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Thread: What Damage Might I Have Caused?

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    Default What Damage Might I Have Caused?

    Hi Folks,

    So I have aquired a 3600 pound CNC knee mill, brand new. It's got Meehanite castings and a 11" x 58" table. I was thinking of making a stand for it, so I purchased some 5" wide C-channel, about 35" in length (25" for the width of the mill, plus 5" on each side). I bought 2 sections of C-channel, one to go across the width of the front of the mill and the other to go across the back.

    I needed to mark the holes where I would drill the channel, to bolt it to the mill. Using my company's forklift, I lifted the mill from the side with the forks under the ram, on both sides of the column. I used about 2" of plywood between the forks and the ram, and I made sure the ram and turret were locked down. Due to the fact that my forklift only has 4ft forks, I had to move the table away from the side I was lifting from. This caused the mill to tilt as I was lifting it, and it made it extremely difficult to get the C-channel lined up correctly.

    What I tried, at one point, was to set the mill on the C-channel, both front and rear, and attempt to hammer the channel into alignment (with a handheld 3 to 5 lb sledge), while taking a bit of weight off with the forklift. This absolutely did not work and the channel was not moving whatsoever. In the end, I did get everything lined up and my holes marked, simply by moving the channel and setting the mill down (this took some luck, as the mill was tilted heavily while in the air).

    When I removed the channel and set the mill down, I noticed that the ram was no longer square over the table. It seems that by me beating on the C-channel, I had actually moved the base about 5 degrees out of square. Of course I know that the ram/turret can move this way, but I can't imagine it did it any good moving while the turret was tightened.

    Now, I am concerned that I may have caused a crack somewhere (given cast iron's low tensile and impact strength).

    How concerned should I be? Working with cast iron of this size is new to me.

    Pretty stupid of me, I know.

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    Default Re: What Damage Might I Have Caused?

    all that means is the bolts holding the turret weren't tight.

    if they were tight it would take thousands of foot pounds of torque to cause that joint to slip (assuming its on the order of 16" diameter and you've got 4, half inch bolts torqued to >20 foot pounds)



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    Default Re: What Damage Might I Have Caused?

    Quote Originally Posted by Eldon_Joh View Post
    all that means is the bolts holding the turret weren't tight.

    if they were tight it would take thousands of foot pounds of torque to cause that joint to slip (assuming its on the order of 16" diameter and you've got 4, half inch bolts torqued to >20 foot pounds)
    Thanks for your reply.

    My real concern, however, is could my beating on the C-channel have caused any cracks?

    I am pretty sure that the 4 turret bolts had >20 ft/lbs of torque on them.

    I also know that impact from even a small hammer can put forth tremendous amounts of pressure.

    However, please keep in mind that nothing was positively locked to each other (as in bolted, except for the turret).

    The C-channel was just sitting underneath the mill, the ram was just sitting on the wood, the wood was just sitting on the lift truck's forks, etc. There were many opportunities for things to move as I was hitting the C-channel.

    I'm just concerned about the strength of the cast iron, and there is no reasonable way I could check everything for cracks.

    It's really bugging me.



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    Default Re: What Damage Might I Have Caused?

    the most force you could apply to the machine is the friction coefficient multiplied by the weight, i would not be worried about it.



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    Default Re: What Damage Might I Have Caused?

    Quote Originally Posted by Eldon_Joh View Post
    the most force you could apply to the machine is the friction coefficient multiplied by the weight, i would not be worried about it.
    Thank you for helping ease my fears. I've searched this forum and PM, and I could not find anyone who has caused a crack in their mill (short of dropping it or a terrible crash). I would hate to be the first.



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