- Joined
- Dec 6, 2012
- Messages
- 2,677
Below is a cut/paste excerpt from this link:
www.cwu.edu/~cattinw/_private/Documents/Surface Plates.doc
I find the history fascinating.
History
Ancient Egyptian pyramids and buildings bear testimony to man’s early understanding of flatness as the basic reference plane from which dimensionally accurate heights, angles and squares could be obtained.
The length of the sides of the great pyramid varies no more than 1/20 of one percent from the mean length of 9,069.45 in. This is remarkable accuracy, considering overall size and the number of blocks of stone involved.
It is believed that the Egyptians, in leveling the foundations for their pyramids and buildings, flooded the area with water using the surface of the water as a reference from which to determine overburden removal or fill-in to make the land flat and parallel to the surface of the water on top of it. Nature does not provide a flat surface in the raw. Even the surface of a body of water will tend to be curved by the forces of gravity and atmosphere as the length and width increases. Flatness can not be taken for granted. Remember that in ancient Egypt, as opposed to today, the earth was flat!
In an effort to produce flatter surface plates, we are confronted with devising the best method to use on a material that has properties that will preserve the flatness produced.
In the evolution of methods, gravity has been used to fix a flat surface on material that solidifies after being in a fluid state. Among these are cement, glass, ceramics, cast iron, and steel. Each has properties that make them unreliable for extended use. They lack stability, resistance to wear and corrosion or defy ultra fine surface finishing obtaining greater flatness.
The first machining method that could produce duplicated parallel surfaces on metal was Richard Robert’s invention of the planner in 1817. Today precision surface grinders and lapping machines do the production work in flattening a surface to known accuracy.
Henry Maudslay, who invented the first screw-cutting lathe in 1797, is credited for being the first to produce flatter surfaces by hand filing and lapping with abrasive particles. He produced master-reference surface plates by working three plates against each other.
[FONT="]By 1874 Sir Joseph Whitworth had introduced hand scraping instead of abrading to improve the three plate method of producing a flat surface.[/FONT]
www.cwu.edu/~cattinw/_private/Documents/Surface Plates.doc
I find the history fascinating.
History
Ancient Egyptian pyramids and buildings bear testimony to man’s early understanding of flatness as the basic reference plane from which dimensionally accurate heights, angles and squares could be obtained.
The length of the sides of the great pyramid varies no more than 1/20 of one percent from the mean length of 9,069.45 in. This is remarkable accuracy, considering overall size and the number of blocks of stone involved.
It is believed that the Egyptians, in leveling the foundations for their pyramids and buildings, flooded the area with water using the surface of the water as a reference from which to determine overburden removal or fill-in to make the land flat and parallel to the surface of the water on top of it. Nature does not provide a flat surface in the raw. Even the surface of a body of water will tend to be curved by the forces of gravity and atmosphere as the length and width increases. Flatness can not be taken for granted. Remember that in ancient Egypt, as opposed to today, the earth was flat!
In an effort to produce flatter surface plates, we are confronted with devising the best method to use on a material that has properties that will preserve the flatness produced.
In the evolution of methods, gravity has been used to fix a flat surface on material that solidifies after being in a fluid state. Among these are cement, glass, ceramics, cast iron, and steel. Each has properties that make them unreliable for extended use. They lack stability, resistance to wear and corrosion or defy ultra fine surface finishing obtaining greater flatness.
The first machining method that could produce duplicated parallel surfaces on metal was Richard Robert’s invention of the planner in 1817. Today precision surface grinders and lapping machines do the production work in flattening a surface to known accuracy.
Henry Maudslay, who invented the first screw-cutting lathe in 1797, is credited for being the first to produce flatter surfaces by hand filing and lapping with abrasive particles. He produced master-reference surface plates by working three plates against each other.
[FONT="]By 1874 Sir Joseph Whitworth had introduced hand scraping instead of abrading to improve the three plate method of producing a flat surface.[/FONT]
