Self-tapping fasteners

EJOT DELTA PT® screw

Strong connections for lightweight construction. With EJOT DELTA PT®, the self-tapping fasteners for thermoplastic materials.

 

Reliable plastic threaded fasteners

EJOT DELTA PT® is a thread-forming screw for plastics and is especially suitable for thermoplastic materials.

The EJOT DELTA PT® screw is a development of the PT screw, and the result of years of hands-on experience of screw fastening in thermoplastic materials. As a rugged fastener it delivers superb performance, even under extreme conditions of use.

Method / principle

The special thread geometry, which is the result of a thorough analysis of material displacement during thread-forming, allows the formed plastic material to flow off in an optimal manner.

Applications

Self-tapping fasteners for plastics are ideal for thin-walled, flat construction methods. Their use can lead to material savings and shorter injection moulding cycle times. Taking into account the overall fastening costs for a component, self-tapping fasteners provide significant potential for savings.

Product benefits
  • Significantly longer joint life
  • Optimised material flow during screw fastening
  • Good vibration resistance
  • High tensile strength and torsional resistance
  • Made of heat-treated steel PT 10

Product benefits

There are many good reasons for using our products.

Strength and options.
Point by point.

Minimal radial stress

Small flank angles reduce radial stress, allowing for thin-walled construction methods.

Secure hold

A perfect fit, through optimised material flow during assembly.

Self-locking effect in thread

The optimised pitch minimises the possibility of the screw working loose.

Extended life

Quick to install but very durable, thanks to the use of heat-treated steel PT 10.

High tensile strength and torsional resistance

The enlarged core cross-section increases the strength of the screw so that high preload forces and tightening torques can be achieved even in high-strength thermoplastics.

Weight reduction

In lightweight construction every gram counts. In contrast to conventional joints, shorter screws and/or smaller diameters can be used.

Cost-effective

Lower inventory costs through the use of standard parts.

Geometry

 

Core cross section

  • High tensile and torsional strength due to large core cross section
EJOT DELTA PT® screw core cross section

EJOT DELTA PT® screw

Core cross section

 

Thread flanks with formed nut material

  • Optimal flow of the formed plastic
  • High self-locking against loosening
  • High thread overlap even with small screw-in depth
  • Largely low-damage material discharge
Thread flanks Nut material of the EJOT DELTA PT® screw

EJOT DELTA PT® screw

Thread flanks nut material

 

Thread flanks in detail

  • Thread geometry suitable for plastics
  • Balanced ratio of preload force to surface pressure
  • High preload forces and tightening torques possible
  • High self-locking due to thread pitch suitable for plastic
  • Large flank overlap enables low surface pressure (PFL). As a result, the stress reduction in the polymer remains low and the residual prestressing force of the joint is maximized.
Thread flanks of the EJOT DELTA PT® screw

EJOT DELTA PT® screw

Thread flanks

 

Thread flank geometry in cross-section

  • Low radial expansion due to 20°/30° flank angle
  • The 140° transition angle from the thread tooth to the core diameter results in a high bending stiffness in the thread tooth
  • Thin-walled tube design possible. This saves material and allows lightweight construction aspects to be realized. Reduced injection molding cycles represent an additional process optimization.
Thread flank geometry in cross-section of the EJOT DELTA PT® screw

EJOT DELTA PT® screw

Thread flank geometry in cross-section

Assembly

 

Easy assembly

The assembly of EJOT DELTA PT® screws is done with state-of-the-art screwing machines. As visible in pictures 1 to 3 the screw is positioned and screwed in. The screwdriving unit switches off at a given tightening torque.
The recommended screwing speed is 500 rpm. To save assembly time, it can be increased to up to 1,000 rpm for engineering and high-performance plastics.

The assembly of the EJOT Delta PT<sup>®</sup> starts by positioning and screwing in.

1. Positioning

The assembly starts by positioning and screwing in.

​​​​​​​
The closed tube geometry of the EJOT DLTA PT<sup>®</sup> ensures a continuously increasing torque.

2. Thread forming

The closed tube geometry ensures a continuously increasing torque.

If the head support of the EJOT DELTA PT<sup>®</sup> is hit, the pretensioning force increases exponentially until the recommended automatic switch-off.

3. Final tightening

If the headrest is reached, the preload force increases exponentially until the recommended automatic switch-off.

Product variants

 

EJOT DELTA PT® for thermoplastics

The design of the screw-in tube in conjunction with the clamping part has a decisive influence on the durability of the screw connection. The EJOT DELTA PT® thread was developed especially for direct screwing of thermoplastics.
The combination of special thread pitch and formed flank angle enables the realisation of a particularly efficient connection.

EJOT DELTA PT® screw for thermoplastics

EJOT DELTA PT® screw for thermoplastics

 

EJOT DELTA PT® DS for thermoset plastics

The EJOT DELTA PT® screw enables reliable connections in the field of direct screwing in plastics. Some constructions require thermosetting plastics which, due to their hardness and brittleness, have special demands on direct screwing.
Modified thread flanks are required to enable direct screwing into these particularly demanding materials.
With the thread form DS (DuroSet) EJOT has responded to these demanding conditions. The EJOT DELTA PT® DS screw has special grooves on the proven EJOT DELTA PT® thread geometry, which significantly support the cutting process in the nut thread. These grooves are particularly pronounced at the screw tip and run out towards the screw head. The thread forming zone enables a low insertion torque and a high overtorque.

EJOT DELTA PT® DS screw for thermosetting plastics

EJOT DELTA PT® DS screw for thermosetting plastics

 

In order to achieve the highest possible torques with these hard thermosets, a screw-in depth of 2.5 x d is recommended.
If both thermoplastic and thermoset components are to be screwed together in assembly and identical screw dimensions are to be used for cost reasons, the DELTA PT® DS screw, with a slightly lower torque level, can also be used for thermoplastic components.
The EJOT APPLITEC is at your disposal for component tests.

Modified thread flanks of the EJOT DELTA PT® DS screw

Modified thread flanks of the EJOT DELTA PT® DS screw

 

EJOT DELTA PT® P for standard thermoplastics

When it comes to designing components for direct screwing of thermoplastics with steel screws, it frequently occurs that the strength of the screw-in material is significantly lower than the screw material itself, especially with standard thermoplastics.
For the EJOT DELTA PT® P screw the high performance plastic PPA GF50 is used as screw material. This enables a self-tapping screwing into standard thermoplastics. Thus a light and electrically or thermally insulating screw connection can be realised.

EJOT DELTA PT® P screw for standard thermoplastics

EJOT DELTA PT® P screw for standard thermoplastics

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