No 4 screws

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Size of Screws and Metric to Imperial Screw Conversion Chart and How to Identify the Diameter and Length of Imperial and Metric Screws

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.

Screw selection and assortment

Metric and Imperial Screw Sizes

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:

Screw size label

Imperial Screw Sizes Explained

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.

Screw size label

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. There’s a lot to learn if you’re interested!

Metric Screw Sizes Explained

As you can imagine, the metric system is a little simpler to understand for the uninitiated however if you’re not used to it, or still working in Imperial it can be a little tricky.

Rather than use a “Gauge” figure, the metric system uses the (major) diameter in millimetres. 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:

(Head diameter in sixteenths is an inch X 2 ) – 2 = Gauge. E.g. 5/16 head times two equals 10, minus two equals 8. 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).

Don’t worry if you don’t follow this as not many people know about these relationships, let alone use them.

More about Screws

Slotted screws are fast becoming history and cross head screws are now the fashion but it must be remembered that a cross head screw can either be a Philips screw (top image below)or a pozidrive/supadrive screw (bottom image below). They both require a different type of driver which can be found below.

Phillips head screw
Pozidrive head screw

Although technically you can use a Phillips driver on a Pozidrive screw and vice versa, their not really designed to fit and under torque load (when you are screwing the screw in) in pretty much all situations it will slip and damage the head of the screw making it difficult to either screw in the screw or remove it, so it’s always best to use the right tool for the job.

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.

Metric Imperial Screw Conversion Chart

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.

Diameter (mm)Length (mm)Closest Imperial Size
Gauge x Length
3mm124 x 1/2
164 x 5/8
204 x 3/4
254 x 1
304 x 1 1/4
404 x 1 1/2
3.5mm126 x 1/2
166 x 5/8
206 x 3/4
256 x 1
306 x 1 1/4
406 x 1 1/2
4mm128 x 1/2
168 x 5/8
208 x 3/4
258 x 1
308 x 1 1/4
358 x 1 3/8
408 x 1 1/2
458 x 1 3/4
508 x 2
608 x 2 3/8
708 x 2 3/4
4.5mm259 x 1
309 x 1 1/4
359 x 1 3/8
409 x 1 1/2
459 x 1 3/4
509 x 2
609 x 2 3/8
709 x 2 3/4
759 x 3
5mm2510 x 1
3010 x 1 1/4
3510 x 1 3/8
4010 x 1 1/2
4510 x 1 3/4
5010 x 2
6010 x 2 3/8
7010 x 2 3/4
7510 x 3
8010 x 3 1/4
9010 x 3 1/2
10010 x 4
6mm3012 x 1 1/4
4012 x 1 1/2
5012 x 2
6012 x 2 3/8
7012 x 2 3/4
7512 x 3
8012 x 3 1/4
9012 x 3 1/2
10012 x 4
11012 x 4 3/8
13012 x 5 1/8
15012 x 6

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.

GaugeMetric diameter (mm)Pilot Hole size (mm)Masonry Rawl PlugHole size for Rawl Plug (mm)
32.51Yellow5
431.5Yellow5
63.52Red6
842.5Red (or Brown)6 (or 7)
1053Brown7
125.53.5Brown7
146.54Blue10

Spanner or Wrench Sizes

For coach screws, which have a hex head the size (as opposed to the length) is quoted as an ISO Metric Thread. This is the number starting with an “M”. 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.

ISO metric threadSpanner size (mm)
M1.63.2
M24
M2.55
M35.5
M47
M58
M610
M813
M1017
M1219
M1624
M2030
M2436
M3046
M3655
M4265
M4875
M5685
M6495

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.

The sizing of screws in one of the most challenging things, but there are also a huge variety of different kinds of screw that can be used for a wide range of different job.

It is always best to get the right type of screw for the job, so we have written a project specifically about this. Have a look here for our project on the different kinds of screw you can buy.

In most cases, it is also very handy to know the different parts that make up a screw and the types of head and thread available, for information on this see our parts of a screw project here.

The M Rating or M Measurement for Screws and Bolts

On some screws and bolts you will see an M followed by a number.

M6 and M8 coach screws

The M apparently stands for Metric which sounds plausible, although we cannot verify this. What it indicates however it that the number following it is the diameter of the screw (or bolt) in millimetres.

In the examples shown above of coach screws available in our store, the M6 is a 6mm wide screw (at the threaded part, not the head) and the M8 is 8mm wide.

Other Acronyms and Abbreviations used to Describe Screws

There are a range of acronyms and letters that you often find on screw boxes or in their online descriptions. Here is a summary of the most common, and what they mean:

  • ST – Self Tapping; These screws have a tip that will allow them to be screwed into (typically wood) without a pilot hole being drilled. This saves a lot of time!
  • TT – Twin thread
  • TFT – Twin Fine Thread
  • ZP – Zinc Plated; These screws have been plated with zinc to stop them becoming corroded
  • ZYP – Zinc and Yellow Passivated; Zinc plated to reduce susceptibility to corrosion and then a passivation layer is applied to the zinc coating to give it even more corrosion protection; this typically results in a yellow colour

All project content written and produced by Mike Edwards, founder of DIY Doctor and industry expert in building technology.

Sours: https://www.diydoctor.org.uk/projects/screwsize.htm

One of the popular items in the tool shed of any DIY enthusiast is screws. They come in different sizes and shapes.

When it comes to screws, there are two primary areas where people get confused. There are sheet metal screws and wood screws. Another is understanding the difference between metric screw sizes and imperial screw sizes. The following screw size chart will ensure you understand the difference.

Contents

Different Types of US Screws

Before you look at the different US screw sizes, you need to understand the type of screw available. The following is a breakdown of three major types of US screws you can find:

Wood Screws

They are designed for connecting items to a wooden base (e.g. attaching metal coat hooks to a wooden rail).

Wood expands and shrinks depending on the surrounding temperature. This means a specialized screw is required for wood applications.

The best options are screws that bend before snapping. Wood screws have this capability and that is why they are not used on sheet metal. The wood screw comes in a variety of sizes which are provided in the tables found later in this guide.

Sheet Metal Screws

They are typically sturdier and stronger than their wooden counterparts. They can be used in other materials apart from metal as they will stay strictly in place once screwed on.

Often they are self-tapping meaning that they may not always need a hole drilled into the source before they are inserted. Sheet metal screws come in several different sizes and styles.

Phillips Head Screw

A traditional (“flat”) screwdriver cannot be used on sheet metal cross head screws. It is a cross-shaped head kind of screw (see image). Most sets of driver heads or screwdrivers have at least one of these types of screwdrivers.

screw sizes

Screw Acronyms

In addition to length of the screw, screw diameters / major diameter, and gauge size, the packaging of many screws contains acronyms. These are given to show the added value of the item you purchase.

The next step is to understand popular screw acronyms. This information will help you further understand the screws and their sizes:

  • ST- Self-tapping: They don’t require a hole to be drilled and are time savers.
  • TT-Twin thread: It’s generally more secure if a screw can be installed and removed faster than a single thread equivalent that’s what it means by two threads.
  • TFT-Twin Fine Thread: They are a little less coarse than non-fine thread screws and thus may slot into a drilled hole a little easier.
  • ZP-Zinc Plating: It offers a layer of protection against corrosion.
  • ZYP-Zinc and Yellow Passivity: They are named for their yellow coating and have two layers of protection.

Understanding Screw Sizes

Unless you are conversant with the several screw sizes that are quoted on the packaging, sizing the right screw might be difficult in both metric and imperial. We normally deal with different sizes of screws and conversion from metric to imperial sizes in this project using our handy conversion table.

The table helps in converting metric screw sizes to imperial and vice versa easily. It, therefore, makes sure that you obtain the correct ones.

Imperial and Metric Screw Sizes

Many companies put both imperial and metric size on the same box of screws which is very helpful. However, when buying online in the United States, most of the retailers do not. The main reason is the title of the product becomes too long and cumbersome meaning something has to go.

It is, therefore, crucial for you to know the difference between the two. It will ensure you minimize or avoid getting the wrong sizes.

Explanation on Imperial Screw Sizes

A screw for wood is sized by two distinct numbers, first is the gauge of the screw which is the diameter. This means, the larger the number the larger the diameter. Therefore, a number 12 screw is larger than a number 4 screw.

It is important to note that there is no direct connection between the gauge of an imperial screw and its head size. Although some sources may make you believe that this is how the gauge is calculated, it is by chance that from screw gauge 6 and above the gauge is almost twice the diameter’s head.

It is important again to note that the given length for a screw is the length that is buried in the wood or any other material but the head of a raised screw is not inclusive. The screw size is determined by length and gauge.

Explanation on Metric Screw Sizes

Though the metric system is a bit simple to understand for the unskilled, it can be a bit challenging if you are not conversant with it or still working in imperial.

The metric system uses the diameter in millimeters instead of using a “gauge” table. The same as in the imperial system, the length is measured in millimeters.

It is by coincidence that the gauge is approximately the size of the screw head in millimeters. A 6 gauge screw will have a head almost equal to 6 mm wide.

Correlation between diameter (metric in mm), gauge(imperial) and head size is complicated. There is nowhere you will find information that can guarantee you can calculate this effectively. It may be the reason why professionals prefer to buy screws personally, to ensure they get the right screw head.

The imperial diameter (in 16th of an inch) of the screw head is twice the gauge (imperial). The formula below can be used to calculate an estimate of the screw head sizes and the gauge.

Gauge= (Head diameter in sixteenths of an inch X 2 ) – 2. E.g. 5/16 head times two equals 10, minus two equals 8. The Gauge is 8.

The above formula means that for imperial gauge, the diameter in mm is almost half the gauge. You should not be disappointed if you do not follow this since not many people know about the said relationship leave alone using them.

Since slotted screws are being outdated, the crosshead screws are now replacing them but it is important to note that a cross head screw can be either a superdrive/pozidrive or a Philips screw.

Conversion Chart For Metric Imperial Screws

screws comparison
Screws and their bolts

The table below can be used to match the imperial screw size to the metric size. You should note that the conversion is not exact and therefore margins of errors are allowed.

Diameter (mm)Length (mm)Closest Imperial Size
Gauge x Length
6mm15012 x 6
13012 x 5 1/8
11012 x 4 3/8
10012 x 4
9012 x 3 1/2
8012 x 3 1/4
7512 x 3
7012 x 2 3/4
6012 x 2 3/8
Diameter (mm)Length (mm)Closest Imperial Size
Gauge x Length
5 mm10010 x 4
9010 x 3 1/2
8010 x 3 1/4
7510 x 3
7010 x 2 3/4
6010 x 2 3/8
5010 x 2
4510 x 1 3/4
4010 x 1 1/2
3510 x 1 3/8
3010 x 1 ¼
2510 x 1
Diameter (mm)Length (mm)Closest Imperial Size
Gauge x Length
4.5 mm759 x 3
709 x 2 3/4
609 x 2 3/8
509 x 2
459 x 1 3/4
409 x 1 1/2
359 x 1 3/8
309 x 1 1/4
259 x 1
Diameter (mm)Length (mm)Closest Imperial Size
Gauge x Length
4 mm708 x 2 3/4
608 x 2 3/8
508 x 2
458 x 1 3/4
408 x 1 1/2
308 x 1 1/4
258 x 1
208 x 3/4
168 x 5/8
128 x 1/2
Diameter (mm)Length (mm)Closest Imperial Size
Gauge x Length
3.5 mm406 x 1 ½
306 x 1 ¼
256 x 1
206 x ¾
166 x 5/8
166 x 5/8
Diameter (mm)Length (mm)Closest Imperial Size
Gauge x Length
3 mm404 x 1 1/2
304 x 1 1/4
254 x 1
204 x ¾
164 x 5/8
124 x ½

screw tip

Image of a typical superdrive/prodive screw.

You can as well use the table below to find the metric screw size from an imperial measurement. The sizes for the rawl plugs and pilot holes have been added.

GaugeMetric diameter (mm)Pilot Hole size (mm)Masonry Rawl PlugHole size for Rawl Plug (mm)
146.54Blue10
125.53.5Brown7
1053Brown7
842.5Red (or Brown)6 (or 7)
63.52Red6
431.5Yellow5
32.51Yellow5

A chart for the above table:

us screw sizes

Figure 1.: Chart for imperial measurements. The X axis is the gauge size. The Y axis is measurement in millimeters.

Wrench Sizes Or Spanner

The table below shows common sizes of thread and their equivalent wrench or spanner size. For screws which have a hex head such as coach screws, the size is quoted as an ISO Metric which is the number starting with “M”. The numbers are used to describe the thread and relate it to the size of the spanner to be used on it.

Spanner size (mm)
M6495
M5685
M4875
M4265
M3655
M3046
M2436
M2030
M1624
M1219
M1017
M813
M610
M58
M47
M35.5
M2.55
M24
M1.63.2

A chart for the above data

screw sizes chart

Where to Find Professionals

If you are looking for professional help with your home improvement project, use this resource to find the best qualified professionals in your area:

FAQs

How Do I Know The Best Screw Size for my Needs?

Trial and error usually! You will have to assess which size best serves your project by trying a variety of different sizes starting with the longest.

Is Machine Screw Size Important?

Yes! A machine screw that is too long or too small for your task is no use at all as it may be dangerous. Don’t cut off the end of your screw if it does not disappear fully into its source whilst leaving the ability to tighten. Use an alternative with a shorter length after you remove the machine screw in question.

Can Sheet Metal Screws be used in Wood?

Due to the flexibility of a wood screw, it may be stronger on wood. However, it may end up snapping if the surrounding temperatures change drastically.

Can Wood Screws be used in Sheet Metal?

No! Always use a sheet metal screw because the tensile strength of a wood screw cannot compare.

Can I Use the Same Type of Screws Outdoors and Indoors?

If you plan to use the screws outdoors then look for a screw labeled ‘exterior’ of the same. They will not corrode or rust as quickly in the rain because they have extra protection against the elements.

Do I Need a Screwdriver if I Have a Self-Tapping Screw?

It is advisable to have one on hand because it depends on what you are driving the screw into.

How Do I Loosen/Tighten a Screw?

Turn a screw anti-clockwise to loosen it and clockwise to tighten.

How Tight Does the Screw Need to Be?

Ensure that a screw is turned as tightly as you can manage because a loose screw could lead to a loose connection.

What Happens When My Screw Doesn’t Tighten?

Consider adding a little glue if you are screwing into the wood and you know that you have the correct style and size.

Is There a Formula for Matching Screw Sizes to Drill Bits?

It depends on whether you will be drilling into soft or hardwood, or if you’ll require the use of walls plugs in a foundational part of your home. The most effective drill bit you want to use means you need a variety of screw sizes at hand and work using the drill bit size as a guide.

Bottom Line

To size a screw is a very challenging thing but there are different types of screws you can use for a wide variety of different tasks.

In many situations, you may find it challenging to know the head and the thread available and also the different parts that make up a screw. Also take note of the number of threads per inch. Use this guide to simplify the process and reduce the margin of error.

Categories Home ImprovementSours: https://happydiyhome.com/screw-sizes/
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UK Screw Sizes

Screws are undeniably the most populous item in the tool shed of any DIY enthusiast, coming as they do in a multitude of different shapes and sizes.

There are two primary areas of confusion when it comes to screws, however; the difference between wood screws and sheet metal screws, and the eternal struggle of understanding imperial vs. metric screw sizes. This guide will assist with both of these problems.

SaleBestseller No. 1
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  • INCLUDES VARIOUS SIZES: This wood screws set includes a total of 780 bulk wood screws in a variety of lengths and widths, thus providing you with a handy assortment to choose from when drilling and screwing.
  • DURABLE & DEPENDABLE:Hardened, yellow zinc passivated and thoroughly tested, our chipboard screws have been designed to produce a tight screw and hold up well when unscrewed/screwed back again.
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T.K.Excellent Phillips Flat Head Wood Screws...
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  • Wood screws neatly packaged in a plastic clear box,Conveniently Portable, this box can handy reusable.
  • Most used 6 sizes(inch) :#6x1/2",#6x3/4",#8x3/4",#8x1",#8x1-1/4",#10x2".
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SEQUAL® Box of 200 High Performance Multi Use...
SEQUAL® Box of 200 High Performance Multi Use...
  • QUALITY: Super Drive is a new breed of professional woodscrew. It has been developed to meet the needs of a technologically advancing building and DIY trade. Super Drive’s knurled thread eases driving and maximises holding power. It can be used to secure even the latest MDF and chipboard materials.
  • FEATURES: Ribbed self-countersinking head to give a flush finish. Industry standard crossed recessed head. Hardened steel for high torque loads. Knurled thread increases drive speed by up to 20%. 40 degree thread angle to give maximum pull out resistance. Fully threaded under 70mm for maximum holding power. Type 17 point for easier starting in all timbers.
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TIMCO Solo Woodscrews 5.0 x 100...
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  • 40° deep single thread to provide a secure fixing with high pull-out resistance
  • 25° sharp point and single lead for a fast start and improved thread acceptance
  • All sizes up to and including 75mm are fully threaded and lengths 80mm and above all have 70mm thread length
Bestseller No. 6
Screws Pack, 800 Pcs Self Tapping Screws...
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Bestseller No. 7
Forgefix MPS430Y Multi-Purpose Pozi Screw - Zinc...
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  • Countersunk heads for flush fit
  • Four additional points of contact, and does not have the rounded corners
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800 Pieces M2 Self Tapping Screw Kit 4mm 5mm 6mm...
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Bestseller No. 9
Forgefix MPS4560Y Multi-Purpose Pozi Screw - Zinc...
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  • Suitable for use with many materials including PVCu, Timber, Chipboard, MDF, and other similar types
  • Countersunk heads for flush fit
  • Four additional points of contact, and does not have the rounded corners
  • Zinc yellow Passivation process of electroplating
  • Single threads, designed to offer higher pull out values and quicker insertion
Bestseller No. 10
TIMco 250IN Index Hex Head Timber Screw 6.7 x 250...
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  • Patented lubrication, designed to enhance screw insertion time and provides greater resistance to corrosion
  • Helix shank for removing debris and to improve clamping
  • 50° deep single thread to provide a secure fixing with high pull-out resistance

What is a Wood Screw?

Wood screws are designed for connecting items to a wooden base (for example, attaching metal coat hooks to a wooden rail).

The reason for a specialised screw in such circumstances is that wood shrinks and expands depending the temperature around it, and as a result these screws are flexible and will bend before snapping. You may get away with driving a metal screw into wood, but not vice versa – woods screws are not designed for use with sheet metal. Wood screws come in a variety of sizes, which are profiled in the tables found later in the guide.

What is a Sheet Metal Screw?

Sheet metal screws are typically stronger and sturdier, and as a result should be used in anything other than wood as they will stay strictly in place once applied. Sheet metal screws are often self-tapping which means that they may not always need a hole drilled into the source before use, and come in a number of different styles and sizes.

What is a Phillips Head Screw?

Some sheet metal cross head screws cannot be used with a traditional screwdriver, and instead need what is know as a Phillips head screwdriver. Any set of driver heads that you purchase from a DIY shop will contain at least one of these.

Popular Screw Acronyms

In addition to length and diameter or gauge size, the packaging of many screws contains acronyms that denote any added value to the item you are purchasing. The most popular acronyms that you will come across are:

  • ST, which stands for self-tapping – these screws are time savers, as they typically do not require a hole to be drilled.
  • TT, which stands for twin thread – two threads mean that a screw can be installed and removed faster than a single thread equivalent, and generally be more secure.
  • TFT, which stands for Twin Fine Thread – fine thread screws, as the name suggests, are a little less coarse than non-fine thread screws and thus may slot into a drilled hole a little easier.
  • ZP, which stands for Zinc Plating – this offers a layer of protection against corrosion.
  • ZYP, which stands for Zinc and Yellow Passivated – these screws have two layers of protection, and are named for their yellow coating.

UK Screw Sizes – Imperial vs. Metric

There is something of a divide throughout the UK between those who use the metric system for measurements, and those who prefer to stick with imperial equivalents.

  • Metric screw sizes provide a diameter and length in mm.
  • Imperial screw sizes provide a gauge size and a length in inches.

Some screws will have both types of measurement on their packaging, but not all. The individual screw length sizing charts below will help you discover which screws match up from their metric and imperial measurements, so you can ensure that you always use the correct item for your needs.

METRIC – 3mm DiameterIMPERIAL – Gauge Size 4
12mm in length½ an inch in length
16mm in length5/8 of an inch in length
20mm in length¾ of an inch in length
25mm in length1 inch in length
30mm in length1¼ inches in length
40mm in length1 ½ inches in length
METRIC – 3.5mm DiameterIMPERIAL – Gauge Size 6
12mm in length½ an inch in length
16mm in length5/8 of an inch in length
20mm in length¾ of an inch in length
25mm in length1 inch in length
30mm in length1¼ inches in length
40mm in length1 ½ inches in length
METRIC – 4mm DiameterIMPERIAL – Gauge Size 8
12mm in length½ an inch in length
16mm in length5/8 of an inch in length
20mm in length¾ of an inch in length
25mm in length1 inch in length
30mm in length1¼ inches in length
35mm in length1 3/8 inches in length
40mm in length1 ½ inches in length
45mm in length1 ¾ inches in length
50mm in length2 inches in length
60mm in length2 ½ inches in length
70mm in length2 ¾ inches in length
METRIC – 4.5mm DiameterIMPERIAL – Gauge Size 9
25mm in length1 inch in length
30mm in length1¼ inches in length
35mm in length1 3/8 inches in length
40mm in length1 ½ inches in length
45mm in length1 ¾ inches in length
50mm in length2 inches in length
60mm in length2 3/8 inches in length
70mm in length2 ¾ inches in length
75mm in length3 inches in length
METRIC – 5mm DiameterIMPERIAL – Gauge Size 10
25mm in length1 inch in length
30mm in length1¼ inches in length
35mm in length1 3/8 inches in length
40mm in length1 ½ inches in length
45mm in length1 ¾ inches in length
50mm in length2 inches in length
60mm in length2 3/8 inches in length
70mm in length2 ¾ inches in length
75mm in length3 inches in length
80mm in length3 ¼ inches in length
90mm in length3 ½ inches in length
100mm in length4 inches in length
METRIC – 6mm DiameterIMPERIAL – Gauge Size 12
30mm in length1¼ inches in length
40mm in length1 ½ inches in length
50mm in length2 inches in length
60mm in length2 3/8 inches in length
70mm in length2 ¾ inches in length
75mm in length3 inches in length
80mm in length3 ¼ inches in length
90mm in length3 ½ inches in length
100mm in length4 inches in length
110mm in length4 3/8 inches in length
130mm in length5 1/8 inches in length
150mm in length6 inches in length

FAQs

How Do I Know What Screw Size I Need?
Trial and error, usually. You’ll have to try a variety of different sizes, starting with the longest, and assess which size best serves your project.

Does Size Matter?
Of course – a screw that is too small or long for your task is no use at all, and potentially dangerous. If your screw does not disappear fully into its source whilst leaving the ability to tighten, don’t just cut off the end. Remove the screw in question and use an alternative with a shorter length.

Can I Use a Sheet Metal Screw in Wood?
Theoretically yes, but you may be better served using a wood screw due their flexibility.

Can I Use a Wood Screw in Sheet Metal?
No, always use a specialist sheet metal screw in these circumstances. The tensile strength of a wood screw simply cannot compare.

Can I Use the Same Screws for Indoor and Outdoor Use?
Always look for a screw labeled ‘exterior’ of similar if you plan to use it outdoors. These screws will have extra protection against the elements and will not rust or corrode as quickly in the rain.

If I Have a Self-Tapping Screw, Will I Still Need a Screwdriver?
Maybe – it depends on what you are driving the screw into. It’s always advisable to have one on hand.

How Do I Tighten or Loosen a Screw?
Always turn a screw clockwise to tighten it, and anti-clockwise to loosen it again.

How Tight Does a Screw Need to Be?
Very. A loose screw could lead to a loose connection, so you’ll need to ensure that a screw is turned as tightly as you can manage.

My Screw Won’t Tighten – What Now?
If you are absolutely adamant that you have the correct size and style, consider adding a little glue – especially if you are screwing into wood.

Is There a Formula for Screw Sizes to Match Drill Bits?
Unfortunately, nothing simple – it all depends on whether you will be drilling into hard or soft wood, or if you’ll require the use of wall plugs in a foundational part of your home. Keep a variety of screw sizes to hand and work according to the drill bit size that you are happiest using.

Last update on 2020-12-03 / Affiliate links / Images from Amazon Product Advertising API

Sours: https://householdquotes.co.uk/uk-screw-sizes/
Wood Screw Sizes Explained - A Beginners Guide

BS Stainless Limited

THREAD DIAMETER
SizeNearest FractionInchMillimeter
#01/160.061.5
#15/640.071.8
#23/320.082.0
#37/640.092.3
#47/640.112.8
#51/80.123.1
#69/640.133.3
#85/320.164.2
#103/160.194.8
#127/320.215.5
#141/40.246.3

image-6

Sours: https://www.bsstainless.com/american-screw-sizes

Screws no 4

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SHOP TIPS #381 Understanding Machine Screw Sizes tubalcain

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