How to measure a screw or bolt used in furniture
One of the most upsetting things when getting new furniture is getting it almost all together and then you realize you are missing a screw or a bolt. Most furniture these days comes from China, so when you call up the online store and say you are missing a bolt, they have no idea what size you need nor do they know exactly where to get it. You could try taking all of the furniture pieces apart and carefully stuffing it back in that super tight box, but all that just for one screw. Maybe you should take a trip to Home Depot and try to find the one missing screw. Now the furniture is made in China or Europe there is a good chance that you will need metric hardware. For our first example, we are going to assume that you need a screw measured with the good old Imperial system of inches, feet, gallons, and miles.
In order to replace a screw, you need to know the size, head style, point style, and material. Let's start with the size. You need to know length, diameter, and thread.
For length you measure from the point to the head. Specifically you measure to the point on the head where the screw would rest against the wood. To make it super simple, you measure to the bottom of the head for a round head and you measure to the side of the head for a screw that is counter sunk. Now that you know the length of the screw. Let's say for our screw the length is 2 inches.
The next step is figuring out the diameter of the screw. For this you measure to the wide point of the side of the thread. Let's say that at the widest point of the screw thread it is 1/4 of an inch. Now we know the length and diameter. The last piece of we need to know for size is how many threads per inch. For this sizing you measure an inch of the thread and count how many threads inside that inch. For our example, we will say that there are 20. That would make our screw 1/4-20 x 2.
The diameter is 1/4 inch the thread is 20 and the size is 2 inches.
When it comes to material, you need to know how strong you need the screw and whether or not it might get wet. If the screw is going to be exposed to the elements you might want to consider a material like stainless steel or aluminum or plastic. If it is for indoor furniture, your run of the mill cheap screws and bolts from Home Depot will be fine.
If you need a screw or bolt that is metric, the sizing is a little different. They measure the diameter of the screw in millimeters. They measure to the edge of the thread just like we do in the states. The next measurement you need for metric is pitch. This is the space in millimeters between threads. This is totally different than the US where we measure how many threads in an inch. The last measurement they have in metric is the length which as you guessed it, is also measured in millimeters.
Now the last two things to figure out is what type of point and what type of head. Let's start with the point. If you are screwing metal into metal, you probably want a flat point often referred to as a machine bolt or machine screw. As long as yioru bolt matches the diameter and pitch (thread) of your nut, you should be in business.
It gets more complicated when you need screw to pierce a material. If you need to screw into wood and there is no metal, you probably need a wood screw with a sharp point. We use wood screws that have part of the point shaved off so that they are super sharp. They pierce the wood without a predrilled hole. If you need to use a wood screw, you probably want to drill a hole that is a size or two smaller than the screw.
The last thing you need to figure out is what type of head. Should it be a flat headed wood screw that will eventually be flat with the material. Is it a bolt where the head is supposed to end up visible.
When you buy furniture from Richardson Seating you never have to worry about this problem. If you are missing hardware or lose hardware or anything happens to your hardware, we have hundreds of thousands more in our factory in Chicago. We know every part to every piece of furniture so we can quickly send you what you need. You will never end up at Home Depot for our products.