30+inch+F3+Polishing+the+front+surface

Polishing of the front surface began on the 5th May 2015. The polishing tool (16 inch diameter) was used for re-polishing the 30 inch F4.6 mirror recently completed was re-pressed to the F3 curve.

After 30 minutes of polishing on the 5th May, a consistent dull shine could be seen across the whole mirror and out to the edge. This showed that the fine grinding had gone well and no really bad zones exist.

Initial polishing to be in the lap was done with the table turning but the tool pushed manually rather than using the over arm of the machine. Manually it is hard work and two people are needed to ensure our backs are not strained!

Some short video clips of the machine at work are below. These are hires videos and will take time to buffer:-











Polishing with the over arm started late on the 7th May 2015. By the end of the night a total of two hours polishing had been completed in the 2 sessions.

It is expected that around 20 hours or so. As of the 30th May 20 hours has been completed and the mirror is ready for figuring. Some time was lost over the last few weeks which set back teh completion time but overall it has gone well with the surface polishing out evenly.

The position of the tool and speed is varied to mix up the polishing strokes. Towards the end of polishing the tool was concentrated on the very edge and the middle. The large lap will be star lapped at the end of polishing to accelerate figuring and so that it can be used for smoothing during figuring also.