Lot's of good advise above.
Patent the previously distributed, ("Public Domain") item? no. But there are "Proccess patents" where the specific item is unimportant.
In your instance, joining the several pieces in a truly unique manner
might be pattenable but we're pretty far along technologically for there to be any unkown processes of joining metal, from furnace brazing to friction welding and everything in between.
It's possible to whittle say a block of wax, spray it with an electrically conducting paint and have any one of many different metals plated over it, then melt out the wax, I've done it and so have thousands of others. Very useful for highly convoluted shapes of very thin wall.
If you substitute liquid refractory for the conducting paint, dip several times, melt out the wax, you can pour in any molten metal that suits your fancy. Sturm Ruger uses molten SS that way to make pistols.
Aerospace now
glues everything together. It's come full circle from when I was a kid 60 years ago and glued
my airplanes together, missed a good patent bet there, huh?
Ah but, that patent would have run out 40 years ago......
You "kids" are lucky now days, perusing the contents of the patent office online is free! For most of my years as a would-be mad inventor in California, that took a very costly patent search by a local Washinton DC guy and "he" wasn't always reliable. You can now discover if your idea is unique, all by yourself but caution, enthusiasm has a tendency to blind, you've got to be honest with yourself. When you discover prior art that seems to parallel your idea in some ways, ask yourself, "
if that was my patent and some guy tried to push this similar idea around it, would I cry foul? Is there truly something unique in my design?"
Being dishonest with yourself can make lot's of money too, for patent attoneys!
Bob