Many of our customers' parts are designed to be fastened together using bolts or pins. These customers often have questions about how to deal with the accuracy limitations of the waterjet process.
The short answer is that you can enlarge the hole with the right size twist drill or reamer. Since most of the material has already been removed from the hole, this is easy to do. It is easiest to do on a drill press, but it can even be done with a handheld power drill.
For instance, you might need a hole for a bolt with a 0.25" (1/4") diameter. Because the width of the waterjet stream can vary, you might end up with a hole 0.26" or 0.24" in diameter. If you have a 0.25" post or bolt, the best thing to do is to specify a size of 0.24" in diameter, then finish the hole with the appropriate drill or reamer. The exact size drill or reamer will depend upon how close of a fit you need: whether it's an interference, close running, or free running fit. For most ordinary fastening applications, an ordinary twist drill will work.
If you don't want to enlarge the hole with a drill, you're going to have to specify a hole 0.262" in diameter, and be prepared to accept that the bolt may wiggle around a bit in the hole. This is OK for many applications.
If you are unsure of the size of the bolt, pin, or post, you should double-check the diameter of the posts with a precision caliper or a micrometer.