thanks jmb,you have just clarified my actions,i have found that hire sanders arent up to much cop,so i returned to my 4 in makita previous to getting my ro 150,allthough i remeber having to go back with a finer grit because it left scratches,made by either the rotary motion or the eccentric motion with the ro 150,and as i am sanding down a pre finshed engineered floor as apposed to an unfinished oak floor,which grit would yo finish with?
Oh I c. Yeah the floors I have layed where unfinished as of course the finished ones wouldnt need sanding. Well I have always used a 80 grit in geared mode to go round quickly to remove the filler and anything else and get it all smooth and and flat. Then go round again with 80 in fine mode. Then I finish it of with a 120grit
but a worn 80 grit in fine mode does a smooth enough job for flooring and I find that its often enough so you dont need to use 120grit well thats me any way. What you going to use as a finish? Osmo? I like Osmo nice stuff.
Im going back to a job on the 14 feb fit some oak stairs and I layed his oak flooring so ill have a look at what it looks like as his flooring was an unfinished floor and needed sanding and I only used a 80grit for the entire floor in geared then fine mode. He wanted to stain the floor to save money so I recommend him to buy OSMO so I never got to see it finished.
I might take some pictures if it looks good

It must as he wants me back to do more work and wants me to do some more oak flooring in some other rooms.
JMB