How is bolt diameter measured

The diameter of a bolt is the Shank diameter, expressed in millimetres for Metric bolts. Because this is approximately the same as the Major or Thread diameter the thread diameter measurement can be used for fully threaded bolts. Fastener length is measured from where the material surface is assumed to be, to the end of the fastener. For fasteners where the head usually sits above the surface, the measurement is from directly under the head to the end of the fastener.

This is incorrect and should be avoided for two reasons. Miscommunication can result in getting a much larger bolt than needed. Head size can vary for the same thread diameter, especially in metric bolts, so even comparing heads to heads you may get an incompatable bolt.

Both nuts and washers are sized by the fastener they fit. With a nut the thread density must also match. The smaller the number the smaller the diameter of the fastener. It is very simple to measure the fasteners as there are different to correctly measure it.

The fastener cannot be measured with a ruler and you can get here the right idea about the measure of fasteners before buying. The measurement rule of major diameter — The distance from the outer thread from a particular side to the other. The measure rule of minor diameter — The distance from the bottom thread cavity from a particular side to the other. For the perfect, it is important to measure the length of the screw and bolt. Without a correct measurement, you will always end up with too long or short fasteners.

Download Guide. The length of screws and bolts are the distances from their head to the tip or blunt end of the product. All screw types are either flat on the top or bottom. Mostly the screws are flat on the bottom of the head and these are measured from the head to the tip.

Countersunk screws are flat on the top of the head and it is measured from the top to the tip. The hex and hex washer head screws are flat on the top and the bottom. But the measure is done from the bottom of the head to the tip. The oval headed screws have some exceptions in its measurement.

The measurement starts from the widest point of the head to the tip.