I'm seeing more and more sanding lines in my floors.They can be buffed out,but it takes forever,and dark floors aren't as dark as they should be after all the screening.On oak,pine floors,anyone know a quick way to knock those lines down??I'm also seeing small waves in finished floors,only visible in the correct lighting,approx. 3 to 4" across.Wheels are in good shape,machine runs smooth,no vibration.???
Any tips are appreciated.

The sanding lines can come from hitting staple leg nailhead and the like, it can also be caused by jumping too many grits on the sander. You can try one grit finer, or one more in between and make sure to set any mertal you hit as soon as you hit it or it will repeat throughout the floor, you can also make sure the drum and roller are not leaving any thing in sandpaper, they need to be cleaned well.

dont skip more than one grit. if you are starting out with 40 then you cant jump to 100. 100 will take out a 60 scratch but a 40 will have to be buffed for too long. Do you run a hummel by chance? waves can be caused by a lot of diffrent things, there is a ton of debate over what the root. for starters i think its a drum pressure spring complicated by the diffrence in density between the hard and soft grain of the floor. It tends to show up more when the butt joints in the floor are high and the hummel isnt man enough to take them all the way flat.

I'm using a Clarke American 8.Using 50 grit,then 100 on new wood,but I have been using 40 then 100 on refinishes.I've always noticed small streaks here and there,but they were very light,not noticeable to the untrained eye.Lately they've gotten worse though,and I don't want to have to re-sand a floor because of this.So I guess I should use 40,60,then 100 on the "hard to cut" floors.