Can I use scraps and parts of other products to build my own product? Like spools, pre welded metal, or bearings. New to all this, and I searched the threads, but I couldn't really find something like this. Thank you!
There is a concept in patent law called "patent exhaustion." Under this defense, an authorized sale of a patented product, e.g. by the patentee or licensee, exhausts all of the patent owner's rights in the patented product. In this situation, if you purchased the patented product from an authorized seller, you would have the right to repair that patent-exhausted product. On the other hand, there is also a concept of "reconstruction" which prevents you from remaking the patented product, even with scrap parts, after the original patented product has been "spent."
If you are making a totally different product, as others have commented, you could still be liable for infringement of any patents covering that different product.
Depending on exactly what it is that you want to do, you may want to consult a patent attorney.
Generally I'd imagine there is no particular reason from a patent standpoint why you couldn't make use of other products. In particular, I've seen artwork made from welding together scrap farm equipment and horse shoes. This doesn't mean that using scrap parts guarantees your product is immune from patent infringement. If someone has a patent on an invention and you make and sell a device using that invention, you may be sued for infringement regardless of the source of the parts. However, some companies sell parts which are covered by patents. Perhaps a special bearing for instance. They expect their customers to use those parts so you basically get permission or an implied license. It is possible that you might make use of a part in an inappropriate way that might endanger someone. Then, I suppose the original manufacturer might have good cause to try to keep you from using their parts, but that isn't strictly a patent issue.
The bigger problem is that if you aren't making one-off items like art, it would be hard to get a reliable supply of raw materials. But this is an economic or engineering concern, not a patent issue so it would be off topic for this site.