Quote Originally Posted by cobrakai View Post
Anyone have insight as to what causes this?
This looks like a fairly bad case of what was discussed in this thread:
http://www.cnczone.com/forums/tormac...ml#post1140470
At the end of this post I described a simple calculation that should help you determine whether my assumption is indeed correct. If you can't follow my description simply post your feed rate and spindle speed and I'll calculate the number of "ripples" per inch that expect you're seeing.
Step

Edit:
This the kind of finish that you can (sometimes) get after balancing:
Attachment 253564