> That sounds like a good thing to build - although I like the capacitor > version better because it does not include the mains voltage.
Their appeal for me is that they're instant. Squeeze the desired joint in the (heavy copper) electrodes, hit the trigger, and *pop* you have a weld. Generally capacitance discharge welders are 30-70 volts for the size of materials we'd be working with, which is less than mains voltage, but still enough to wake you right up. The oven transformer spot welder only develops a a few volts, but at many amperes. > What property makes nickel or iron the better choice? I am curious. I'm mostly thinking of tradition. There are many varieties of stainless, and some (like vacuum melted 316L) have superb vacuum performance. Some others can be porous, outgas, or sublime/evaporate/sputter during processing. Pure nickel and pure iron are both fairly inexpensive and well behaved. >> Alternatively, if you can get some large bore (20mm - 30mm diameter) lead >> glass tubing, you should be able to seal >> it directly to the stems using a crossfire or even a hand torch and some >> care. You'll probably want to anneal it before pumpdown. > > Does it have to be lead glass? Is it impossible to use borosilicate? Those stems are made from lead glass, and won't seal directly to borosilicate, which has a much lower coefficient of expansion. If you use borosilicate, you basically either have to use a frit seal (which you alluded to) or a graduated seal (which is likely not worth the trouble). >> A glass lathe would be ideal, but might be a bit expensive to start with. Or >> you could try building your own (the concept is simple, two chucks that >> rotate in synchrony). > > It is quite a problem for me, because I am concerned that the motors won't be > synchronous. Better use DC steppers. But are they fluent enough? You could use steppers, with microstepping to make the rotation smooth, but I'd use a common motor and gearing or cog belts. I tend to steal nice long cog belts and their associated cogged pulleys from defunct inkjet printers. But making a bunch of kit like that into a usable glass lathe is probably a job for an engineering student who is also a machinist. - John -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
