You can pretty much do anything to your tools within reason. Because your tools are specifically made from metal, to apply any further or additional changes would most likely occur in the form of machining or, through a combination of both welding and machining. When your designer initially designs the parts, he should have, in the back of his mind, already considered (or perhaps communicated) the potential areas of concern as well as any additional areas that might require further modification. These modifications or areas of concern can include areas where potential wearing of the tool can occur or stress areas that may cause the parts to break or fail once in the hand of consumers, neither of which are desirable for quality, form or function.
When your designer does finally supply you with the final drawings of your invention, he should also include a 2D drawing that further highlights and elaborates on these possible areas of concern, modifications, etc. He should also design the part in a way that makes potential adjustments or modifications easy to complete.
Take, for instance, that your designer made a hole in your part (as the invention specified) that was 15 mm in diameter. If, further into the process, you decide that the original 15 mm diameter sized hole is too small for the part in terms of form and function, you may request that the hole be made larger. Dependent on the method the manufacturer used to make your tool, this could either be a simple change or, it could be drastic enough that it may cost you a considerable amount.
First of all, when your manufacturer was first given the 2D drawings, he should have taken note that the 15 mm diameter hole needed to be considered as an area of potential development. Therefore, with this observation, he should have designed the tool accordingly in order to eliminate extensive costs for redesign as addressed in the example above. If you decide to change your tools, you will, more than likely, be paying more for the tools themselves to be adjusted; however, it is worthwhile if you are unsure of certain factors such as illustrated in the example regarding the diameter of the hole.
Making the tool as versatile as possible from the beginning of the process will not only save you time, it will also save you money. Therefore, always ensure to openly communicate with the designer and the manufacturer in terms of the intended form, fit and function of your invention. Do not be afraid to ask for further insight from your team of designers, manufacturers and invention mentors as these individuals have industry expertise that can provide valuable insight into a product’s creation and overall success. Through communication and collaboration, you can often avoid mistakes that often impose on your budget and on the progress of your invention.