The Art of Floor Sanding (part 5)

Floor bore here again with more exciting sanding news.
Today as promised we are going to talk about 60 grit and .. The Gateway to Smoothness!!
But first to recap, in Part 4 we completed our first passes on our imaginary Victorian pine floor.
The belt sander is already back in the boot of the van and
the edger has finished it’s first lap.
The main floor is now ready for the rotary finishing machine to take over.
What are the advantages of the finishing machine coming in at this early stage ?
(Remember on our imaginary Victorian floor we have not taken the belt machine further than 36 grit.)
Firstly on larger jobs the belt machine is quickly free to move on to the next room or area, But more importantly we are only using the belt machine with our rough grit abrasives to basically flatten the floor and remove any existing finish.

Belt machines are powerful beasts that can cause marks and damage on certain floors
if they are used with finer abrasives.
This can include chatter marks and endgrain dishout .
(This is when a finer grit abrasive used on a belt sander is aggressive enough to sand the softwood but leaves the knotty hardwoods creating a wavy slightly bumpy surface)
We avoid these potential issues by simply not going there!
We use the belt machine to do the minimal amount possible to prepare the surface for the much gentler finishing sander to take over
In fact the norm is to sand the floors to 60 grit abrasive with the belt machine but we choose to usually finish on 36/40 grit before changing over to the lighter machine.
Both systems can work depending on your machines , papers and the type of floor.

So now let’s get ready to enter the gateway to smoothness!
There are a few good rotary finishing machines on the market .
The original invented by Lagler (Lagler Trio) has now been joined by others notably the Bona Flexisand .
Again everyone will have their preference and indeed there is huge variation between machines but the concepts will remain the same .
We need to remove all trace of our belt machine .
We choose a grit that will remove the diagonal sanding scratches .
In our case we will use 60 grit .
Load the machine and place our led light shining across the floor
The diagonal lines will be clearly visible .
We need to make sure those lines are totally sanded off so use the light at all times .
Work methodically .

The finishing machine can also go fairly close to the wall and should remove any edger scratches as far as possible . If the edging has been done properly -using the light to make sure we have regular scratches- then the finishing machine will do this easily .
We are now on our way to a perfectly sanded floor .