Seems like kind of a strange thing to say on a forum like this. Why make anything when you can buy it? I do it for the challenge. If you just want a part to get a job done, then fine. But the satisfaction of designing and making something that didn't exist before you made it.....as the ads say....priceless!
Do you also mine your own iron ore, cast & forge your own metal, make your own, nuts, bolts, screws and make your own paint. I build engines too but I buy several things I need, nuts, bolts, screws, set screws, metal, belts, piston rings, pins, roller bearings, O'Rings, pipes, spark plugs, gasket material, valves, springs, paint, oil, grease. I design my own engines I don't build kits. I never would have guessed people make every single part they need. I worked as Design Engineer for many years in factories we built special machines but never made parts we could buy like, electric motors, gear boxes, bolts, flat washers, nuts, chain, V belts, sprockets, gears, hydraulic pumps, radiators, rubber hoses, electric wire, wire connectors, electric boxes, fuses, switches, relays, etc. I know what you mean the satisfaction of designing & building something. For each his own. Have FUN. I almost forgot to mention fire clay works good in spark plugs don't add more than 3% water mix very well then hammer it to compact it very tight in the hole with home made tools.