To choose the right size wall plug, you need to know the diameter of the screw you’ll be using. Once you know the screw size, you can select the appropriate wall plug colour. It’s important to use a wall plug that is the same length as or longer than the screw you’ll be using. If the wall plug is too short, it won’t be able to provide enough support for the screw. How Much Weight Your Wall Plug Can Hold? If you are unsure about the weight capacity of a particular wall plug or fastener, it’s always best to choose a more heavy-duty option to ensure the safety of your mount. With a round headed screw the length is measured from below the head because the length is classed as the amount of the screw that will be in the material it is screwed into. In the example of the wood screw with a round head shown below, the diameter of the head (B) is approximately equal to twice the diameter of the shank of the screw (D). The depth of the head (H) is approximately equal to 3/4 of the diameter of the shank (D). Wood screw with a round head Imperial to metric screw conversion chart Screw Gauge Blue wall plugs require an 8mm drill bit for installation. They are suitable for use with screws with a diameter of 4.5mm to 6.0mm and can support weights of up to 35kg. Blue wall plugs are ideal for mounting larger items such as cabinets or heavy shelving. When installing a blue wall plug, be sure to use a drill bit that is the appropriate size to ensure that the plug is securely anchored in the wall. Additionally, make sure the plug is at least the same length as the screw you’ll be using to ensure that the item is securely mounted. Grey Wall Plug

The correct size pilot hole for a 4mm screw is 3.2mm. Using the above rule that a pilot hole should be 75-80% of the screw diameter, you work this out using this method: 4mm x 80% = 3.2mm. What Size Pilot Hole For 6mm Screw? The measurements of a screw typically consist of the diameter by the length. The diameter is usually the diameter of the shank including the thread – the outside thread diameter, this measurement is then presented in millimetres for metric screws or by gauge (see conversion tables above). The length is then defined by the amount of the screw that will be in the end material (e.g. wood). So for example, for a screw with a round head, the length of the screw is measured from below the head to the tip, but for a countersunk head, the length of the screw is measured from the top of the head to the tip. The diagram below gives an example of the difference in length between a countersunk and a round head screw: The difference in length between a round head screw and a countersunk screw. As you can see metric callouts and metric screw size charts are much easier to read and understand than imperial.

Once you figure out the meaning of each number found in screw callouts, you’ll find that reading callouts and screw size charts is a piece of cake. While it is possible to screw timber without a pilot hole, I would always recommend you do drill a pilot hole. Your project will be much neater and less likely parts of the timber will split. Does This Mean I Need 2 Holes For Every Screw? The screw length is the third and final number you find in metric callouts. It’s measured differently depending on the type of the screw head. Wall plugs come in a variety of different shapes and sizes, but the most common colours in the UK are yellow, red, brown, blue and grey. The colour of the wall plug indicates the size of the screw it can support. Yellow Wall Plug

Pro-tip, you might find some imperial callouts that contain only two numbers. These two numbers are the gauge number and screw length. In our metric screw size chart, we provide the pitch for both coarse and fine threads. 3. Screw Length Grey wall plugs require a 10mm drill bit for installation and use screws with a diameter of 5.0mm to 8.0mm. They can support weights of up to 45kg. Grey wall plugs are ideal for mounting very heavy items such as large cabinets or heavy duty shelving. When installing a grey wall plug, be sure to use a drill bit that is the appropriate size to ensure that the plug is securely anchored in the wall. Additionally, make sure the plug is at least the same length as the screw you’ll be using to ensure that the item is securely mounted. Choosing the Right Size Wall Plug Whether you’re buying screws online or in-store, if you don’t know how to read screw callouts, you’ll probably end up getting the wrong size. So, we’ll be starting by explaining how to read metric screw callouts first. This will help you use our metric screw size chart that is included further in the article. How to Read Metric Screw Sizes?A pilot hole should be big enough that the shank or body of the screw can pass through but the screw threads engage in the wood fibers. What Is The Difference Between A Pilot Hole And A Clearance Hole? For this, you are going to need 2 drills. Most people have at least 2 drills or more in their workshop. If you don’t, I do suggest grabbing another one as it will make your life a lot easier. These are the ones I use and recommend.