Hogging with machine and full size tool

[Steve Gould]

I have built myself a Mirror-o-matic grinding machine and constructed a full size tile tool.

Mirror blank I have has already been hogged but is incorrect for the "f5" I want, it is not deep enough.

What stroke length/overhang should I set on my machine?

Regards

Steve

[Astrobits]

The mirror has to be held very loosely so that it can follow the curve. If you set the overhang greater than 50% there is every possibility of the mirror tipping over the edge of the tool so max about 45% if centre over centre. With an offset then the max stroke will be less. You should get there with about 30% ( 1/3 ) stroke with a small offset.

More info would be useful.  What is the size of your mirror, Have you made mirrors before?

Nigel

[Rusted]

Hogging out is ideally a manual task because it goes very much quicker that way.

You can put some real effort into the glass and keep changing grit as often possible to keep it cutting fast.

Doing it outdoors is even better because it keeps the roughest gravel out of the optical workshop as you slosh the mud away.

Though you might have to explain to the neighbours why you are rubbing a glass dustbin lid over a smaller one.

And making a thoroughly enjoyable racket at the same time. 

I did most of my optical work on DIY machines and now regret the man hours wasted on hogging and rough grinding.

Machines are better for smoothing and polishing IMH[umble]O.