How to Charge a Lap With a Diamond Spray

Diamond-charged laps are used to cut precious stones to various shapes and sizes.

Lapping wheels, or laps, are mounted on diamond honing machines for cutting, polishing and finishing of raw precious stones. Laps are also used to sharpen tools used to carve raw stones. Before you use a lap, you need to spray it with diamond spray as the wheel itself is not abrasive and cannot cut or polish materials without the abrasive spray. Spraying a ceramic or metallic lap is known as charging a lap. You use a finer grade of diamond spray for polishing and finishing gemstones and a rougher grade for cutting stones and sharpening tools.

Things You'll Need

• Eye goggles
• Solvent or soap-based degreaser for metallic laps
• Household powdered abrasive cleanser or abrasive hand soap for ceramic laps
• Stiff brush
• Corundum abrasive
• Oil or spray lubricant (optional)
• Denatured alcohol or methanol (optional)
• White vinegar
• Spray bottle or cloth
• Light machine or cooking oil
• Facial tissue
• Motorized diamond honing lathe

Instructions

Charging a Ceramic Lap

1. Scrub your ceramic lap with powdered abrasive hand soap or household cleanser to remove debris. Brush it with a stiff, nylon brush and allow it to air-dry.

2. Shake your bottle of non-aerosol diamond spray very well. Spray oil or lubricant on your wheel if you have had experience using lubricants with diamond spray and you find that a lubricant makes it easier for you to use the lap.

3. Dilute your diamond spray with alcohol according to your experience or preference, if you wish. Fill a spray bottle with the diluted spray. Use the spray straight from the bottle if you are a newcomer to the jeweler's craft or if you are satisfied with the results it provides for the type of work you are doing.

4. Position the spray bottle nozzle diagonally a few inches above the top of the ceramic lap. Dispense a few short bursts of spray with the bottle trigger or button.

5. Hold a piece of corundum abrasive with a 1/2-inch to 2-inch flat surface against the front surface of the lap. Work the diamond into the lap by exerting pressure on the corundum until you have thoroughly rubbed the entire surface of the lap. This may take several minutes to complete and the corundum will get hot during the process.

6. Scrub the lap once again with dry abrasive hand soap and a nylon brush. Rinse it with water. Brush the lap to remove any debris.

7. Allow the lap to air-dry. Apply a generous coat of undiluted white household vinegar to it with a spray bottle or a clean cloth. Allow the vinegar to evaporate.

8. Mount the ceramic lap securely on your honing machine according to the manufacturer's directions. Turn the power on and set your machine to moderate speed.

9. Spray the lap twice with the same grade or dilution of diamond spray you used in Step 4. Stop the machine and use a piece of facial tissue to wipe off any excess.

10. Use your lap to finish your diamond and make sure it produces a white cream as you polish. If it does not, repeat Steps 8 and 9 to apply additional spray, but do not apply too much diamond spray as you will clog the lap and scratch your stone.

Charging a Metallic Lap

1. Remove oil or rust preventative from your metallic lap with a solvent or detergent-based metal degreaser according to the instructions on the package. Completely dry the lap with a clean cloth.

2. Shake your bottle of diamond spray and dilute if desired.

3. Mount your lap on your honing machine and secure it to the machine according to the manufacturer's instructions. Turn your machine on and set the power to medium.

4. Spray six to eight bursts of diamond spray onto the lap while it is moving. Turn the machine off and let the liquid from the spray evaporate.

5. Spread two or three drops of light machine oil or cooking oil onto the surface of the lap with your fingers. Work the spray into the lap by lightly rubbing the lap in a circular motion with a carbide abrasive. Do not use a carbide abrasive wheel or block with sharp edges.

6. Turn the honing machine on and hold the abrasive against the wheel for a minute or so. Turn the machine off.

7. Wipe the lap with a clean cloth to remove excess abrasive and oil slurry. Coat the lap carefully with a thin coat of oil.

8. Use the lap for polishing. Add a drop of oil if the surface becomes too dry.

Tips & Warnings

• Prepare heavily used metallic laps that are glazed and have a shiny surface by grinding the surface or using a dressing stick according to the manufacturer's instructions before you charge it with diamond spray.

• Wear eye protection when using a lap on a moving honing machine.

References

• Gem World; Instructions for Charging Ceramic Laps; Jack Slevkoff; 1996
• Glendo Corporation: Instructions for Charging and Use: Cast Iron Lap