using a diamond disk for hogging

[CharlesM]

Some years ago I'm certain I read somewhere about using a large grinding disk held at a shallow angle to hog out a mirror blank.
I believe the disk has to be larger in dia than the blank and a method of calculating the angle of the blade to the work to produce the desired radius of curvature was shown.
Does anyone know of this or am I dreaming

[sharkbite]

https://www.thefreelibrary.com/Rough+grinding+the+easy+way%3a+say+ goodbye+to+the+drudgery+of+hogging. ..-a0268651894

Hi Charles...is this what you were looking for?

[CharlesM]

sorry but no, but thanks for the heads up.

[mura_gadi]

Closest I found was this on youtube, the rocker box I assume is set to your sagitta curve. I would not be using anything as high powered as shown, your dust control would be hit and miss at best. Such a brutal approach will lead to some very deep fissures, you could be releasing extra material from the face for a very long time in the fine and smoothing stages of grinding.


I'd be far more inclined to suggest an old steel bar weight about 1/2 diameter of the disk and go down to 40grit. You should manage around 1mm an hour or close too, the bar weights grind out very well and 10/15/25kg of weight helps a lot with the abrasion... Dropping back to 120+ when approaching the last stages of the hog will help limit the size of fissures and fractures cause by the larger grits.

Some grits cause greater fracturing at the glass surface than others at the same grits size, ie silicon carbon v oxides. Be fair to say the same of different wheels as well.

https://www.youtube.com/watch?v=NA5fP73_0T4