We do not recommend the aluminum bracket for fireplace mantels thicker than 3 inches (and in some rare cases 3.5". Beyond this you will encounter issues with the set screws), or deeper than 4.5". In general, fireplace mantels are usually thicker than 3-4 inches. The longest set screws we have found are 3 inches long. Besides this, drilling the pre-hole and the tap to make the thread for the set screw through 3 inches of wood can become very imprecise. In addition, in order to install a mantel with the aluminum bracket, the wall will need to be reinforced.
This is why we have the steel bracket, and the various sizes it is offered in (notably, height). Because of this height difference, the set screws can remain between 5/8 and ¾ length.
Some of our customers try to use the Aluminum bracket to install fireplace mantels. In theory this is not a problem as long as you use set screws. But to use only glue is very dangerous and generally unsafe. We strongly discourage anyone from doing so.
An alternative, and in fact the only alternative, is to use a metal bolt that is inserted from the top through the mantel, and then through the top of the female bracket and at least through the ledge of the male bracket. The best option would be to even have the bolt go through the bottom of the female bracket and back into the wood.
You can use it as a feature or countersink the head of the bolt. You can use a magnet to get it out again, or you can countersink it so much that you can fill the hole with wood putty. If the bolt is too thick it will only be ¾ through the ledges. This is not safe. It has to be a clean hole through male and female bracket ledge.
But even this alternative has its limits if the wall is not reinforced. Since the amount of weight that 4 pan head wood screws #8 (2 ½” long) can hold in 2 studs is not nearly as much as lag bolts in connection with the steel bracket.
Below: Incorrect Bolt Placement
Below: Correct Placement
Looking to learn more about the Steel Hovr Bracket? Head over to the Steel Bracket FAQ here.