Fasteners by application & material

Fasteners for wood

Wood is a living material - it expands, contracts, absorbs moisture and releases it again. This is why timber construction requires special fasteners that can withstand these dynamic properties. Items such as coarse-thread screws ensure a secure hold, while disc head screws with a wide bearing surface prevent pull-through and distribute forces optimally. For load-bearing structures such as roof trusses, connecting elements approved by the building authorities as well as beam shoes, angles and flat connectors made of galvanised steel are indispensable.

Typical products:

• plate head screws with ETA approval for load-bearing timber connections
• Beam shoes, angle connectors und perforated plates for frame constructions
• Chipboard screws with milling ribs for a clean and secure fit

Steel fasteners

Steel fasteners are indispensable in mechanical and plant engineering and for statically loaded structures. They have to withstand extreme forces - whether in tension, compression or shear. The decisive factor is the strength class: while 8.8 screws are sufficient for standard applications, screws of classes 10.9 or 12.9 are used for safety-relevant applications. When supplemented with locking elements such as tension discs, the result is heavy-duty connections that function permanently even in the event of vibrations. Precise process steps and high quality requirements are crucial in the manufacture of steel fasteners in order to ensure the reliability and durability of the products.

Typical products:

• Hexagon head screws, such as DIN 933 / ISO 4017 for universal machine use
• Hexagon socket head screws, such as DIN 912 / ISO 4762 with hexagon socket for precise screw connections
• Spring washers and split pins to prevent self-loosening
• Dowel pins and bolts for precise alignment and guidance

Stainless steel fasteners

In many industries, corrosion protection is not only a convenience factor, but also a safety factor. Stainless steel fasteners can withstand moisture, aggressive media and temperature fluctuations - without any loss of strength. A2 stainless steel is suitable for general outdoor areas, while A4 stainless steel is particularly resistant to chlorinated air, salt water and chemical influences. These materials are indispensable in food technology, medical technology, façade construction and outdoor products. In combination with tested locknuts, washers and material certificates, a durable and standard-compliant connection is created.

Typical products:

• Stainless steel screws A2 / A4 for corrosive environments
• Locknuts with clamping part for vibration-proof seating
  Threaded rods and pieces
• Threaded rods and pieces
• Stainless steel fasteners with 3.1 certificate in accordance with DIN EN 10204

HV fittings - Special fasteners for steel construction

Automotive fasteners

The automotive industry places the highest demands on quality, process capability and traceability. Fasteners must be mechanically resilient, capable of automated processing and documented testing. High-strength screws of classes 10.9 and 12.9 are used for chassis components, steering and engine suspensions. Fastening solutions with integrated screw locking, plastic clips or special coatings are also standard. The ability to be supplied in accordance with VDA standards and integration into logistics systems play a central role in the products. Close co-operation with manufacturers and with our application technology is crucial in order to develop innovative solutions that meet the increasing demands of the automotive industry.

Typical products:

• High-strength hexagon head screws for load-bearing body elements
• Clip and quick-connect systems for interior panelling
• Sealing screws with integrated seal for the engine compartment and fuel tank
• Drawing-based special parts with traceability certificate

Sheet metal connections & fasteners for thin materials

Thin sheets and profile materials have special requirements: The connection must hold without deforming or damaging the material. Specially designed fastening elements such as self-tapping screws with a drill point, blind rivets or press-in nuts are used here. These enable secure assembly - often even on one side - and are typically used in housing technology, apparatus engineering, air conditioning technology or lightweight constructions. When selecting or installing fasteners for thin materials, problems such as material deformation or insufficient holding force can occur, which is why careful planning is essential.

Typical products:

• Self-tapping screws with self-drilling tip for quick installation without pre-drilling
• Blind rivets for stable connections with access from one side
• Press-in nuts for strong threaded connections in thin sheet metal
• Welding studs for permanent fixing on conductive materials

Plastic fasteners

Plastic fasteners are used where weight is reduced, electrical insulation is guaranteed or chemical resistance is required - for example in electronics, plant engineering or medical technology. Fasteners made of polyamide and engineering plastics offer lightweight construction, corrosion resistance and easy assembly. Many products can be assembled without tools and are suitable for delicate components and sensitive surfaces. Costs play an important role in the selection of plastic fasteners, as they have a significant influence on cost-effectiveness and the decision in favour of certain solutions.

Typical products:

• Polyamide screws and nuts for insulating connections
• Washers, threaded bolts and grub screws
• Cap nuts and wing nuts

How to make the right choice: The right product for your application - piece by piece

Material of the components to be joined

A key selection criterion for the product is the material of the components that are to be connected. Each material has specific requirements for the connection:

• Wood requires screws with a coarse thread, such as disc head screws or wood connectors. These provide a strong hold in the fibrous material and ensure a secure, load-bearing connection.
• Sheet metal and thin-walled metal parts require special solutions such as press-fit fasteners, blind rivets or bolts, which can be reliably installed even with limited material thickness.
• Plastic parts should be connected with plastic fasteners or non-conductive materials. This prevents material stresses and ensures electrical insulation.

Mechanical load on the connection

The recommended design differs depending on the forces to which the connection will later be subjected:

• Tensile loads (e.g. for suspensions or load-bearing components) require high-strength screws with defined strength classes (e.g. 10.9 or 12.9) to ensure maximum safety.
• Shear loads (e.g. with overlapping metal sheets) can be optimally absorbed by dowel pins or bolts, as they are designed to withstand shear forces.
• Vibration loads, which often occur in vehicle construction or machinery, require locking elements such as spring washers or screw locking devices with adhesives.

Environmental influences and place of use

The environment in which the fastener is used also has a major influence on the choice of material and surface treatment:

• In normal indoor areas, galvanised steel is usually sufficient.
• For outdoor applications with moisture or temperature fluctuations, the use of A2 stainless steel is recommended.
• In particularly aggressive environments - such as near the coast, in swimming pools or in the chemical industry – A4 stainless steel is ideal, as it is resistant to chlorides and acids.
• For electronic applications or circuits, connecting elements made of non-conductive plastics are required to prevent faults and short circuits.

Requirements for re-solvability

Whether a connection can be loosened again or should hold permanently is often a decisive criterion in the design:

• Screw connections with and without nuts are detachable and enable maintenance, repair or replacement of components.
• Rivets or welded connections such as bolts, on the other hand, create a permanent, non-destructively detachable connection - the ideal product for economical series assembly or areas that are difficult to access.
• Snap and click connections offer quick, tool-free assembly, but are often only reusable to a limited extent.

Assembly conditions on site

The spatial and logistical conditions during installation also determine which product is best suited to the application.

• If access to the connection is only possible from one side - for example with closed housings or pipes - blind rivets or press-in nuts are used.
• IIn visible areas such as housings or displays, the screw should also fulfil visual requirements - e.g. with a decorative head shape such as lens head or countersunk head..
• In tight installation spaces, fasteners with a low overall height, such as flat-head screws or combination screws with an integrated washer, are particularly advantageous.

Frequently asked questions about fasteners

What is the difference between A2 and A4 stainless steel for fasteners?

A2 stainless steel is corrosion-resistant and is suitable for indoor and moderately stressed outdoor areas. A4 stainless steel offers additional protection against aggressive media such as chlorides and acids and is therefore used in the chemical industry or coastal regions.

How long can fasteners be stored?

If stored correctly (dry, dust-free, temperature-stable), fasteners made of steel, stainless steel or plastic can be kept for several years. Galvanised screws should be protected from high humidity, plastic parts from UV radiation and extreme temperatures.

How do you recognise the strength class of a screw?

The strength class is usually stamped on the screw head. Classes such as 8.8, 10.9 or 12.9 provide information about tensile strength and load-bearing capacity.

Are there fasteners with an environmentally friendly coating?

Yes, e.g. with zinc flake technology without hexavalent chromium (Cr(VI)). These coatings are REACH-compliant, environmentally friendly and offer a high level of corrosion protection.

Which test certificates are available for fasteners?

Keller & Kalmbach can provide test certificates in accordance with DIN EN 10204 on request, e.g. factory certificate 2.2 and acceptance test certificate 3.1, for traceability and conformity to standards.