Questions about mechanical parts

1. For the main frame, I see Dave and others weld the frames in addition to tightening with screws. Is it a must for welding? Locally, we need a license to weld! (which we obviously lack as students)

2. About the motor. I have a motor as belows, planning to reduce its speed with reducer. The power should not be a problem. But:
(a) How can I couple this shaft to a worm? How exactly do people call these shafts with a notch?
Ans: They are called keys and keyways. Keyway couplers serve the purpose well.

(b) Is it a monophase or triphase motor?
Ans: This is a monophase motor because triphase ones don’t use capacitors and there are only two power connections in the wiring (U1 and U2).

1: No need to weld, I just prefer to make it solid. But i’ve seen others making a frame with bolts and nuts as well. JUst make sure its strong
2: Depends on the outcome of both shafts. We like to make a metal connector on the lathe. But i’ve seen other interesting methods coming by on the forums like flexible rubber connectors and detachable ones.
3: I dunno…

@wkhs just in case you wonder, I too have a motor with keyway, and I got my Jaw Coupling from here:

*20mm coupling (for the hex bar): https://www.amazon.com/gp/product/B003HIWPBE/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
*Spider (goes between both jaw couplings): https://www.amazon.com/gp/product/B003HIWQN6/ref=oh_aui_detailpage_o04_s01?ie=UTF8&psc=1
*25mm coupling (this was the diameter of my motor’s shaft): https://www.amazon.com/gp/product/B003HIWPCI/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

I would recommend to weld everything together to make sure its strong and solid. Specially the shredder has to deal with heavy forces. But you can always try first to see how it goes without welding. Kind of curious myself
That is a coupler!

1: Thanks @davehakkens! How about the shredder parts? It’s not a must to weld, I guess? (Except, well, the sieve perhaps…?)

2a: I have found a specialized coupler for these “keys”. See the attached for the nomenclature

2b: I got an answer from the excellent stackexchange.