I'll take a stab, I've had a few floppy CNC machines, still have one, a 2hp and a 5hp, both quill style machines. I still have one, A wells index 847.
No idea what your machine is but.... First off, generally an indexable mill using inserts is going to eat up more HP than an endmill, generally(not always), based on geometry and how free cutting they are.
The video you saw (you may not have heard all the audio) had a 1/2 D stepover, what you are trying to do is basically a full slot. What I've learned to get the most out of a floppy machine and use all its HP is you have to twist the machine up, sounds horrible, but it works.
In other words, its going to flex, all machines do, some more than others, so, the trick is to get it to flex in one direction until its all twisted up and keep it there. When slotting, or running full D the cutter is pushing and pulling in a bunch of different directions which can make for some nasty milling, lots of chatter and chipped cutters. Ramping while making a full width cut can sometimes help that by pushing the head up, or running not so deep and feeding like crazy to try and keep the majority of your forces pushing back towards were you came from.
On a profile cut, run it as deep as you can and increase your feed and stepover until you run out of HP or break your cutter, keeps the machine twisted up sideways.
As for endmills/inserted mills, he might be doing something you don't see. Variable helix/flute endmills can really make a floppy machine shine, I've actually several times started a job that chattered like hell, and all of a sudden was cutting nice and quiet, check the endmill and one flute was broken off, these were variable flute endmills, and they cut better and quieter on the floppy machine with only 3 flutes, apparently 87,93,180 degrees really broke up the harmonics. Maye he has one insert with a different geometry or nose radius or maybe one is just trashed and not doing anything.
Maybe you're not feeding hard enough, first thing I do when I hear a squeel is feed her harder. If its on a finish pass, I'll leave more stock or sometimes on a finish with a long endmill If I leave it a little to chew on on the bottom, say full width for .015 of depth or so, the cutter will stabilize and do its thing nicely.
Could be a million things, ways, bearings, backlash, bad belts to the spindle, tool retention(<--- this is HUGE!!!!!), tool length, tool holder itself, tool taper. That one grey beard hair that you refused to acknowledge the existence of is on the taper of your collet or tool holder and screwing everything up.
Could be a million things, just need to go at it systematically and don't be afraid to play around and try new tools and techniques.
I'd start with condition of the machine and tool retention before I started dumping money on tools hoping to find the magic cure all.  | 
09-08-2009, 05:55 PM
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