Prepare for Sanding Flooring
PREPARING THE FLOOR FOR SANDING
Sweep the floor clean immediately before sanding. Inspect the floor carefully - tighten any loose boards by face nailing with flooring cleats or 6d to 8d flooring nails, preferably into joists, look for any protruding nail heads or nails not driven down below the wood's surface, pull them out or counter-sink them with a nail set and replace any damaged or defective flooring boards (sanding exposed nails can produce sparks creating a fire hazard in the sander dust bag).
SANDING A NEW STRIP OR PLANK FLOOR
Load the drum sander with a coarse grit to medium grit sandpaper. Place the machine along the right hand wall (unless making an angle pass) with about two- thirds of the length of the floor in front of you. Start the motor with the drum raised off the floor, walk slowly forward at an even pace and ease the drum to the floor. As you near the wall at the end of the pass, gradually raise the drum off the floor. Practice before turning on the machine.
Cover the same path you made on the forward cut by pulling the machine backward and easing the drum to the floor as you begin the backward pass.
When you reach your original starting point ease the drum from the floor. Move the machine to the left side approximately three to four inches. Then repeat the forward and backward passes and move to the left after completing each set of passes. You will only sand a 3" to 4" wide strip of un-sanded area with each set of passes. When the two-thirds area of the room is sanded, turn the machine in the opposite direction and sand the remaining third in the same manner. Be sure the sanding passes made in the one-third area overlap the first passes by two to three feet. This blends the two areas together.
After completing the first sanding operation, or "cut", with the drum sander, use the edger to sand along the baseboards, up to corners, in closets, and other areas the drum sander did not reach. With new flooring, which is relatively smooth, use the next grit sandpaper that will be used on the drum sander. With old flooring it may be necessary to use the same grit paper as the first drum cut to remove old finish or level abused areas.
If a medium grit cleans and sands the floor completely, use it for the first cuts. If extra passes are required to clean and level the strips go to a more coarse grit paper. The first cut with drum sander and edger should produce a level, completely sanded floor (with corners and obstructions to be scraped later). All following sanding procedures merely remove the sanding scratches produced by the first cut.
When using the edger move in an easy quarter-circle pattern at end walls overlapping into the drum sanded area 4"-6", and following the direction of the grain, to some extent. (See Figure 5.) Do not try to make the edger cut more aggressively by putting extra pressure to the front. This merely makes ridges and grooves which are hard to remove. Along walls parallel to flooring direction, move back and forth with the direction of the flooring, also overlapping into the drum sanded area. The edger typically cleans a 1" to 2" strip on each pass.
After drum sanding the floor with a coarse grit sandpaper, repeat drum sanding with a medium grit sandpaper. For the edger, use fine grit sandpaper. If coarse was used on the first cut use medium grit and follow with fine grit on the edger. Complete the sanding operation using the fine grit sandpaper on the drum sander.
Generally, filling of nail holes, blemishes, cracks, etc., should be done before the fine sanding cut. Use a commercially prepared wood flooring filler. Some fillers may need coloring or may not take a bleaching operation; check with the supplier or manufacturer.
Also, it may be necessary to trowel fill the entire floor, particularly an old floor, due to the extent of cracks between strips. Multiple character marks found in #1 and #2 COMMON Grades which are fillable grades may also require trowel filling. Trowel filling should be done before the medium or final sanding cuts. Let the filler dry thoroughly before proceeding with the sanding. (Overnight is best.)
When drum sanding and edging are completed proceed to hand scrape and then hand sand corners and around doors and other cased openings. Also hand sand the perimeter edges. Use the same grit as the last cut. Using a sanding block or electric oscillating sander can facilitate the hand sanding process. If staining the floor a dark color, the electric oscillator may leave egg shaped marks which will show in the stain. Hand sand these out or do not use the oscillator.
When using a hand scraper apply even pressure, scraping in the direction of the grain. Avoid gouging the wood with the scraper. A brick with a piece of old blanket glued around it makes a good sanding block. Sand about 6" into drum sanded area. Always sand and scrape in the direction of the grain along the length of boards.
Using a sanding disc (one grit finer) or screen disc (same grit as fine cut) on the buffer over the entire floor can also improve blending of edged and drum sanded areas. Move buffing machine back and forth with the direction of flooring boards.
If the floor is to be stained a light to medium color, the fine sanding cut with 80 grit sandpaper leaves the wood fibers open and enables more stain to penetrate, producing a deeper shade and more uniform appearance. An option is to screen with an 80 grit after the fine sanding cut, particularly if the fine cut was 100 grit. Use of the buffer and screen increase the risk that circular scratches will show if a dark stain is applied.
Three sanding cuts followed by screening or discing is the recommended procedure and will provide a uniform surface for most all standard finishes. Two cuts followed by the screening or discing operation may be sufficient but may produce a more coarse surface and is considered a minimal sanding procedure.
SANDING PARQUET, BLOCK AND SIMILAR PATTERNED FLOORING
Use the drum sander and edger for two sanding cuts. With the first cut do not sand directly across or with the pattern but always on an angle. Start the first sanding cut diagonal to the grain using a medium grit sandpaper. Then use fine grit sandpaper for the second cut on the opposite diagonal. Use the buffer and screen or disc to make a final fine cut with the room's longest dimension. (See Figure 7.) (A coarse first cut is usually not necessary.)
REFINISHING AN EXISTING FLOOR
Most oak flooring is 3/4" thick and can be sanded and refinished a number of times. Thinner solid oak floors - 1/2" or 3/8" thicknesses - should be refinished with caution because repeated landings can wear down the groove edge, causing breakage or wear through to reveal nails. With laminated flooring, professional sanding is recommended.
To determine the floor thickness remove a floor heating register or the shoe mold and baseboard so that an edge of the flooring can be measured.
When refinishing floors, remove as little of the surface as is absolutely necessary. This is particularly true with veneered and thinner floors. On square edge strip flooring that is face-nailed, all nails must be driven slightly below the surface of the wood to permit sanding.
The following instructions apply to standard 3/4" strip, plank and block floors and, with the cautions just mentioned, to the thinner materials.
Sanding. It may be necessary to use a very coarse "open coat" paper to remove the old finish. The heat and abrasion of the sanding operation make the old finish gummy and may quickly clog normal sanding paper. First try regular paper (particularly on a diagonal). If 90% of the finish is removed and the floor is generally flattened, coarser grits are not necessary. When you get down to new wood use the same procedures and grits as previously described under "Sanding a New Strip or Plank Floor". If the old floor has been painted several times it may be necessary to use paint remover to uncover the wood surface.
The number of sanding passes required for "Refinishing" will be largely determined by the condition of the old floor and the thickness of the finish being removed. If the surface is in very good shape, with only light scratches and few dents, and has no build-up of old finish and wax, one pass with the disc sander and fine paper may be sufficient. Be sure all the old finish is removed.
If the floor has been abused, scarred or dished, use as many cuts as are necessary to get a smooth, unblemished surface. If badly scarred and abused boards have not been repaired, it may be advisable to leave some blemishes in the floor or too much sanding may be required.
With a floor that is in fair condition, make the first cut at a 45°± angle to the flooring direction with medium grit paper to level the floor and remove 90% of the finish. Then follow the instructions given for sanding a new floor on the succeeding cuts. Use the same grit paper as was used on the 45° cut for the first cut parallel to the flooring strips.