Original+TRO+Making+the+tools+for+grinding+by+hand

The books I have read indicated that a tool for grinding and polishing might be made out of plywood, faced with ceramic tile. This would then be sealed against water prior to use. This method was decided upon with a sub diameter tool size of 17 inches, slightly over 1/2 the diameter of the mirror. Quarry tiles were initially going to be used but because they were very hard and uneven on the back I decided to use standard white tiles. These were cut into 2 inch squares and all edges bevelled. The cell was covered in plastic and the mirror put in place. Car body filler was smeared all over the face of the flat wooden tool on bottom face. Parchment paper (grease proof or similar) was placed on the mirror in the centre. The tool was then placed on the mirror and pressed firmly down so that the filler took the shape of the mirror curve. This was done twice to get a smooth surface. The surface of the filler, when dry, was covered in 4 minute epoxy and the ceramic tiles pressed into place. When the epoxy was dry the edge of the tiles where dressed to shape and bevelled using an angle grinder fitted with a stone grinding wheel.



A problem soon arose with this tool configuration. After a few hours work and the glaze had worn off tool was wearing down too quickly and was not doing any useful work. Th tool was modified by covering the tool again with filler to reset the curve and then covered in thick 1.5 inch diameter metal washers. This idea came off the internet but was similar to an idea I had heard off from Peter Drew of the AAC who said people had used old pennies in the past. The surface was again covered in epoxy and the washers arranged on the surface. See section Evening out the irregularities left by roughing out Above shows the grinding tool used after hoging out. The convex suface is covered in metal washers fixed to the suface by epoxy glue.

Original TRO Introduction and concept Original TRO Purchasing the blank and hoging out Original TRO Testing the curve for accuracy Original TRO Making the tools for grinding by hand Original TRO Evening out the irregularities left by rough grinding Original TRO Polishing and testing Original TRO Making the mount and tube assembly Original TRO Making the secondary flat Original TRO Aluminising the primary mirror Original TRO First light