To measure a screw, you need its length, diameter, and thread pitch, typically using a ruler and calipers: measure length from the tip to the underside of the head (or top for flat heads) and diameter across the threads; then count Threads Per Inch (TPI) for imperial or measure pitch (distance between threads) for metric.
To accurately measure a screw, use a ruler or a tape measure. Place the screw on a flat surface and align the ruler's zero mark with the screw's head (unless it's a round-head screw, which we'll go into detail later). Measure from the beginning of the screw head to the end of the screw's thread.
How to Measure Bolts and Set Screws
Do not measure the head of the bolt, measure the threaded part, outside of the threads. If your bolt is metric, then the diameter is stated using the letter "M". For example, if your bolt has a diameter of 4mm then it is called an 'M4 bolt' if your bolt is imperial then it will be measured in inches.
The first number on a screw refers to its diameter, and the second number refers to its length. So, for example, a 4 x 40mm screw is 4mm in diameter and 40mm in length.
A 4 mm would be an M4 . On other numbered sizes, you might have to be more careful about pitch, fine vs coarse, but 4-40 is more common in my experience.
Standard metric screw dimensions are determined by the pitch and the major diameter, which as the illustration shows, is the largest diameter of the screw. Let's say it's 4mm, in which case it appears as M4 (the M means metric).
Therefore, an M2 screw would have an outer diameter of 2 mm. However, due to manufacturing intolerances, the actual diameter can be anywhere between 1.9 mm to 2 mm. M2 machine screws are typically made of steel, stainless steel, brass, nylon, aluminum, or titanium.
M3 (3mm) Thread Size.
M4 = Diameter of the fastener. 0.7 = The pitch in millimeters, i.e., the measurement from one thread to the next.
#10 screws have a larger diameter & probably will use a larger bit to drive; both of which are less likely to fail at 3”, compared to 1-1/4”.
4-40: 0.1120 or 14/125 in diameter; 40 threads per inch.
Imperial Bolts: In the imperial system, bolt diameter is measured in inches or fractions of an inch. The most common imperial diameters include 1/4″, 3/8″, and 1/2″. For instance, a 3/8″ bolt has a diameter of 0.375 inches across the widest part of its thread.
The actual diameter of an M3 screw is usually about 2.9mm, an M2. 5 screw is 2.4mm and an M2 is 1.9mm. So if you are measuring the screw yourself and your caliper says the screw diameter is 2.4mm you have to order an M2.
So in the above instance, an M2 Screw is measured under the screw head at 2mm. Generally, M2 screws are used within the manufacture of small items within electrical equipment, laptops, cameras and mobile phones.
M. 2 Screw sizes are not standardized in all systems so if the screw that is included with your Crucial SSD does not fit into the standoff in your PC you will need to contact the system or motherboard manufacturer to find out the correct sizes needed.
Thread size is M4 (4mm thread diameter) x 0.70mm pitch All the screws/nuts/washers on the homepage are manufactured by own factory.