Just scrape the bottom flat, then scrape the top flat.

                  Comment


                  • #10
                    Originally posted by J Tiers View Post
                    You really need a reference surface.

                    You are saying you do not have one, and can't make one, plus do not want to do shims. At that point you would be stuck, wouldn't you?

                    Is your table flat if you remove the chuck for this job?

                    What is the total travel of the grinder?

                    Seems like you are going to need to set up the posts/raising blocks/whatever. And probably you will need to shim it.

                    Making the bottom flat seems like the obvious other answer.... and it will have benefits later if you need to do this again.

                    So which is giving way? The rock, or the hard place? The irresistible force or the immovable object?
                    That pretty much sums it up.
                    The raised area of the table where the chuck mounts isn't much longer than the 18" chuck, maybe an inch or so on each end. Total travel of the grinder is 18" + a little over travel.
                    If I had a 30" ref. bar I could set both up on the surface plate, clamp the apron to the bar and transfer it to the grinder.

                    I have a lot of pieces CF bar in all different sizes but none are straight enough to use as a ref. bar.

                    I've done the slide method with the blades off my 24" shear but they were dead straight. I'm almost tempted to take the blades off the shear and clamp them to the apron as a reference bar.
                    That might be my only way out.

                    JL..............

                    Comment


                    • #11
                      Originally posted by JoeLee View Post
                      ... I could go off the edge of the grinding wheel. Don't like it, but I've used it that way in a pinch for small things.

                      JL................
                      Side wheeling is kinda dangerous.
                      At the very least, back relieve the contact area
                      of the side face so only a thin line (1/4" or less)
                      is actually cutting. Else you will generate so much
                      heat, you could crack a wheel. Bad thing.

                      --Doozer
                      DZER

                      Comment


                      • #12
                        Could you clamp it to angle plates, grind a bit, move it over, indicate on the ground edge and grind a little more? Chance for errors to stack up and you need to get it clamped correctly for the first grind.

                        Agree with Doozer about side wheeling. It also is very slow going – you can't take much of a cut.
                        George
                        Traverse City, MI

                        Comment


                        • #13
                          I would just set it up on the mill, with both ends on the mill table. Mill the edge with an end mill. It will be plenty straight.
                          Kansas City area

                          Comment


                          • #14
                            Take 3 blocks and grind the bottoms flat, they only have to be an inch or two wide.

                            Set the shear bed on your surface plate, mill table, or whatever the flattest table/spot you have.

                            Get the top of the shear bed indicated out to where it needs to be to get ground with shims underneath just enough to have the whole be floating and resting on the shims

                            Take the 3 blocks with the flat bottom and tack/weld them to the bed. You should only need 3 if you can do entire part in 1 move, 4 if you need to move it twice.

                            Angle plate on the grinder chuck to clamp to it and grind away.

                            Comment


                            • #15
                              Originally posted by George Bulliss View Post
                              Could you clamp it to angle plates, grind a bit, move it over, indicate on the ground edge and grind a little more? Chance for errors to stack up and you need to get it clamped correctly for the first grind.

                              Agree with Doozer about side wheeling. It also is very slow going – you can't take much of a cut.
                              Possibly, but the angle plates would have to be positioned close to each end of the apron or I won't be able to reach them with clamps.

                              I know grinding off the side of a wheel is not the smartest thing to do.

                              JL...............

                              Comment

                              Working...
                              X