How do we sort and classify loose stones ?

Loose stones are first sorted by geometric shape (crystal, macles, elongated etc). These are further broken down into size and quality (number and degree of imperfections).

Does the colour of a stone have any bearing on its hardness or abrasive quality ? if so, what?

In general, the colour of a diamond does not hav any effect on the hardness or abrasive quality of the stone.

There is one minor exception : Some brown diamonds tend to be less vulnerable to chipping in certain application.

This does not amount to much in practice, since all diamonds are brittle and will chip easily,if mishandled.

Why are reset stones generally darker, less lustrous in appearance?

Generally after a diamond has been used, a certain amount of detrimental heat and pressure result in some chemical cracks and graphitization of diamond.

This is also true to a very minor degree in the procedure used to set the diamond in the matrix.

Does a diamond's surface smmothness influence tool performance?

Surface smoothness will have no detrimental effect on the performance of an unlapped dressing tool.

It will hav a definite on the overall performnce of a lapped tools (boring, turning, diaforms hoggluds etc).

What criteria are used to select the best point of a diamond?

The point of each diamond is selected for its degree of sharpness, structural strength and lack of detrimental flaws.

One must realize that a diamond is not aisotropic like glass.Diamond has a grain structure and is therefore very resistant to abrasion along a certain axis.

We as a diamond tool manufacturer, try to mount each diamond so that in the dressing action the grinding wheel runs against these axes.

Does coning weaken a stone ? Is there such a thing as skin hardness?

It is generally accepeted that coning does weaken a stone somewhat due to removal of the sharp axis along its edges.

This weakening may be further explained by removal of material mass to create the necessary included angle in a coned point dresser.

Yes this skin has a definite bearing on tool use, particularly on the coated octahedron or congo diamond.

This skin is apparent to the naked eye on this the of diamond and is actually a coating of diamond of different makeup than the original stone.

It is normally not as fully crystallized or as a hard as the central crystal due to its later geological forming.

What is the significance of point included angles?

Point included angles will vary depending on the form or profile to be dressed in the wheel.

It is generally accepted that included angles on the diamond should never be less than 60 degrees on a coned type diamond or less than 40 degrees on a lapped tool.

It is general rule of thumb to use as wide an included angle as the profile will permit.

What are realistic acceptable natural radius specifaications for single points? Will the grain size of my grinding wheel have any effect on these points?

Practical radius specification vary greatly depending upon the application.

These may range from .002 - .005 on thread and gear grinding to .020 - .030 on large centreless or external grinders.Unfortunately, there is no generally accepted for mula to define the exact radius needed for a particular application.

Yes, wheel grain size will have a bearing on natural radius needed and the impact of shock created by large grained wheels, it is a general rule that the larger the grain, the larger the radius needed and vice versa.

Do all diamonds forms (crystals, octahedrons, etc) have the same hardness?

Yes, all pure diamonds have the same testing hardness but in practical usa not the same abrasion resistance. A particular type of diamond may outperform another in a particular grain structure.

Abrasion resistance is attributed to the great energy required to break the atoms always from their tetrahedral arrangement.

If the improper type or shape diamond is used, it may offer its soft axis to the grinding wheel thus decreasing its potential life.

How do we determine the size of diamond needed for a particular application? do u know of any formula that can be applied to derive the proper diamond size to be used?

Most manufacturers base their recommendations individual or past experiences rather than a formula.

There are several mathematical formulas available, however we have found that the appliacation of such formulas result in the use of a larger than necessary stone.

What are the practical wear limits for single points tools?That is, how much or how large wear flat generated is tolerable?

A single point diamond should never be overused. it is generally accepted that once the wear land of the dressing face exceeds. 040 in diameter, its efiiciency and effectiveness are greatly reduced.

Proper indexing or resetting are then needed to avoid damage to the diamond or its bonding matrix.

What temperature can diamond withstand? when does graphitization begin and what is the effect on stone performance?

At approximately 100 degree F (870 degree C) in an ordinary atmosphere, it will withstand temperature as high as 2900 degree F (1590 degree C). In actual use, this is a contracy surface phenomenon.

it is detrimental in the dressing cycle when extreme heat and pressure are created by too great an in feed, cross feed or lack of the proper coolant flow. When this occurs, graphitization begins and the diamond's abrasion resistance is eliminated.

Is there any difference in the processes used to reset diamonds as opposed to that used in the manufacturing of new tools?

The processes used for new tools and resets are identical. The only significant difference is that a reset stone has to be removed from its original matrix, and re-oriented to it its next best point.