CHAMFERING TOOL.

After the first time beveling a mirror edge I decided there was a quicker and easier way of doing it as well as making a nicer job. I built an attachment for my grinding machine with an emery wheel set over at 45 degrees. I gave this away too much setting up. I have also beveled with a diamond wheel when I was diamond milling mirror blanks. But the simplest and best is a cast iron tool to do the job. It can be used on a machine or by hand. I drew up the tool made a pattern, had a cast iron casting made and machined it. The drawing below shows the details of this and how I machined it. I scribed an arc of the correct radius on 3mm aluminum sheet, cut it on the bandsaw and sanded it to the scribed line. I machined the back of the cast iron ring first. Then turning it round I freehand machined the radius to the template. I used the power feed on the cross slide of the lathe and hand fed the compound rest. I used a radiused tungsten carbide tool. When I had it fairly close I clamped a piece of 5/8" square steel in the tool post and set it up close to the curve as shown in the drawing. I used a high speed steel wood turning tool by hand to smooth out the curve. The edge of the template was blued and moved back and forth on the surface to mark the high spots which were then scraped off .

In operation I have the mirror rotating on a spindle. I wet the curved surface of the tool and sprinkled 220 carborundum powder on it. Placing the tool over the mirror I wobbled it around to grind the bevel, replenishing the powder when necessary. This takes only a couple of minutes and gives a smooth even bevel to the edge. The operation can be performed off a post and it is not even necessary to walk around it or rotate the tool, just wobble it.

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