18thC Lens grinding lathe

Lens grinding machine, second half of 18th century, credited to Andrea Frati.

On display in the excellent Museo Galileo (Institute and Museum of the History of Science) in Florence, Italy.

Not the happiest marriage of architecture and mechanical engineering, but the early use of a gear cluster is interesting.

Some parts are missing.

A great deal of skilled work went into that machine!!

Elegant appearance, something that might be appropriate as a presentation gift for the King's workshop. It would be interesting to see it at work, and to have a look at the abrasive surface or cutter and at a finished lens surface. I have never ground a lens, and I am not familiar with mid-18th C. lensgrinding craftsmanship, so I am only guessing, but it looks to me as though this machine might not have been intended to produce state of the art work.

I assume that the lens blank was inserted into the hemisphere, which both rotated and tilted, and that the grinder was attached to the lantern pinion, which counterrotated, above it, with downward pressure controlled by the beam arrangement on top of the machine. Or is this way off the mark?

-Marty-

I wonder if they hung a weight on the beam up top between the fulcrum and the connecting rod to adjust pressure on the polishing head?

When I was in my 20s I worked for the Peerless Optical Company of Providence RI. One of my jobs was grinding "spheres" - lenses with spherical surfaces front and back usually one concave and one convex) having the same optical center. Because these were for glasses, they usually had different curves but there was no reason why you couldn't grind them convex on both sides, thus making a much stronger magnifying lens. The technique for grinding them was even simpler than that machine.... something like a potters wheel with a spike on a lever that held the lens up against a curved iron lap. You controlled it with your left hand while adding grinding powder with the right hand. The lenses were held in place by iron centers attached to the lens with melted pitch on them... to this day I wonder where we got the 1" square sticks of green pitch we used with a Bunsen burner. You could remove the centers by chilling them. We used a refrigerator but I suspect cold water would have worked. I suspect this technique had hardly changed since the 15th century.

I wonder if that isn't a machine for polishing lenses rather than grinding them. That was a fussier job and quite time consuming. We used simple machines for that. Aside from being powered by electric motors, the were not all that dissimilar.

I have seen it, very neat looking machine! That museum is a must see in my opinion.

Thanks for posting it.