What is CRS? I have to check my fly cutter often to insure it hasn't slipped. I never considered putting something soft between the screw & tool. However I do realize that it is slipping because the screws are hard & so is the tool.
Another thing to watch out for is something that happened to me the other day. I'm not sure what happened but I crashed my mill. I was cleaning up the last side on a piece when the work was pulled up out of my vise, sheared the pin that aligns the R8 collet, & my fly cutter was bent. It did stall the motor but not fast enough. I did have 2/3 of the work above the vice so I don't know if this is what caused it out not.
CRS = Cold Rolled Steel
The crash can be caused by a number of things. Having the work pulled up is more common to end mills than fly cutters.
There are two basic causes of this sort of thing. Tool rake or pressure causing something to move, and loose machine parts.
I will hazard that you had one of two things go wrong. Either the work was not properly clamped, or the x-axis gib was loose enough to allow the table to tip as the center of balance went over center. Another possibility is the z-axis slid down from machine vibration. Always lock all unused axes.
Some general rules for vises:
Paper shims increase friction a lot, use them when needed.
Only place flat machined surfaces against the fixed jaw. You can break this rule a lot. Mill scale can damaged the jaw over time. Small irregularities will cause the vise to not clamp properly. Always check the surface for dings, high spots, and the like. Flatten with a file if needed. I usually put a piece of paper between hot rolled and the jaw to help gripping power and compensate for the irregular surface.
Only clamp parallel faces between the jaws. This one should be violated only at your own risk. Until this face is machined flat and parallel, a piece of soft metal such as heavy copper wire, or aluminum should be put between the moving jaw and the work. This will ensure the fixed jaw is the reference and compensate for irregular and out of parallel surfaces. Some stock comes pretty parallel, you can use paper on both sides. I use 10ga wire scraps. You can by some at the hardware store in the electrical department. Just buy what ever is cheap in 10ga or 12ga wire.
Only clamp in the center of the vise. Use a spacer or jack on the other side of the jaw if yo need to use just one side of the jaw. You can wrack a vise easily by using only one side of the jaw.
Curved surfaces need to be clamped using v-blocks.
Keep stick out to a minimum. To much stick out will cause vibration, vibration can cause the work to come loose.
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