Recommended stroke for hogged mirror and tile tool

[Garyh]

Hi Folks,
Just a quick question before I start on my new mirror.
The blank is hogged out to about f/5 (with a old pipe fitting) and I have made a tile tool to suit the shape. The mirror is not very spherical more like a hole in the middle.
Just wondering what stroke would be recommended to get things back more or less to a spherical shape. I am hoping to get the mirror to about f/4.7 when complete.
cheers and thanks for any advice..:thumbsup:
Gary

[Satchmo]

Hi Gary
Start by working away the `shoulder' area ( the edge of the hole ) on the edge of the tool, chordal stroke style. Once the curve is looking much more spherical , alternate MOT ( mirror on top) and TOT with say a 1/4 length W stroke until sphericity is obtained. If you want shorter FL spend a bit more time MOT . You can observe the behaviour of trapped air between the blanks to get a handle on their sphericity. Hope this helps.

[Garyh]

Thanks Mark for that info....
using the pipe fitting does hog the middle out well but leaves the edges very flat...shall start with that chordal stroke...:thumbsup:
cheers Gary