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  1. #11
    Quote Originally Posted by Ger21 View Post
    Are you sure you were climb cutting? Climb cutting will push the board away from the tool, not pull it towards it.
    Gerry,

    In my experience climb milling always wants to drag the material, table etc towards the cutter.... get an old milling machine with a bit of backlash, put a decent size cutter in and put a good size cut on. Watch what happens when you try to climb mill... you end up tightening the bed locking screws to stop it from jerking towards the cutter. When toolmaking and using aluminium I always used to rough the sides of plates by conventional milling as you could rip the material off quick but left a rough finish, then leave 0.5mm or so on for climb mill finishing which left a nice smooth finish.

    Nice screenset by the way....



    Click image for larger version. 

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  2. #12
    Ger21's Avatar
    Lives in Detroit, United States. Last Activity: 6 Hours Ago Has been a member for 5-6 years. Has a total post count of 508. Received thanks 68 times, giving thanks to others 0 times. Referred 1 members to the community.
    If there is play in the machine, then climb cutting can cause a sudden jerk, and climb cutting will self feed. However, the cutter is still pushing the work away. Looking at your picture, the cutter enters the work almost perpendicular. The forces are pushing the tool away, but since it has nowhere to go, it appears to grab. If the cutter was actually pulling the work toward it, it would dig in. Instead, it rides along the edge.

    Try this. Program two identically sized squares, and cut one with a conventional cut, and one with a climb cut. The climb cut will always be slightly larger, because the bit is pushing away from the material. With the conventional cut, the bit is pulling into the material, resulting in a smaller part. A lot of shopbot users use this to their advantage when cutting cabinet parts. They do a "rough" climb cut sluightly oversize, then finish with a conventional cut. By removing a very small amount with the conventional cut, it minimizes the effect of the bit being pulled into the parts.

  3. #13
    Quote Originally Posted by Ger21 View Post
    A lot of shopbot users use this to their advantage when cutting cabinet parts. They do a "rough" climb cut sluightly oversize, then finish with a conventional cut. By removing a very small amount with the conventional cut, it minimizes the effect of the bit being pulled into the parts.
    Thats exactly what and why I do it this way, the shop bot forum is where I learnt it also. . . It also removes the burr on end grain nicely.

  4. #14
    Think that we are on a different wavelength slightly, i am not talking about the cutter pushing off as you describe I am trying to say that the effect of climb milling pulls the work towards (or across) the cutter.

    In the 2 sketch's below I have shown worse case scenario....


    The sketch shows the two operators standing next to the machine, Monkey B has bigger balls than Monkey A and decides to stand at the end of the table in the 'danger zone'. Monkey A puts a 4mm cut on a 50mm x 20mm piece of aluminium bar and starts a climb milling cut.

    Click image for larger version. 

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    Monkey A notices the clamps are not very tight but does not stand back or stop the feed, Monkey B can not see this from where he is standing and moves closer to see what the noise is. Job comes loose and gets pushed towards him with enough force to embed the job in his chest. Monkey A has no injuries and calls for an ambulance.

    Click image for larger version. 

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    Monkey C says, "can't believe that we are having a discussion about this"..... Lights up a fag...


    Best get on with some work.....

  5. #15
    Ger21's Avatar
    Lives in Detroit, United States. Last Activity: 6 Hours Ago Has been a member for 5-6 years. Has a total post count of 508. Received thanks 68 times, giving thanks to others 0 times. Referred 1 members to the community.
    Quote Originally Posted by HiltonSteve View Post
    e I am trying to say that the effect of climb milling pulls the work towards (or across) the cutter.
    The word "towards" is the key here. As you clarified, it does not pull the work towards the bit, but rather along it. I was just trying to say that it doesn't pull into the cutter. If the parts were not clamped down, climb cutting would simply push the work away from the bit, and not throw it out the end of the machine. In order to be thrown, it's position must be constrained in the perpendicular direction, so that the cutter can actually grab the workpiece. If not constrained, it won't be thrown, and monkey B's larger balls would remain intact.

    At my day job, we have a large router with two 25HP vacuum pumps to hold sheet goods down. When a part moves a little while climb cutting, it's simply pushed out of the way. If it moves while conventional cutting, the part is pulled into the cutter and typically gets cut in half.

  6. #16
    Quote Originally Posted by Ger21 View Post
    The word "towards" is the key here. As you clarified, it does not pull the work towards the bit, but rather along it. I was just trying to say that it doesn't pull into the cutter. If the parts were not clamped down, climb cutting would simply push the work away from the bit, and not throw it out the end of the machine. In order to be thrown, it's position must be constrained in the perpendicular direction, so that the cutter can actually grab the workpiece. If not constrained, it won't be thrown, and monkey B's larger balls would remain intact.
    .
    Totally agree....

    Thing is, I was Monkey B! the job did not embed itself in my chest just hit me and made me jump. Still bloody hurt but I suppose thats what happens when trying to run 3 machines and answer the phone at the same time..... My mate found it funny though!

    Quote Originally Posted by Ger21 View Post
    At my day job, we have a large router with two 25HP vacuum pumps to hold sheet goods down. When a part moves a little while climb cutting, it's simply pushed out of the way. If it moves while conventional cutting, the part is pulled into the cutter and typically gets cut in half.
    Not enough experience with cutting wood but what your saying does make sense, with steel you tend to clamp things down the best that you can so they dont move at all, if they do move then it starts costing you money!

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