For a designer/engineer looking for the best connections in an assembly, selection of the correct Fastener is very important.

Cost of the fastener is always insignificant compared to maintenance and liability costs resulting from joint failure.

Design connections using Standards

When components are standardised, they are easier to work with because such components are interchangeable. The product designers should take advantage of the standards available for various types of fasteners.
Almost every possible fastener component has been standardised by international certification agencies and are used by fastener producers. It is very useful to refer them at the design stage itself. Components not specified as above can be considered based upon the manufacturer’s catalogue or datasheet. Refer to the datasheets for all fastener elements provided in these webpages.

Standards define at least one of the following features:

Head shape
Type of thread
Functionally relevant dimensions
Material and strength class
Possible coatings

Many relevant Standards can be downloaded from our downloads section –
Downloads – J C Gupta & Sons (jcfasteners.com)

Selecting the right material

Due to continuous development, there are many more material options for fasteners.
You can download material specifications from this link Fastener Materials

CARBON STEEL

Steel was probably the only material used for fasteners till the development of other options and is still in widespread use due to its versatility and low cost. They generally come with various surface treatments such as zinc or nickel plating to improve corrosion resistance.

STAINLESS STEEL

Stainless Steel is fast becoming the material of choice due to the ability of corrosion resistance and numerous grades available for different applications.

There are various grades of Stainless Steel, each suitable for general or specific applications.

You can download the material specification from the downloads section.

Materials Downloads – J C Gupta & Sons (jcfasteners.com)

Grade A2 AISI-304 SS-1.4301 is the general-purpose material which is the most economical grade that provides reasonably good corrosion resistance and strength.

Grade A4 AISI-316 SS-1.4401 which is also known as Marine or Aerospace or Food or Chemical grade has higher corrosion resistance and longer life.

Now also available is A4-80 which is a higher strength option that improves the usability of SS-316.

There are special grades for specific fastening elements and usage.

SS-1.4122 for locking elements such as Circlips.

SS-1.4532 for Aerospace usage.

SS-316Ti SS-1.4571 for high temperature applications.

AISI-303 for machined components such as dowel pins and standoffs.

AISI-301 SS-1.4310 for spring/flexible elements such as spring pins and spring washers.

400-series SS with higher hardness for self-drilling screws and clinch fasteners (for use in stainless steel sheets).

Bi-Metal – A special fused combination of corrosion resistant stainless steel and carbon steel (to provide the hardness) in self-drilling screws.

Metal-Bonded – SS bonded with EPDM for waterproof washers.

TITANIUM

The unique characteristics of titanium alloys, they have extraordinary corrosion resistance, high tensile strength, low weight and non-magnetic properties.

Ti-Grade2 Commercially Pure C.P. – High corrosion resistance.
This grade of titanium has the highest grade of corrosion resistance. Useful for corrosive environments such as salt water, acids, alkalis, and other industrial chemicals.

Ti-Grade5Ti 6AI-4V – High strength grade.
While not as corrosive resistant as the CP grade, it does offer good corrosive resistance. It offers a higher tensile strength compared to the CP grade.

Check out the options – Titanium Fasteners

BRASS

Noted for corrosion resistance and good conductivity.
Useful for moulding thread inserts – Thread Inserts
Standoffs – Spacers and Standoffs

ALUMINIUM

Aluminium fasteners have come of age. With the availability of special alloys, it has become possible to product strong and durable fasteners from Aluminium.

Advantage of Aluminium

Lightweight; Weighs one third of steel.
Non Magnetic and highly conductive.
High Strength to weight ratio.
Superior corrosion resistance when used correctly; Excellent resistance to acid-base.

Extremely useful for Aerospace applications.

Available as Blind Rivet Nuts – GOEBEL Open End Blind Nuts
Grade – AlMg5 AISI 5056 for high strength.

Hollow Unthreaded Spacers – Unthreaded Spacers
Threaded Standoffs (Spacers) – Spacers and Standoffs
Grade – 6061 T6. Aerospace grade for high strength and strong threads.

Blind Rivets – GOEBEL Blind Rivets
Grade – AlMg5 AISI 5056 for good strength.
Grade – AL99.5 for greater integrity.
Grade – ALMg2.5/3.5 for normal usage

Specialty Rivets – Specialty Blind Rivets
High Strength Structural Rivet – Structural Rivets
Grade – AlMg5 AISI 5056 for high strength.

Self-Clinching Fasteners – Self Clinching Fasteners

Selecting the right screw

Designers should be aware that several options are now available for screwed connections. There is pretty much a specific type of screw for a particular application.

Type of thread

This is highly dependant upon the material and thickness of the base component.

For base materials with low strength consider the following options.

Plastics

JCPlas thread forming screws for plastics. Specially designed screws for strong grip in plastics. JCPlas Thread Forming Screws

Self-Tapping thread inserts. These can provide strong connections and provide for fixing standard machine screws. BAERfix Self Tapping Inserts

Aluminium

Wire thread inserts – Using these can provide a long life to the component. BAERCOIL Thread Inserts and Tools

Self-Tapping Screws. These screws provide a quick and inexpensive installation but suffer from weak thread connections. They are also available with drill points for fast fixing of sheets to a structure. Self-Drilling and Tapping Screws

Wood – Screws for strong connections in wood typically have sharp deeper and wider threads. Expandet Wood Screws

For strong base materials like steel, consider the following options.

Steel

Machine Screws – These are suitable for tapped holes and for using in through holes with matching nuts. Machine Screws, Metal Bolts and Studs
Machine threads are specified differently under various standards. India and most parts of the world follow the ISO Metric standard for thread specification, and it is recommended to use these in your designs. The other popular thread specification is the Unified series or Inch threads. These are specified under ASME and popular for Aerospace products and many electronic applications.

Thread Forming Screws – Also known as Tri-Lobular screws, these eliminate the need to tap the holes. Tri-Lobe Thread Forming Screws for Metal

Type of Head

This element has the largest available options and selection depends upon many factors depending upon the assembly, strength, safety, security and aesthetics etc.

For assemblies requiring a flush level finish

Countersunk head screws. CSK Countersunk Screws, Expandet Wood Screws
JCSlim Low profile screws. JCSlim Ultra Low Profile Screws
Socket head screws with a counter bore hole. Allen Cap SHCS

For assemblies that fix soft materials/thin sheets or have large/irregular holes

Flanged head screws – Flanged Button Head Torx Machine Screws 6-Lobe
JCSlim Large head screws – Ultra Low Profile Wafer Head Laptop Screws

For aesthetic looks and finish

Button Head screws – Button Head Cap Screws – BHCS
Pan Head Screws – Pan Head Screws
JCSlim Low Profile 6-Lobe Screws – Ultra Low Profile Screws Unified Series
Premium 2H Screws – 2H Premium Security Screw
Dome Headed bolts – Dome Bolts

For safety and security

Tamperproof Screws Reusable – Re-Usable Security Screws and Security Nuts
Antitheft permanent screws – Permanent Security Screws

For reducing weight and space of products and components.

JCSlim Low profile screws. JCSlim Ultra Low Profile Screws
JCSlim Thread forming screws for plastics. JCPlas Thread Forming Screws JCSlim
Titanium fasteners. Titanium Fasteners
Aluminium fasteners. Aluminium Fasteners

For tightening from the nut end

Carriage bolts(square neck dome bolts) used mainly for fixing wood to steel. Square Neck Carriage Bolts

Type of drive

Many different drive styles have been developed over the years, each new innovation providing some benefits.

Hex drive

Slotted drive – Among the oldest designs. Known for its simplicity. Can be driven with a standard flat blade screwdriver. Slotted Machine Screws

Cross recessed (Phillips) drive – Versatile and widely used. Suffers from Cam-out and quicker wear. Phillips Machine Screws

Hex Socket (Allen) drive – Good for high torque. Narrow head facilitates use within machinery. Allen Screws or Hex Socket Screws

6-Lobe (Torx) drive – An improved version of the hex socket drive providing higher reliability. Torx Machine Screws 6-Lobe

Security drives – For tamper/theft resistant installations.
Pin-Hex – Pin-Hex Machine Security Screw
6-Lobe-Pin – Pin-Torx Machine Security Screw
5-Lobe-Pin (Premium) – 5-Lobe Pin Premium Security Screws
2H drive – 2H Premium Security Screw
One-way (Clutch) – OneWay Security Screws
System-Zero (Premium) external drive – System Zero Premium Security Screws
Permanent Shear Bolts – TWIST Shear Bolts)

Screw length and thread engagement

It is pertinent to note that planning the correct bolt/screw length provides for a joint that ensures safety and saves space, weight and cost.
Thread Protrusion of a bolted assembly

Selecting the optimum thread engagement length is important to make a strong connection for a component with a tapped hole. Screw Thread Engagement

Mechanical Properties

Every assembly comes with different requirements with regards to strength of the joint and required mechanical properties.

Careful consideration should be given to the following characteristics while selecting the right fastener.

Tensile Load
In general, most stainless steel screws are available in 70 strength grade with 80 grade feasible in some types and sizes.
ISO 3506.

Hardness
This property is useful for higher life of threaded connections for repeated removals.

Shear Strength
Assemblies which are subject to shear loads should be provided with suitable fasteners. Higher diameters take higher Shear loads in general.

Torque
The most important property for any fastener connection.
Pay close attention to recommended torque before installing screws.
Do not overtighten. Keep within the suggested Torque values. Using a Torque control tool is recommended.
Download Torque Guide.