We just got a multi-head sander. What grit sequence should I use with it?
Mark Dittmer, Midwest regional manager at American Sanders, answers:
All the multi-head sanders on the market today have really changed the world of wood floor sanding, making the sanding process easier, and this is probably the most common question I get from wood flooring pros.
When I had my contracting business, for a typical floor we would sand with 60 and 100 on the big machine, then go right to 120 on the buffer. Most guys would use either a screen or a hardplate for their buffer, and the perimeters would have to be scraped and then hand-sanded (and now most pros use a random orbital sander for the wall lines).
Always going from the big machine to the typical buffer is no longer the standard process for many pros, but there isn't one answer on how to change your sanding process and grits once you start using a multi-head sander. Some contractors today are finding they can use their big machine less, stopping at 60 with their big machine and going right to their multi-head. Some are also finding that the multi-head sander is able to fix some imperfections left by the big machine, such as minor chatter.
Another helpful change with the multi-head sanders is that they get very close—about a half inch—from the wall. If you are working on a job that is new construction or otherwise has the base removed, you can eliminate the random orbital step entirely.
No matter which sequence you end up starting with on the multi-head, you still want to end with the same grits as you always have (most commonly 100 for natural floors and 120 for stained floors). Contractors also need to take into consideration the type of sandpaper they are using (black, red, blue, etc.) because different abrasives will leave different scratch patterns on the final sanding. In the end, you have to find out what you are most comfortable with on the particular multi-head sander you have (including with and without weights, if it has them). I always tell pros they need to get a variety of different discs and experiment until they find a process that works for them.