If you find a market for your product, the best thing, in the world, is to have someone manufacture it for you (machine shops can do this). Get quotes from several, in your town, with how much production, they can "guarantee" (stuff breaks, people get sick, etc.. You can't ever assure someone any number of parts all the time).
It's best if they make it, deliver it to you and you deliver it to your customers. You are the middle man that cannot be cut out because you have the patent. No one can build and sell those parts without your written consent. All you do is ship your stuff out and make the money. Let your vendor (the machine shop) take the losses and headaches of broken tools, bad parts, etc..
If you take your idea to a shop, without a patent, and have them build it, the shop will patent it and you cannot stop them from selling it without a non-competition agreement. If the shop does a bad job, you can't go somewhere else and have it made, because they have the patent. If production needs become huge, you can take your patented idea to 10 shops and have them build the parts anywhere you want.