There are over 1 million fasteners in the market place today and the list keeps growing day by day. A fastener is exactly that, it fastens or attaches something by pinning, screwing or nailing. It secures an object.
You might look at a fastener and think it's small and there is not much to a fastener. However, there is a lot to a fastener. There is the material it's made out of, the type of finish, the bit type, the bit size, thread size, thread count, thread height, head type, head shape, point type and more. As you can see there is a lot to one fastener. There is so much information, you could write a book about fasteners. We don't have the time, so we are going to give you a crash course and a solid foundation to fasteners. If you have more questions, always feel free to drop us a line or ask others in our forum.
Fasteners are identified by 5 attributes:
- Thread pitch – Thread count
The first item when looking at fasteners is category of fastener. Such as wood screw, concrete fasteners, sheet metal, hex bolt and lag bolt. There are a lot more types of fasteners in the category, but these are the main fasteners you will run into.
By looking at the pictures above you probably noticed on the top of the fasteners, there are different ways to attach the fastener. This is called the drive, but don't confuse it with the head (We will cover this next). The drive is where the bit, such as a screw driver actually is inserted to drive the fastener tight. Again there are a lot of drive types, but here are the most common:
- Socket, Hex or Allen
The next item under type is the head style. Again there are a lot of different head styles to fasteners. Here are the most common types:
- Flat – Most common and used for a lot of different applications. Good for counterbore.
- Oval – Mounts just above the surface
- Pan – Flat surface under head. Good for low profile items.
- Truss – Features a large washer surface for greater holding power
- Round – Broadhead and gives the strength of a washer.
- Hex – Has a hex shape head with good surface coverage
- Hex Washer – Same as hex, but has a wider head for good holding power
Again there are a few more, but then you start getting into specialty fasteners.
The next attribute to fasteners is the material. This refers to two items. The actual material used to make the fasteners and the plating or coating applied to the fasteners. Most fasteners are made from steel because of the cost, but fasteners can be made from all most any material. As with everything else, there is a variety of plating that is used today. On the job site or at your house, you might run into probably the nine most common types of plating:
- Zinc – Excellent for corrosion resistance
- Zinc Dichromate – Excellent for corrosion resistance
- Cadmium – Excellent for corrosion resistance
- Cadmium Dichromate – Excellent for corrosion resistance
- Galvanized – Very good for corrosion resistance
- Black Zinc – Very good for corrosion resistance
- Phosphate or Black Phosphate – Good for corrosion resistance
- Chrome – Good for corrosion resistance
- Nickel – Good for corrosion resistance
Each plating serves a purpose whether it is to lower overall cost, make a fastener look good or protect it from the environments.
Diameter is the third attribute to fasteners. Diameter is how wide the shaft of the screw is. Fasteners are measured by either size number or actual measurement. If a company uses size number you will know because there should always be a # in front such as #6 (Which means the diameter is .138 or 69/500″). The smaller the number, the smaller the diameter. The number can range very high, but anything over #16 is uncommon. Most of the time a manufacturer will not use an actual measurement, they use the industry standard of the size number.
Length is the next attribute to fasteners. The length is an actual measurement. So if you see 1″ then the length is 1″. There is not anything really complicated or unusual with the length as there is with all the other attributes. One item you want to know is how they take a measurement. The measurement is from the tip of the fastener to the point of where the head sits on the material. So for a hex bolt where the head sits on top of the material, the measurement would be from the tip of the bolt to just under the head of the bolt. For a fastener designed to countersink, the measurement would be from the tip to the top of the head.
Thread Count or Thread Pitch
The last attribute to fasteners is the count of the pitch. This only applies to machine thread fasteners (A machine fastener is a fastener that takes a nut or is threaded into a tapped hole). Thread pitch measures the space in between each thread and thread count measures the number of threads per inch. Basically, it defines how fine the threads are so you can match the fasteners with a nut or hole to make sure they match.
One other item to consider is the screw points. Each fastener will have a different point. There are a wide variety of points available, but here are the most common:
- Type A
- Type AB
- Type B
- Type 25
- Type 17
Now that we know all about fasteners, we can look at any fastener and know what the manufacturer is talking about. Below is an example.
#7-9 X 2 BUGLE HEAD COARSE THREAD PHILIPS DRIVE STEEL BLACK PHOSPHATE FINISH
Well from the example above we know everything about this fastener.
- Type – It has a Philips head with a Bugle, so it's good for countersinking
- Material – We know it's made out of steel and finished or coated in Black Phosphate.
- Diameter – #7 with 9 Threads per inch.
- Length – 2″
Again there is still more to understanding fasteners, but if you understand the information above, you will be able to make better decisions on what type of fastener to buy and how to make sure you get the right fasteners.