ABOUT OUR GRANITE

FREQUENTLY ASKED QUESTIONS:

Different kinds of stone are used to make granite surface plates: Black granites and gray, light gray and pink granites.

Black granite is generally accepted as the best because of its lower porosity and moisture absorption, superior strength, lower coefficient of thermal expansion, uniformity of texture and non-glaring surface.

STANDRIDGE produces granite products from several types of granite, depending on the customer's needs. Laboratory tests have shown that fine-grained black granites are stronger, denser, and less absorbent than other granites. For this reason precision machine bases, air-bearing surfaces and accessories are best made from black granite.

Our knowledgeable staff can assist you in selecting the best granite for your product, based in regard to uniformity of surface, accuracy, deflection under load, type of use and price.

Lighter colored gray granite is excellent for large surface plates and machine bases because of its availability and lower price.

All light colored granites are less than one-third quartz; the remaining constituents of light granites are as soft or softer than black granite. The textural uniformity of black granite results in more even wearing qualities. The uneven wear of light colored quartz granite may allow quartz crystals to abrade tools and gages moved about the surface plate after the softer constituents have worn away.

• Uniform hardness
• Accurate under load
• Nonmagnetic
• Vibration absorbent
• Easy-to-clean
• Maintenance free
• Nonabrasive

• Warp resistant
• Rustproof, noncorrosive
• Plates may be easily resurfaced
• Nonglaring
• Low porosity
• Thermal stability

The black granites used in STANDRIDGE products are selected for dense structure and low absorption rate. Low porosity provides an easy-to-clean surface that resists stickiness, an essential property in ensuring surface accuracy. Because low porosity resists changes in humidity, black granites tend to be more stable than water-absorbent granites.

Because black granites contain no crystalline quartz, they have a very high modulus of elasticity, producing a superior load-carrying capacity. Black granites have uniformly fine textures and tight porosity, characteristics which make this igneous rock extremely resistant to water absorption or warping from humidity. The superior "stiffness" of black granites is highly desirable for surfaces where accuracy and stability are essential.

Black granites are 50 to over 100 percent stiffer than light colored granites based on Young's Modulus of Elasticity. Minimum deflection of flatness accuracy can be guaranteed with less thickness in black granites than in light colored granites. Result: you pay less for freight and handling whenever the plate is shipped or moved.

Black granites will respond less than other granites to temperature changes that may distort the accuracy of the plate.

Pink and gray granites absorb 3 to 4 times the moisture that black granite does, based on immersion tests. The more porous granites will absorb and release sufficient moisture because of temperature and humidity changes to sometimes rust metal tools or parts left on the surface plate. This is virtually unheard of among black granite surface plate users. Black granites are much less likely to stain than the lighter colored more porous granites.

Use softeners when moving your surface plate. Do not lift load on bottom edges. 
The plate must be lifted level.

Do not place surface plate under heater or air conditioner vents as it alters the surface accuracy.

It is essential that your surface plate is supported on 3 points to minimize sag and warp. Match the 3 points on the stand to the 3 points under the surface plate.

When placing your granite surface plate on the steel stand, please locate as follows:
Nameplate on surface plate should be placed on end of stand with single suspension point.

Your granite product may be cleaned with soap and water, or any detergent, and/or by rubbing on a small amount of waterless lanolin hand cleaner. Granite must be dry before using. We also suggest our PREMIUM GRANITE CLEANER which penetrates the granite surface to loosen dirt, grime and residues. It leaves the surface clean, allowing instruments to slide without the resistance that wears down the precision surface.

As a standard procedure, all of our surface plates are checked for cracks. There may be color streaks or nature lines, which are an abundance of mica and iron formed during the granite's molten state which in no way affects the guaranteed accuracy.
STANDRIDGE can assure that the structural integrity of our granite is guaranteed for life.