In June 2016, the NWFA released updated guidelines for the sand and finish processes.
One of the areas that was updated involved sanding direction using the big machine (belt or drum sander):
- Old guideline – the first cut with the big machine should be at a 7-15 degree
angle to the length of the boards.
- New guideline – the first cut with the big machine should be at a minimum 7-15 degree angle to the length of the boards.
More aggressive angles (up to 45 degrees) may be necessary to achieve a flat surface in extreme cases. Wider plank floors, excessive overwood/underwood or uneven flooring systems may benefit from a steeper angle first cut. The more uneven the flooring surface, the steeper the angle of the cut should be. When the first cut exceeds a 15 degree angle, the subsequent straight cut must be made with the same grit paper used on the first cut at the exact opposite angle.
- Old guideline – when sanding parquet patterns the first cut should be at a diagonal; the second cut should be on the opposite diagonal using the next appropriate grit of sandpaper and the final sanding cut with the big machine should be parallel with the room’s longest dimension, using the last sequenced grit, not skipping more than one grit between sanding cuts.
- New guideline – The first cut should be at a 45 degree angle to the wood grain; the second cut should be on the opposite angle to the wood grain using the next appropriate grit of sandpaper. All subsequent sanding cuts with the big machineshould remain at an angle to the wood grain to prevent dish-out of the material. The cut angle on the floor will be dictated by the many variations in grain direction, species and condition of each individual floor. Use the last sequenced grit, not skipping any grits between sanding cuts.
These changes were made by suggestions of many of the subject matter experts within the wood flooring industry to help ensure a higher quality end-result in the final sanded product. The direction of the cut from the big machine (drum or belt sander) is the first step in ensuring a properly sanded, flat floor.