Have you ever had a project that requires one or more bolts and being frustrated trying to locate the diameter, thread count and, in particular, the length of bolt that you need? Do you find yourself staring at your parts bin (or the racks in your hardware store) and seeing an assortment such as this but none of these are exactly what you really need?
My solution to this problem is to make my own bolts. These can easily be custom made to fit exactly the project I am working on.
Say I want a bolt that is 3/8 inch diameter and 3 7/8 inches long with 16 threads per inch thread count (a course thread). First, obtain a 3-foot length of 3/8-16 galvanized or stainless steel threaded rod from your hardware store (many other sizes are also available).
Cut the threaded rod about 1/8 inch longer than the desired length using a hacksaw of cut-off disk saw. Adding 1/8 inch to 3 7/8 inches produces 4 inches. To cut the rod clamp it in a bench vice using two pieces of hard plastic or scrap wood to protect the threads, as in the following photograph:
Smooth both ends of the 4-inch rod by grinding on a grinding wheel or smoothing with a metal file. Grind sufficient material so it becomes 3 7/8 inches long, the desired bolt length.
If you want the end of your bolt to be a hexagonal nut, add a hexagonal nut followed by a lock washer and then another hexagonal nut. Clamp the first nut in the bench vice and tighten the second nut against the lock washer so the three components are very tight. Your bolt is finished. You can also add a thread locking compound to ensure that the pieces will not come apart.
In many of my hobby projects, I prefer to use a wing nut as the outmost nut. This makes it easier to turn with your fingers and avoids the use of a wrench unless of course, the bolt needs to be fastened very tight, in which case a hexagonal nut would be better.
While this approach takes a small amount of time the results are much easier (and cheaper) to achieve compared to shopping around at different stores and compromising on a bolt that is "good enough" but not exactly what I was looking for.
If you need a smooth shank part way along the shaft you can always file off some of the threads using a metal file or, better yet, a grinding wheel.