Measuring Socket Cap Head Self Tapping Screws THREAD Diameter

[Lionelgee]

Hello All,

I need to buy some Socket Cap Head Self-Tapping Screws that are twice as long as what came fitted to my car.

I tracked down different suppliers in Australia. One supplier included a dimensions diagram however it is unclear what point they are suggesting to measure as a diameter to order. One of the dimension lines is on the last tapered thread of the screw and the second dimension line is on the first horizontal and parallel thread that extends along the majority of the screw's length.

For self-tapping screws do you measure the top of the thread where the sides remain parallel (Red) ; or the internal un-threaded shank the internal diameter of the screw (blue)?

I have added another diagram that I hope explains what diameter the manufacturer's are referring to

Kind regards
Lionel

[p38arover]

The title says head diameter. Do you mean thread diameter?

[Lionelgee]

The title says head diameter. Do you mean thread diameter?

Hello P38 Rover,

Well spotted Ron. Yes Thread Diameter if this is the "d" dimension in the diagram in the earlier post.

Oops - I copied and pasted the title and the manufacturer duplicates the word "head" a couple of times in their description.

I will change the subject line too.

Kind regards
Lionel

[W&KO]

are these sold as a gauge I.e. 14g?

I’d say its measured across parallel section.

[Slunnie]

That diagram is indicating the major diameter, so if you wanted the screw to drop through a hole but be stopped by the head, that’s the dia you would drill. The diameter at the tops of the screw threads on the untapered section.

[trout1105]

With most self tappers the drill size needed will be written on the packaging, If it isn't then Always start small and work up until you find the correct size drill you need [thumbsupbig]
The diameter measurement you are looking for is for the "Shank" or body of the screw, Not counting the thread itself

[scarry]

are these sold as a gauge I.e. 14g?

I’d say its measured across parallel section.

Yes they generally are,10 guage,12 guage,etc.

But there are also huge differences in the screws,head types,thread types,and different tip types and styles.

Some are designed for timber,others metal of different sizes,and some go into nylon or plastic.

[Lionelgee]

Hello All,

The Socket Cap Head Self-Tapping Screw is from the dashboard of my car. I am fitting a new bracket to hold a reverse camera. The current screws are going to be too short to hold the new bracket.

So I am trying to work back from a screw's dimensions to be able to find out what the packaging description is. This information will allow me to buy longer screws that have a matching head. I would like the new longer screws to blend in with the rest of the dash.

Kind regards
Lionel

[W&KO]

Just measured what I have laying around.

8-10G Cross Tip Wood 2.7mm
8G Cross Tip Sheet Metal 3.1mm
14G Cross Tip Sheet Metal 4.7mm
10G Hex Drive Metal Drill Screw 3.6mm
12G Hex Drive Timber Screw 3.8mm

All measured on the parallel section at the bottom of thread.