screws plugs and drill bits?

What are the recommended screw and drill bit sizes for the yellow, red and brown rawl plugs, in metric and imperial.

How are screw sizes measured, eg 2 and half by 10. I think 10 is the head size and 2 and half the length, but how do you know which size plug for this.Is the bigger the head the wider the screw?

Thank you.

14 Answers

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  • Screw sizes run 4-6-8-10-12 1/4inch (4 through12 fractional parts of 1/4 inch) and indicate the screw diameter. The rawl plugs should give the required drill size on the box. If not a good rule of thumb is the plugs should be a tight fit an tapped in with a hammer you can try this on a scrap piece of wood. Others have responded to the drill size I’m not sure. Usually the head size increases with the screw diameter, there are special applications but this the normal way they run.

  • 1

  • The plugs are for fixing screws into masonry, so the drill you are using is a masonry drill. These are usually sized in Metric diameters, and the diameters correspond to the plug sizes.

    Screws are sized in ‘Guage’ (width of the threaded part) X Length (which can be in mm or inch). The guage sizes approximately correspond to appropriate hole & plug (metric)diameters. However, different combinations of ‘masonry’, thread profile, and plugging materials can affect the ‘fit’ of a particular screw.

    Unfortunately, there are no standard colour codes for the sizes, but I think that Rawlplug use (in the UK) brown for an 8 and red for a 6.

    Some other manufacturers make all their plugs in the same colour, but helpfully mould a number into the plug, which indicates the correct drill diameter. Some plugs are also supplied moulded onto a ‘card’ or a ‘spine’, which will often include funny-shaped holes or cutouts that are meant to act as a guide to selecting the right plug & hole diameter for different screws.

  • In your example, 2 1/2 x 10, 2 1/2 is the length of the screw in inches from the point to the surface of the wood when the screw is fully inserted. For a countersunk wood screw that means from the tip to the top of the head. For a round or cheese head screw that means from the tip to the underside of the head. The 10 is the imperial gauge of the screw at its widest point. A number 10 screw is about 5mm in diameter at its widest point, while a number 8 is about 4mm in diameter. The lower the number the thinner the screw and vice-versa.

    Yellow plugs use a 5mm – 6mm drill, red use 6mm – 8mm drill, brown 7mm – 8mm and blue use 10mm – 12mm. There are a multitude of other different plugs for all sorts of uses, and all require their own size of clearance hole.

  • Yellow – 5mm

    red – 6mm

    brown – 7mm

    SIze of the screws measures the head and width, the higher the number the wider the screw. eg size 10.1.

    2.5 – length of the screw.

    Yellow plugs are hardly used unless you go to diy shops. They will have a small discreet screw poss a size 6.

    The reds you can use up to size 10 comfortably anymore and I would reccomend a brown.

    Brown plugs are very good for 4inch 10’s or 12’s, they grip very well.

    You can get blue and green strip plugs which you cut to size but that is another kettle of fish.

    The most common plug is the red plug which needs a max hole of 6mm.

    Hope this helps

  • Wall Plug Sizes

  • Brown Rawl Plugs

  • Yellow is 5mm drill bit And the screw that fits its a 6

    Red is 5.5mm/6mm drill bit and the screw that it is an 8

    Brown is 7mm drill bit and the screw that fits that is a 10

    21/2 x 10 = 2.5 inches (Length*) x 10 (Girth*)

    *=Of the screw

  • Normally only use the brown wall plugs , then you need a 7mm drill

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