Metric screw size chart pdf

In general, smaller fasteners have finer threads, so the thread count is higher. Metric fasteners are specified with a thread pitch, instead of a thread count. The thread pitch is the distance between threads expressed in millimeters.

In general, smaller fasteners have finer threads, so they have a lower thread pitch. Brass Auto Parts. Brass Inserts. Brass Fasteners. Types of Hinges. Brass Pipe Fittings. Brass Sanitary Fittings. Brass Hose Connector. Brass Camera Parts. Brass 3D Printer Parts. Don't want to do this job yourself? Let us help you find a tradesman local to you. Screw sizes are a mystery to most people so we have tried to make life a little easier with the metric imperial screw conversion chart below.

Selection of multipurpose screws — Screws available in our online store here. Most manufacturers put both the metric and imperial size on the box of screws which is very helpful, however when purchasing online, many retailers do not.

This is largely because the title of the product becomes too long and cumbersome, so something has to go. Whether you deal in old or new money, as it were, you still need to know what you are getting. This is the difference between the two and what you need to look for:. A wood screw is sized by two different numbers. First is the Gauge of the screw which refers to the diameter — the larger the number, the larger the diameter. A number 4 screw is much smaller than a number 12 screw.

It is worth noting that there is no direct link here between the head size of an imperial screw and the gauge of that screw. It is purely coincidence that, from screw gauges 6- upwards, that the gauge is close to twice the head diameter although some sources would have you believe this is how the gauge is calculated. The length is given next and it should be remembered that the length given for a screw is the length that is buried in the wood or other material, it does not include the head of a raised, or domed headed screws.

These are the basics to know when looking at screw sizes but to find out more about the thread of screws and other items you can look at Wikipedia. The length is also measured in millimetres and exactly the same as it is for the imperial system. As a handy coincidence, the Gauge imperial roughly equals the screw head size in millimetres. A 4 gauge screw will have a head that is approximately 4mm wide. This is actually quite complicated, as was pointed out by Paul, one of our readers!

Here is a more concise explanation of the relationship between gauge imperial , diameter metric in mm and Head size. The gauge imperial is half the imperial diameter in 16th of an inch of the screw head, roughly. The precise relationship of imperial screw head sizes and the gauge can be calculated. The formula is as follows:. The Gauge is 8. Above we explain that the Gauge imperial happens to have a head which is approximately the same number in mm. This is the equivalent of saying that the diameter in mm is approximately half the gauge given what the formula above states.

They both require a different type of driver which can be found below. These are the most commonly used screws nowadays, but there are great deal more so if you are not sure about which types of screws to use, see also our projects on different types of screw , We also have a great project on how to countersink. If you need to make sure that you have the right size screw for the job, then please read on below.

Please use this table to match the metric size to the imperial screw size. Please remember that the conversion is not exact, but this is generally not a problem and the margins of error are generally considerably less than your own measurements. If you are working the other way, or trying to find the metric screw size from an imperial measurement then you can use this table.

We have add the sizes for the pilot holes and rawl plugs that are generally used. For coach screws, which have a hex head the size as opposed to the length is quoted as an ISO Metric Thread. These numbers describe the thread and relate to the size of the wrench that should be used on them. Find out more about wrenches here , but here are the common thread sizes and their corresponding Spanner or wrench size.

If you are struggling to find the best way to get your screw into whatever you are screwing, then have a look at our project that explains all about screwdrivers.