Jim's Mirror Making Page 6

PARABOLIZING



The diagrams show the position of the centre of the mirror as it travels across the tool. The mirror is on top. Before parabolizing the mirror and tool should be cold pressed to ensure good contact between the mirror and the tool. The mirror (blue) is placed in the upper position. The stroke is much greater than normal. after each passing of the mirror turn the mirror slightly and move to a different position around the post, this will ensure that the surface is a circle of revolution.  For a 6 inch F8 mirror test the mirror after 10 minutes work to see how the figuring is proceeding.
 


 

Testing may reveal that the middle requires deepening. this is achieved by concentrating the polishing action on the centre of the mirror. the centre of the  mirror is worked on the edge of the tool as shown in the diagram. Go carefully this stroke so as to not go to deep.
 
 
 


 
 

The testing may show that the edge is to short. Move the mirror over the tool with large strokes as shown.



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