When you need a very long bolt in a specific size, you might become frustrated with the limitations in supply. This whole process came to be when I was installing the Monitor on the back of the sailboat and needed an exceedingly long bolt to attach it to the deck. The bolt needed to be at least 7 inches long, while 8 inches would be preferable. The problem is the bolt had to be 5/16" in diameter.
They do not readily manufacture 5/16" bolts in excess of 6 inches because the forces on these bolts are so great that they could break if used in the wrong situation. Mounting the Monitor was not one of these "wrong situations", so I would be fine with this thin long bolt; as long as I could get one!
My choices were to search specialty stores for this extra long bolt and pay a premium for each or make my own! I chose to do the latter.
I ordered a 5/16" threaded rod from Jamestown Distributors and proceeded to make my bolts from this. The rod itself was only $4, but shipping was $12. This means that a set of 4 bolts would cost $4 each. Luckily, my dad also wanted to order some things from Jamestown Distributors so we split the shipping charges. Now the threaded rod was $4 and the shipping was only $6! At a total cost of $2.50 per bolt, I was well on my way toward saving money with these fittings.
The plan was simple, cut the 36 inch threaded rod into 8 inch sections and turn them into bolts! One important point with cutting threaded rod that you plan to use as a bolt later, the cut threads will usually get mangled, prohibiting any nuts from threading on. What you need to do is "refresh" the threads after you make the cut.
Refreshing the threads is simply the act of unscrewing a nut over the freshly cut threads. This is simple to do and only requires the forethought to put a nut on the rod before you make your cut. With the nut present, all you need to do is unthread it and the threads will be refreshed.
The 8 inch sections were demarcated by a set of nuts, all I had to do was cut between the two nuts and I would produce four 8 inch sections with nuts ready to refresh the threads.
A hacksaw made quick work of the threaded rod with little effort on my part. A hand file took down must of the irregularities before I proceeded to unthreading the nuts to refresh the threads.
To turn threaded rod into a "bolt" all you need to do is firmly attach an acorn nut to one end. This nut will lock onto the threads and never let go if tightened down properly.
To tighten the acorn nut onto the rod, you will need two nuts on the other side. The two nuts can be tightened by hand against each other until they gall and bind onto the stainless steel rod. With one wrench on a nut and another wrench on the acorn nut, you will be able to tighten the acorn nut onto the threaded rod to a degree much higher than could ever be achieved without the locked nuts on the other end. It is not uncommon to hear a grating sound as the acorn nut galls into the threads, locking it on forever!
With two wrenches working opposite each other, the two nuts can easily be freed and removed.
Using these simple steps, you can create a very long bolt for much less money than a regular custom made bolt would cost. Best of all, it will have threads on the entire unit, as opposed to typical long bolts with only the last inch having threads.