3 ms·
The Whitworth Three Plates Method should be on anyone's list of the Greatest Engineering Discoveries of All Time. The fact that you can make a precision flat s
by Turing_Machine 5y ago
The Whitworth Three Plates Method should be on anyone's list of the Greatest Engineering Discoveries of All Time.
The fact that you can make a precision flat surface starting without any precision tools is pretty amazing at first glance.
- jacquesm 5y agomelt some metal and float some glass on it. That's a very quick way to get a nice reference surface.
- deleted 5y ago[deleted]
- cellularmitosis 5y agoFloat the glass on molten metal?
- jacquesm 5y agohttps://en.wikipedia.org/wiki/Float_glass https://en.wikipedia.org/wiki/Float_glass
- Turing_Machine 5y agoFloat glass is pretty flat, but I'm not sure regular glass is temperature-stable enough for the task (and of course, it's fragile). Temperature-stable glass (e.g., Pyrex) usually requires a lengthy annealing stage. Granite surface plates are pretty popular, though. Maybe glass would be okay for light duty. Speaking of glass, amateur telescope makers can grind mirrors accurate to within 1/4 wavelength of light, using nothing but abrasive powders and patience, but they start out with a pre-cast and annealed Pyrex blank.
- Turing_Machine 5y agoI do use a piece of float glass on my 3D printer bed, and it works well enough. Maybe I'll see if I can figure out how much it distorts when heated (not enough to cause a noticeable problem with the relatively low-precision stuff I've been making thus far). Some people do use borosilicate glass (like Pyrex) for this, but I've been satisfied so far with a piece of regular float glass window stock I had cut to size at Lowes.
- jacquesm 5y agoThere are glass compositions that are very thermally stable, this is a very well researched area because so many pieces of the science puzzle depend on it.
- jacquesm 5y agoNo, but it can get you a pretty good starting point to make something that is really flat. For instance, three pieces of float glass alternated using successively finer grains will get you insane levels accuracy in a relatively short time. To the point where you'd need a laser interferometer to detect where you still have high spots.
- SAI_Peregrinus 5y agoFloat glass is nowhere near as flat as a hand-scraped cast iron surface plate can get. Smoother, yes, but less flat.
- jacquesm 5y agoIt's a pretty good starting point though, and with a little bit more work and some powder you can get it near perfect.