While not everything can be made by hand, without the luxury of having access to a machine shop, I'm going to go ahead and say that most things can be if one is determined enough.
Over the years, on various forums, I've read the post "I would love to build something like that, but I don't have any machine tools." more times then I care to count, and have even done it myself before seeing the light.
This page simply serves as a syndication of neat things I've seen people build without machine tools, either completely by hand or by re-purposing more common power tools.
This is something I built back in the day as a challenge to literally make a launcher from scrap materials using a hand-actuated valve.
The result is a not-so-frequently-surfacing old design based on a poppet valve, which requires at least one o-ring to operate correctly.
I used nothing but a set of jewler's files and a dremel to build this valve.
The valve "cores" on all of the launchers Tech made were built from either PVC or solid plastic stock already the correct diameter, and had O-ring grooves turned down using a drill press.
Also of note, Tech made his own HDPE pistons by turning down plastic cutting blocks.
While the pictures to this cannon are now dead due to link
rot , it was easily one of the more
impressive examples of what somebody could do with some
creativity, metal stock and tubing, and hand tools.
The Cobra Striker was the second hybrid cannon built by Moonbogg using metal construction, although instead of being welded together like his first, the Striker was pieced together from standard materials and bolts.
It was (most likely still is) a piston-valved hybrid cannon using an inline valve not seen before. More importantly than that, all of the components were made by hand without the aid of a machine shop.
I recently found some photos of the Striker on one of those "syndication-type" web sites which take photos from contributors in turn for increasing their visibility, in addition to selling the publisher's own products...
It's also fairly clear that Moonbogg knew his way around elbow-grease and metal polishes...
You can see a video of it in action here.
Nothing much to say here. BtB's creations have always inspired either envy or awe.