Bosch Power Tools 1821 Sanding Operations, Selecting Sanding Disc, Sanding Tips, Sanding Wood

BM 1609929Y07 10-10:BM 1609929Y07 10-10 1/18/11 10:06 AM Page 15

Sanding Operations

SELECTING SANDING DISC

Sanding discs are made of extremely hard and sharp aluminum oxide grits, phenol-resin bonded to a sturdy fiber backing for fast heavy-duty service and long life. The discs vary as to size and spacing of the abrasive grits. OPEN COAT (type H) — used for soft materials and on paint or varnish. CLOSED COAT (type K) —used for metal, hardwood, stone, marble and other materials.

Sanding discs range in grit from 16 (very coarse) to 180 (very fine). To obtain best results, select sanding discs carefully. Many jobs require the use of several grit sizes and at times both “open coat and closed coat” discs are required to get the job done faster. See chart for application examples.

Operation: Refinishing painted wood or metal surfaces.

REMARKS	GRIT
To remove paint and to smooth	Coarse
surface irregularities.	16-24-30
To smooth	Medium
the rough sanding.	36-50-80
To remove scratches left by	Fine
previous discs.	100-120
To smooth surfaces for painting,	Very Fine
polishing or waxing.	150-180

SANDING TIPS

For best results, tilt the Disc Sander at a 10° to 15° angle while sanding so that only about 1" of the surface around the edge of the disc contacts the work.

! WARNING	If the disc (accessory) is held
	flat or the back edge of the

disc comes in contact with the work, a violent thrust to the side may result.

If sander is tilted too much, sanding action will be too great and a rough cut surface or gouging and snagging will result.

Guide the Disc Sander with crosswise strokes. Be careful not to hold the sander in one spot too long. Do not use a circular motion, as this makes swirl marks. Test before use on scrap stock.

Do not force or apply pressure when sanding. Use only the weight of the tool for pressure. Excess pressure actually slows the tool down. If faster stock removal is desired, change to a coarser grit disc.

Remove gummy paint from metal with an “open coat” disc. Sand until sparks start to appear, then stop and change to a “closed coat” disc to remove any remaining paint.

SANDING WOOD

When sanding wood the direction of the disc motion at the contact point should parallel the grain as much as possible. The rapid cut of discs and the swirl type scratch pattern they occasionally create generally prohibit their use for producing the final finish.

Scratches and circular marks are usually the result of using too coarse a grit. When changing to a finer grit, move across the sanding lines that were made by a previous coarser disc.

SANDING METAL

When sanding automobiles or appliances, wipe the metal clean with a non-flammable solvent or commercial cleaner to remove all wax and grease. By doing this first, the sanding discs will sand better and last longer.

For heavy duty work, use a coarse grit disc first. Follow-up with a medium grit to remove scratches. To produce smooth finish, use fine grit disc.

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