I have a piece of 1/4" steel bar stock that I am trying to make a gib/shim out of.
As it is .. its too wide. To try and get it narrower .. I tried to mill
the edge with a 2f endmill. I have a set of endmill holders coming ... but for right
now ... I again tried to use the damn drill chuck .. lol .. and it again .. came apart.
But before it came apart, I had trouble keeping the endmill on the edge of the bar stock.
it would wonder off. And it really chattered . Was this because I used the drill
chuck .. or .. because you just don't do what I was trying to do .. or .. because
my machine just isn't ridged enough to do this ?
There's no delicate way to say it. Wise people don't use a drill chuck to mill. Not for any reason.
If you continue the practice, you're most likely to discover that the chuck will not stay on the shank, so you'll have to replace both of them.
Don't remove material from only one side when machining bar stock---especially cold rolled materials. Internal stresses will cause the part to bow, with the convex surface being the side machined. Take small and equal cuts from both faces, alternately, to help keep the piece straight.
The end mill wandered off? Which way? If the cut became shallow, as if the end mill was pushing away from the cut, I'd suggest that the chatter you mentioned was allowing the screw to back off. That's what table (and saddle) locks are for. They prevent that from happening.
Why the chatter?
Hard to say. Could be the machine simply isn't rigid enough to machine steel without issues---but not using a drill chuck, alone, will make a huge difference. The closer to the bottom bearing of the spindle you can hold a cutting tool, the greater will be the rigidity of the setup. Simply hanging a cutter from the drill chuck is more than reason enough to have the problems you're experiencing. I'd even suggest you not use end mill adapters---collets hold things much closer to the bearing, and are, as a result, far more rigid.
It's simple. Be patient, and lose the idea that you can mill with a drill chuck. That, to me, is driving in to the garage by driving through the closed door. Not exactly how it's supposed to be used.