I am not sure that it is worth the effort/cost. You are protecting the look and shape of your product, which is easy enough to bypass. I believe that if you sign , date and certify your drawings, you are automatically protected. People used to post a copy to themselves, so that it was postmarked with a date and leave the envelope unopened, in case it was needed.
I would draw up a non compete, non circumvention and non disclosure agreement for when you approach a suitable supplier. This will prevent them from telling others about your design, and stop them cutting you out. I can find you a template for one of these if it helps you.
If your tool is new and unique, it may well market as the "woodpig hollowing system" , "woodpig texturing tool" etc and protect itself in the same way that other named tools have. You can only get the tool from one place, it isn't a big enough item that competitors will start to mass produce it themselves and you will never stop a man in his garage making one for himself.