Refacing a saxophone mouthpiece is a complex and intricate art, most often done by trained professionals. There are several things you can do, however, that will make your reed instruments more playable. Remember that the most important part of doing this job well is taking your time and giving your mouthpiece the care it deserves. After all, there is no more important part of your saxophone or clarinet.
Place the fine sandpaper over the flat sheet of glass. Make sure there is nothing between the glass and sandpaper.
Rub the bottom face of the mouthpiece against the glass until the surface is entirely flat. This may take several minutes and will require some strength.
Blow on the mouthpiece to remove any dust caused by sanding.
Place the mouthpiece gauge against the table of the mouthpiece.
Slide a feeler gauge between the mouthpiece gauge and the mouthpiece table. Read the number where the bottom edge of the feeler stops. If the number does not match the facing curve specified for your mouthpiece, or if the two edges are uneven, your facing curve needs correction.
Grind down the two edges of the facing curve with a file until they match your mouthpiece's specifications. Be careful not to grind down too much or you might damage your mouthpiece.
Press the tip of the mouthpiece against the sandpaper, making sure the mouthpiece table does not touch the sandpaper.
Slide the tip back and forth on the sandpaper one or two times. If this leaves a line on the sandpaper narrower than the whole tip, then your tip is uneven.
Rub the tip against the sandpaper until the line on the sandpaper is as wide as the tip.
Blow on your mouthpiece to remove any dust particles.
Be very careful whenever grinding down the facing curve or table. Grinding too much could be harmful to the mouthpiece. Use extra fine sandpaper. Sandpaper that is too coarse will damage the mouthpiece.
Don't do your sanding on a glass table. You might apply too much pressure and damage the table.