please help me! been sanding floors for about ten years, always used clarke american 8" drum. never had problems with getting floor flat. i'm actually a little cocky because i take pride in what i do and do it well. started my own buisness 2 years ago and purchased bran new clarke drum. seemed to run fine with no problems until past couple months where i have noticed chatter that resembles waves 1 " apart. some jobs are worse than otheres but i usually see them everywhere. happened all of a sudden and cannot explain. replaced everything that could cause it and did not change so clarke gave me a bran new machine. just used it and it seemed to be running great but when i applied first coat i noticed in a few spots some chatter or now i think maybe dish out because of the open grain of the oak. never had this problem and i work by word of mouth so if anyone can help me get to the bottom of this i would appreciate it. never changed sanding routine or anything. here is waht i have done for 10 years, problem free.
rough pass- 36 for stain- 36, 80, 100 then buff 150
fine pass- 80
buff- 120

I suggest you join the floormasters forum and browse around there. It is just for professional floor finishers and installers. We talk about this subject and all subjects related to installing, sanding and finishing wood floors. Some manufacturer's reps post occassionally from Clarke, Dura Seal, and more. Very educational. Many experienced pros who post. The site is hosted by Bill Price, a nationally renowned flooring professional and educator. Here's the address: http://www.floormasters.com/