Sheet Metal Screws vs. Wood Screws
I'm getting ready to mount my solar panels to my 5ver roof. It's 3/8" plywood. I'm planning two screws per bracket and four brackets per panel. I bought stainless steel screws for the mounting and pla...
Forum Discussion
As a professional tradesman who has worked with both wood and metal for 43 years, I can attest to the fact that wood screws are NOT always just for wood and sheet metal screws are NOT always for just sheet metal.
When a person becomes well seasoned in his trade he rapidly learns that every project is different and varied. Every project requires the analysis of the situation and then a judgement call on what works best for this current situation.
A wood screw DOES have an unthreaded portion at the top of the shank. They are designed this way as a wood screw to hold 2 pieces of wood together, the design being to have the unthreaded portion of the shank to rotate freely through the attaching piece of wood to that which it is attached to. This is what they are made for. If the screw has threads to the top, it is generally not a wood screw, except in a random few specialty applications. It is a sheet metal screw.
Sheet metal to sheet metal, it is the design of the sheet metal screw to be threaded to the top in order to secure these 2 pieces together. In many cases, but not always, a self tapping screw is used. A self tapping screw has a drill point on the end designed to create a hole in the metal for the screw threads to follow through.
A tapping screw can be used here as well. It is the same as a sheet metal screw. A sharp point and threads all the way to the head. These are most commonly used on thinner sheet metal such as aluminum flashing or things like furnace ductwork. When the metal is thin enough, a self tapping or self drilling screw is not needed. On thicker metal, such as aluminum extrusions, the self tapping screw works best. And this especially holds true when fastening a thinner piece of aluminum sheet goods to an extrusion, such as in the 2500 plus aluminum patio covers I have erected in my 43 years of this industry.
I could go on about this but won't.
Back to the OP's situation here, this falls into the category of a custom application, fastening a thin aluminum bracket to wood.
As previously stated, you must not use a wood screw, even though you are going into wood. You must use a sheet metal screw through the aluminum into the wood, as it is the only screw that will suit the need here. You must have threads go to the top of the screw. In other words, a sheet metal or tapping screw. A wood screw will not work in this situation. The shank of the wood screw will spin out in 3/8" of wood.
When a person becomes well seasoned in his trade he rapidly learns that every project is different and varied. Every project requires the analysis of the situation and then a judgement call on what works best for this current situation.
A wood screw DOES have an unthreaded portion at the top of the shank. They are designed this way as a wood screw to hold 2 pieces of wood together, the design being to have the unthreaded portion of the shank to rotate freely through the attaching piece of wood to that which it is attached to. This is what they are made for. If the screw has threads to the top, it is generally not a wood screw, except in a random few specialty applications. It is a sheet metal screw.
Sheet metal to sheet metal, it is the design of the sheet metal screw to be threaded to the top in order to secure these 2 pieces together. In many cases, but not always, a self tapping screw is used. A self tapping screw has a drill point on the end designed to create a hole in the metal for the screw threads to follow through.
A tapping screw can be used here as well. It is the same as a sheet metal screw. A sharp point and threads all the way to the head. These are most commonly used on thinner sheet metal such as aluminum flashing or things like furnace ductwork. When the metal is thin enough, a self tapping or self drilling screw is not needed. On thicker metal, such as aluminum extrusions, the self tapping screw works best. And this especially holds true when fastening a thinner piece of aluminum sheet goods to an extrusion, such as in the 2500 plus aluminum patio covers I have erected in my 43 years of this industry.
I could go on about this but won't.
Back to the OP's situation here, this falls into the category of a custom application, fastening a thin aluminum bracket to wood.
As previously stated, you must not use a wood screw, even though you are going into wood. You must use a sheet metal screw through the aluminum into the wood, as it is the only screw that will suit the need here. You must have threads go to the top of the screw. In other words, a sheet metal or tapping screw. A wood screw will not work in this situation. The shank of the wood screw will spin out in 3/8" of wood.
