Feasability of glass gears?

Question

I recently saw a video where a glassblower was making something, and one of the first steps was to push the wad of molten glass down into a shaper with a number of vertical spikes, such that the result vaguely resembled a gear.

I am aware that gears can be made of plastics and wood (e.g. https://woodgears.ca/gear_cutting/index.html) as well as metals, but would glass (perhaps a stronger variant such as tempered or borosilicate glass) be suitable to make gears out of? Are there any historical examples of this?

Obviously with modern materials and techniques steel is probably the best choice in an industrial setting, but I am curious as to it's suitability as an intermediate step between cheap but quickly worn down wooden gears for rapid prototyping and metal gears for serious use. I would imagine it could be a lot easier and cheaper to melt glass in a home workshop and pour it into a mold or shape it appropriately as compared to doing the same thing with metals (keeping in mind equipment costs e.g. having to build a foundry capable of melting steel).

Answer 1

the tooth-root stresses in a gear are tensile and the teeth roots have sharp corners. This means if the glass gears were carrying any sort of load, the teeth would shear off right away.

Furthermore, the teeth faces in a meshing gear set are in sliding contact, and if any grit gets into the space between the glass gear teeth, the faces will rapidly get scored and then the teeth will shatter into a million pieces.

Finally, gear teeth have to withstand large shock loads when the gear train is slammed into engagement and starts up and/or reverses during operation. Brittle materials like glass exhibit very low toughness which means they break promptly under a shock load.

Answer 2

That's only a good idea if the gears will be rotating very slowly with almost no load.

Gear teeth undergo significant tension and compression loading, something glass is not good at handling.

Would you ever make a hammer out of glass?

Answer 3

Another point, that hasn't been mentioned: Over the time you will have some wear, which means scratches on the surface. These scratches can be starting points for cracks. That's why gorilla glass uses pressure stress in the surface.