I apologize to all who are sick of the Domino threads, but I need a little help sorting this out. I received my Domino in early April like many of you, but I really haven't had a chance to use it (other than the obligatory trial mortises I cut when I first received it). I started a project to build a stereo cabinet this weekend and I was looking forward to using the Domino for most of the joinery. However, I can't seem to cut a clean mortise. I tried cutting 5 mm thick mortises at the standard width - no problem. I then tried cutting at the +6 mm width setting. The Domino chattered quite a bit and the mortises were not as clean. At the +10 mm width setting the tool chattered so much that I ended up with "S" shaped mortises or mortises that were of uneven depth. In fact the chatter was so violent that it broke the tip of the cutter.
I tried the 6 mm cutter and the got similar results. I call Festool and talked to a tech who suggested that the problem is most likely technique and less likely a malfunction of the tool. I can accept that for now because I was able to get clean mortises when I played with the 8 mm bit and a very slow plunge rate (much slower than I would normally use for my PC biscuit joiner). So here's my question - what's the best techniques for getting a clean mortise regardless of depth and width?
Thanks in advance for your suggestions.