[How do I?] Mill From The Top Or The Side?

The piece is was milling was clamped in 2 , 8 inch vises . Once the backlash is taken up their isn't any movement. This mill weighs over4500 lbs. it came with built in power feeds, not boxes and cords hung on the ends.
I still don't understand how. 1 in cutter puts more pressure than a 3/8 cutter, only milling something 3/8ths wide. Would probably leave a burr on both sides then have to make 2 passes instead of one?
Thanks ron
 
I would have to think through the physics of that to give a reasonable explanation, but I have to say there is a huge difference in running a 1 inch cutter and a 3/8 cutter on my machine, 3500 lbs, zero lash ball screws, and it's tight. Under similar conditions, the larger will bounce the machine around a bit.

If I were going to make that cut, as you suggest, I would make two passes, one down each side. I would also climb cut, but without ball screws I don't think you can do that. Pretty much eliminates the burr if the cutter is sharp.

I think the better way to make your cut is to put the angle in the vices leg down, and use the side of the of the cutter on the leg you want to trim. This is where a rougher would work really well.

I'm about to have a similar discussion with one of my customers. He thinks he is going to cut a 3.75 deep notch out of 4x4x0.25 aluminum angle with the leg sticking up. That is going to require a 1/2 inch end mill with a 4 in DOC, on a nearly unsupported angle. :confused 3: Even at 16K rpm and small bites it ain't gonna happen.;)
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I 100% agree, I can't explain it either, but my machine is not nearly rigid enough to run a 1 inch cutter without deflection.
Think of this, I run an 1/8th inch cutter and you can see it Bend while making the cut when I'm running too hard, the machine don't move, BUT, the same idea applies when using a large diameter, super stout non bending em, the machine WILL deflect unless your running maybe a 20klb big boy, what's why there is such thing as a spring (deflection)pass
 
Wait, I think I can explain it, think of a big mud tire, the surface contact with the ground is substantially more than a donut spare, the big mud Tire being the 1 inch, donut the 3/8, it comes down to surface contact I believe
 
When the cutter is much larger than the with of the surface it is cutting the flutes are hitting across the narrow with thus causing the hammering effect that the op had. With a 3/8 end mill the force is in the length witch will be more ridged. At least that is the way I see it in my experience.
 
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