1. Cutaway view of the two pieces to be joined.
2. Clamp the two pieces together and drill a hole the proper size (see chart below) for the bolt you will be using.
a. To make sure you do not go through the top side, measure the total width and mark the drill bit with a piece of tape.
b. The threaded hole must be deep enough that the bolt will hold – about 1.5 times the width of the bolt is minimum, more is better.
3. Using the first hole as a guide drill out the hole in the bottom piece so the bolt can slide snugly into it.
4. Tap the hole on the top piece using the proper tap (see chart below).
Alternate methods of Bolting
5. Blind bolt: Bolt the two pieces together.
6. Blind bolt with countersunk head: This is a good method to attach a piece to a base. It is removable, clean looking, and strong providing there is sufficient depth to thread the bolt. Countersink the head of the bolt using a third drill. You will have to use a bolt with a hex or torque head. These are available as specialty bolts.
7-8. Hiding the end of the bolt: If there is not enough room for a blind bolt as shown, you can drill all the way through and, using a bronze bolt (available at marine hardware stores) hammer the end of the bolt like a rivet.
a. Once the bolt is in place, cut it off so that it protrudes above the surface about 1/2 its width (a 1/4” bolt should stick up about 1/8”).
b. Hammer the end of the bolt with a ball peen hammer to mushroom it so that there will be no gap between the bolt and the metal.
c. File or use a disc grinder to sand the surface flat. The bolt should disappear.
d. The edges of the hole do not need to be beveled in this case as the threads hold the pieces together.
(See the Tap and Drill Chart below)