A floor sander removes a variable amount of material, typically a small fraction of an inch, depending on the specific conditions of the sanding process.
The exact depth removed in a single pass is influenced by several factors, including the type of sander, the grit of the abrasive used, and the condition and type of the wood flooring.
Key Factors Influencing Material Removal
Understanding what affects the depth of sanding is crucial for planning a floor refinishing project.
- Grit Size: This is perhaps the most significant factor. Coarser grits (lower numbers like 20, 36, 40) are designed for aggressive material removal to level uneven floors, strip old finishes, and remove deep scratches. Finer grits (higher numbers like 100, 120, 150+) remove very little material, primarily smoothing the surface for finishing.
- Sander Type:
- Drum Sanders: These are aggressive machines capable of removing significant material quickly, often used for the initial rough passes.
- Orbital Sanders: Less aggressive than drum sanders, removing less material per pass and often used for intermediate or final smoothing.
- Planetary/Three-Head Sanders: These modern machines use multiple abrasive discs that spin in different directions. According to the information provided, "As mentioned earlier, the amount of stock an abrasive can remove is dependent on grit size. A three-head sander can enable you to run a grit sequence of around 100-150-180 and eliminate around 1/32” of material in one pass." This illustrates that even with relatively finer grits (starting at 100), these sanders can achieve a measurable depth of removal.
- Number of Passes: Multiple passes are always required, starting with a coarse grit and progressively moving to finer grits. Each pass removes a layer of material.
- Wood Condition: Harder woods remove less material than softer woods under the same conditions. Heavily damaged or uneven floors will require more aggressive sanding and passes, leading to greater overall material removal.
Typical Removal Amounts (General Estimates)
While the 1/32" figure for a specific three-head sander sequence is a useful data point, the total depth removed over an entire sanding job varies widely.
- Initial Passes (Coarse Grit): Can remove the bulk of the old finish and significant imperfections. A single pass with a very coarse grit might remove a few thousandths of an inch, but subsequent passes and different grits add up.
- Intermediate Passes (Medium Grit): Smooth out scratches from coarse grits and continue shaping the floor.
- Final Passes (Fine Grit): Remove minimal material, focusing purely on creating a smooth surface ready for stain or finish.
Over the entire process of sanding a typical hardwood floor through several grit sequences, the total depth of wood removed is often between 1/16 inch and 1/8 inch, though heavily damaged floors may require removing slightly more. Removing more than this risks exposing the nails holding the floorboards or significantly reducing the lifespan of the floor.
Practical Considerations
- Grit Sequence: Always follow a proper grit sequence (e.g., 36 -> 60 -> 80 -> 100/120) to ensure each grit removes the scratches left by the previous coarser one. Skipping grits results in a poorly sanded finish.
- Even Pressure & Speed: Maintain consistent pressure and speed across the floor to ensure uniform material removal.
- Safety: Always wear appropriate safety gear, including a respirator, eye protection, and hearing protection.
In summary, while a specific sander using a particular grit sequence might remove around 1/32” of material in one pass, the total amount removed during a complete floor refinishing project is the accumulation of material removed across multiple passes with various grit sizes, generally ranging from 1/16" to 1/8".
