I am trying to do a run of several parts and cut down on operations. I have it down to 2 right now but I am getting some chatter and I am wondering if it is due to my workholding setup.

My first operation is just milling out 2 countersunk holes in a vise. For the second operation, I have an aluminum jig with two steel dowels in it that fit into the countersink and through holes made in the first op. the dowels are threaded 1/4-20 on both ends and I just tighten a nut down on either side. The second op itself consists of milling another countersunk hole and then running a profile around the entire piece. This is on a mini mill so I am running a 3/8 cutter at maybe 2k RPM taking .05 cuts at around 6-7 IPM. Here are a few pictures of the setup - is this setup OK or should I do it differently?







This is what the final piece looks like:


thanks,
Kevin