GRINDING AND POLISHING COMPOUNDS FOR TELESCOPE GLASS

WARNING: YOU ARE EXPECTED TO REVIEW THE SAFETY INFORMATION AT THE END OF THIS CATALOG IN ORDER TO PROTECT YOURSELF AND THOSE WHO COME IN CONTACT WITH MATERIALS LISTED IN THIS CATALOG. THEIR USE COULD BE HAZARDOUS TO YOUR HEALTH. IF YOU HAVE ANY QUESTIONS AS TO THE EFFECT ON YOUR HEALTH, OR YOU DO NOT UNDERSTAND THE INFORMATION FURNISHED, YOU SHOULD POSTPONE ANY PURCHASES UNTIL YOU CONSULT YOUR DOCTOR." STORE MATERIALS OUT OF REACH OF CHILDREN***PARENTAL GUIDANCE IS REQUIRED IN THE USE OF THESE MATERIALS.

BACKGROUND

Initially, while grinding your optics, you will be working with silicon carbide materials which are measured in grit sizes. As you progress through your grinding cycle from larger particles of silicon carbide to smaller particle sizes you will shift to grinding compounds whose particle sizes are measured in micron sizes. The final process is smoothing the surface with grinding compounds that are below a certain micron size.

Grit Sizes: Grit size (particle size) is determined by the approximate number of openings in the final screen used to size the grains. The larger the number, the smaller (finer) the particle size or grit size. The U.S. Department of Commerce defines a standard specification for abrasive grit "screened" (screen sieve with a specific mesh size holes throughout) sizes from No. 8 through No. 240 in its Commercial Standard CS271-65. The number reflects the number of holes per inch in the final sizing screen. Usually, the grit size offered by the manufacturers is a reflection of the average size within a narrow range, i.e., between the smallest particles aniline largest particle in the batch. In general, the grit size is the number of particles laid end to end that equal one inch. Refer to Newport Glass Works’s web site for a comparison chart at www.newportglass.com .

Micron Sizes: Micron size (particle size) is designated by the manufacturer who relies on microscopic comparisons, Sedimentometer, and other sizing methods. The numerical coding is opposite that for grit sizes, i.e., the smaller the micron number the smaller the particle size. The particles are usually separated into sizes by use of either hydraulic or air separation techniques. The manufacturer designates the size of its particles by comparing them to the standards .established by the particular association to which it belongs, i.e., the American National Standards Institute, the European Federation of Abrasive Producers, the Japanese Industrial Standards Organization or similar organizations. Once again, the micron size offered by the manufacturers is a reflection of the average size within a narrow range, i.e., between the smallest particles and the largest particle in the batch. For reference, a micron is equal to 1 millionth of a meter. A meter is equal to 39.37 inches. A chart is furnished at the end of this catalog to assist you in comparing grit sizes to microns and in relating these terms to your country's industrial standards.

All the materials offered here are of the highest quality and are produced by manufacturers who supply material to the optical industry in the United States.

The following is a suggested procedure in grinding a mirror. The I suggests the starting point if you have purchased a mirror and tool whose curves have been diamond generated. Please note that all blanks sold in this catalog will not have their curves diamond generated unless R has been specifically indicated or unless you requested the curves to be generated for an additional service charge.

The following is one possible approach to grinding and polishing an 8 inch mirror. The amount of abrasive and polishing material required really depends on the skill of the fabricator. If the fabricator is processing a large mirror then the grinding effort may have to start with silicon carbide powder have a grit size of 80 to increase the material removal rate.

 

THE FOLLOWING IS RECOMMENDED FOR AN 6 INCH MIRROR GRINDING PROJECT:

 

GRINDING AND POLISHING COMPOUNDS

ACTIVITY

QUANTITY (LBS.)

ABRASIVE

Roughing

Silicon Carbide Grit #80
 

Silicon Carbide Grit#120
Fining

1/4(*)

Silicon Carbide Grit#180
 

Silicon Carbide Grit#220
Smoothing

White Aluminum Oxide 25 Micron
 

White Aluminum Oxide 20 Micron
 

White Aluminum Oxide 15 Micron
 

White Aluminum Oxide 9 Micron
Polishing

Cerium Oxide (or Red Rouge)
Pitch

1-2

Burgundy or Swedish

 

THE FOLLOWING IS RECOMMENDED FOR AN 8 INCH MIRROR GRINDING PROJECT:

GRINDING AND POLISHING COMPOUNDS

ACTIVITY

QUANTITY (LBS.)

ABRASIVE

Roughing

1

Silicon Carbide Grit #80
 

1

Silicon Carbide Grit#120
Fining

1/2(*)

Silicon Carbide Grit#180
 

Silicon Carbide Grit#220
Smoothing

White Aluminum Oxide 25 Micron
 

White Aluminum Oxide 20 Micron
 

White Aluminum Oxide 15 Micron
 

White Aluminum Oxide 9 Micron
Polishing

Cerium Oxide (or Red Rouge)
Pitch

1-2

Burgundy or Swedish