Quote:
Originally Posted by stephend
Thanks,
Satchmo raises the issue of grinding vs finishing. As I understand it, grinding produces a spherical surface. The longer you grind, the smaller the radius of the sphere. The surfaces obey universal entropy; spherical is the profile of lowest energy they can mutually assume. It's easy to understand and fairly easy to do. This I have done.
Finishing turns this cross-section into a parabola. I haven't ever done this. Can someone explain what principle is involved in turning the spherical profile into a parabolic one. Also, what sort of work. I gather it can be done quite quickly but takes some skill.
Astrojunk, those books sound great ... it's just the ... cost! 
Bolts_Tweed, if that Elgin machine worked, what's it doing in the garden collecting rust? Why aren't you grinding mirrors with it?! Must say I'm surprised a car windscreen wiper motor has enough power. Ingenious!
Cheers |
Three ways
1. Deepen the centre
2. take material off the edge
3. Do a bit of both.
Method 1 is the "classical" way of doing it by lengthening the polishing strokes so that the centre gets more work done on it and so deepens.