Category: Screws

A Retrospect to the Standard Screw Sizes

The use of fasteners has grown extensively worldwide, increasing the need of coming up with standard screw sizes. Standardization prevents the use of improper screws, and ensures screws are compatible with the materials being used and are appropriate for the project at hand. Screw dimensions include the driver type — such as flat, Phillips or hex — length, shank diameter and threads per inch.

The demand for fasteners has extensively grown globally, especially in the world of online marketing. This growing demand has simultaneously increased the requirement for standard sizing of these hardware supplies.

By classification, the hassle of each time landing up with screws with different patterns and lengths can be greatly avoided. This even ensures that these rivets become comme il faut with the materials, being used in the construction or any build-up project. The various dimensions of these fasteners demand ofr use of various type of screwdrives, such as hex, Phillips, flat determining the shank diameter, length and threads per inch.

Screw’s numbering system

when standardization was done, the screws were put into 2 distinct numbering systems; the metric and U.S numbering systems. The metric measuring system lists out the diameter of these rivets in millimeters first and then secondly in thread pitch. The examples for this category include 6 mm x 1.0, 4 mm x 0.7, 5 mm x 0.8 etc. The U.S stadnard measurement system inlcudes screw with diameter sizes as 0, 1, 2 ,3, 4, 5, 6, 7, 8, 9, 10, 12, 14 and 16 and even in fractional sizes ranging from  1/4″ to 2″ in 1/16″. This is followed by threads and dash per inch falling between 6 and 80.

Diameter of screws

The first number metioned in the size charts for diameter must match the inner diamter of the washers ad nuts applied to them. The diameter of the rivet is measured at the shaft, just below the screw head. The diamter size ranging from 0 to 16 is declared by the American Society of Mechanical Engineers, thereby enabling the hardware sizing system to be extensively adopted worldwide. This kind of measurement made in standard U.S fractions was recently added and countries outside of America  are also seen following this standardization.

Length of screws

While the pan head screw’s length is measured from the flat end of its round head to its tip, the length of the flat head screws measure from the top of the head to the tip of the rivet.

The length is the third item typically listed in the size chart and is identified by an ‘x’ symbol. For instance, a #8-20 x 3/4″ screw features 20 threads per inch and a shaft measuring 3/4″ in length and a 5/8-24 x 1″ screw has a diameter of 5/8″, 24 threads per inch and has a 1″ shaft.

There are some fasteners, which are measured as per the threads per inch sizing, execpt for their length and diameter such as 5/16 x 1/2″ and #10 x 1″

Threading of screws

This kind of measurement is at number 2 in the chart of standard screw sizes. The hyphen refers to the number of threads of screw shaft per inch. For e.g. a 1/4-28 sized screw has diameter of 1/4″ along-with 28 threads per inch and a #6-32 screw has 32 threads per inch on its shaft.

Salient Features of Clutch Head Screws

If you happen to see some kind of odd bow-tie shaped screw slots on your door or window pane, you’ve probably discovered the clutch head screws.  Such fasteners were extensively used in the auto industry from the 1940s through the 1960s. In 1970s, few of these screws also paved their way into travel trailer manufacturing industries as well.

10X High security clutch screws

Clutch head screws are also known as One Way Screws and ‘Security Screws‘. These specially designed fasteners are used for lasting installations. These are easy to use and can be installed using a normal screwdriver. The head of such kind of fastener features a normal drive and slanted rear face, which prevents the screwdriver from applying torque when trying to loosen these fasteners.

Once implanted, these rivets require typical drilling application for removal from the holes. However, you can even fetch for a special kind of driver bit to undo them.

Steel Clutch Head screws

In order to unscrew these rivers, you’re required to use a screwdriver bit of the same shape and size. The clutch head one way screws can be unscrewed in the clockwise direction by using a standard slotted screwdriver. This drive system was probably the worlds first security recess.

Unique Design

This unique feature enables such screws to be tamper-proof, thereby enhancing the security of your house and lessening the risk of robbery and making it impossible for the intruders to tamper the screws. Due to their unique design, there are even ideal for higher torque applications.

Clutch head with a hole for screw Driver

Thus, these fasteners are also referred as Jail Head. They are usually self-tappers and are used in applications jail cell hinges and even in domestic window locks and exposed door lock screws.


Standard Clutch Head

Standard Clutch Heads of screws

The clutch head screws are usually of two types: type A and type G. The type A is also known as a standard clutch and usually resembles a bow tie. And the type G resembles a butterfly.

Type G Clutch Head of a screw

These are zinc plated hardened steel and cannot be removed once they are installed. Besides, the countersunk clutch head screws can only be opened by a flat head screw driver


The type A screws were widely used earlier and were commonly seen in 1940s’GM automobiles, including trucks and buses. And the type G rivets are commonly used in the construction of mobile homes and recreational vehicles. You can even find them in your windows and doors, if they’re installed with some odd bow-tie shaped screw slots.

Special features of Clutch Head screws

These are ideal for

  • Public access wooden windows & doors
  • Seating & fencing
  • Prison fittings & fixtures
  • School & college fixings & fixtures
  • Also used in timber applications

Added Benefits

A police survey shows that around 30% of the intruders gain access to the houses through windows. Therefore, it’s utmost necessary to keep your windows secured.

Key-Rex Shape Security fastner

Beat the thieves with the clutch head screws!  

Their ‘one way’ design lets you fasten these screws with an ordinary Slotted screwdriver, but unscrewing them is virtually impossible. Hence, these can be of great help, as their unique features make it impossible for them to be unscrewed using a driver, instead a driller is required to undo them.

There’s another kind of screw known as A2 clutch head round wood screws.

Self tapper A2 Clutch Head round Wood screws

These fasteners are also known as Clutchless Screws and are made up of A2 stainless Steel.

These types of hardened steel self tapping screws can be used with various materials including wood, plastic and as a self tapping screw.


5 Inch construction screw

  • These fasteners are mostly used by the police and councils to secure number plates
  • Construction Security Screws
  • Sign Security

Now Get Rid of Squeaky Floor with Plywood Screws

Plywood screws, which are also known as chipboard screws are self-tapping screws, featuring thin shaft and coarse threads. These fasteners are made up of either wood dust or wood chips and resin, and as the name suggests, these screws are mainly in plywood and other soft wood surfaces.

These rivets are made to clinch this composite surface, so as to withstand loosening. The screws firmly hold either two plywood or any chipboard to other materials, say natural wood.

Apart from wooden works, these screws are highly recommended for squeaky floors as well. Recently one of our esteemed clients faced an issue with pressboard sub-flooring in his 20 years old house. While his upstairs flooring was creaking under the carpet, the downstairs floors jolt the entire house whenever stepped on promptly.

His main concern was to stop those high-pitched annoying sound and if he should go for another layer of plywood over the existing flooring? He was also interested in replacing the entire floor.

Playwood Screws for wood floors

So, this is what we had suggested him. Read on!

Instead of spending huge bucks in replacing the entire flooring, you can always go for an additional layer of plywood, which will definitely resolve all those issues. We highly recommend you to go for thicker material, as thicker the size would be, the degree of sound transmission would be reduced to more extent.

And yes, it’s always possible to fasten the existing wooden surface with the new layering. You’ll have to mark out the old nailing patterns, which should be in a gap of minimum 16 inches. Our aim should be enabling every new fastener with a supporting beam. By doing this, the squeaks will be reduced to a great extent and will even laminate properly the new layers along-with the base.

The plywood screws are the most ideal supplies required for fastening and you can even go for gluing, thereby strengthening the grip even more.

Different Sizes Of Play Wood Screws

In the meanwhile, do not forget about the sap, which pulls this surface up. So, better fasten it with those screws.

And do not try compromising with the quality of the screws, as this is definitely not a place to think about cost-cutting. So purchase the plywood screws in ample quantity and insert screw at every 4-6 inches of gap at the seams and at every 6-8 inches of gap in the field.

This is indeed an effective method, giving away long lasting results.

Much better looking wood floor with playwood screws

If your plywood is of 5-8 inches thick then you should consider those screws, which are at least 2 and 1/2 inches long, so that they can get a nice grip. However be warned that you don’t have any radiant heating line or plumbing beneath this surface.

We suggest you to go for an half inch plywood for the layering and you can even bowl over the seams from the existing surface. You can go cheap on the facings for the plywood to save from the recent hike in their pricing. For instance, you can go for CCX PTS, which exactly works as the ‘A’ grade material or you can even opt for OSB, which works well under the carpet.

The rooms with carpets need a little adjustment, as you would have to manage with the closets and swing doors for proper installation. You need to build a carpet shelf by raising the level of the carpeted areas.

But the major problem arises in areas, where you’re thinking of installing vinyl or linoleum flooring. For this, you’ll need a third layer of chipboard or particle board and so also the have to determine the size and thickness of plywood screws.

Not to mention, stairs are another nightmare. You can easily face trip hazards and in order to prevent this, you should confirm that the building code should have a minimum gap of at least 3-8 inches between the stairs, but the height should not exceed above 8.