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PT Type DG
The PT Type DG is a direct screw fastener for use in light alloys.
The design incorporates many unique features which provide designers with a really effective direct screw fixing for these materials.
The profiled thread root gives low installation torque whilst the special thread form provides high stripping torque.
Advantages
- Thread forming - No debris
- Reliable & easy installation into punched, drilled, extruded & molded holes
- Reusability of screw
Design Features
Special Profiled Root
The PT Type Screw is shaped to allow material flow, aiding in smooth formation and reduced stress.
- Reduces stress
- Allows material to flow during thread forming
- Reduces installation torque
- Increases pull-out load
Special Shaped Tooth
It provides low installation torque in light alloys while maintaining high stripping torque for reliability.
- Reduces radial stress
- Maximum surface bearing area
- High stripping torque
- High clamping force
- High back-off torque
PT Type DG Design Guide
Soft materials = ≤ 50 vpn
Medium soft materials = 51 to 75 vpn
Hard materials = 76 to 100 vpn
For specific application advice, contact PSM.
Hole & Boss Dimensions
- Use a slight taper (~1° inclusive) in the hole for smooth insertion.
- Optimize hole diameter at the mid-penetration point for effective thread forming.
- Minimum boss diameter is generally about 2.5 × d (nominal thread diameter).
- Recommended screw penetration ranges between 1.5 × d and 2.5 × d depending on material hardness.
Material & Load Factors
- For soft alloy castings or thin walls, ensure the boss and surrounding geometry can withstand stresses during installation.
- In plastic regions, include ribs or reinforcements to prevent deformation.
Installation & Torque Control
- Drive the screw gradually to allow proper thread forming without jamming.
- Avoid over-torquing to prevent stripping or cracking.
- Use torque-controlled drivers at recommended speeds to reduce heating or damage.
Hybrid Assembly Tips
- For plastic-metal assemblies, sequence screw insertion to suit structural needs.
- Validate that forming in one material doesn’t compromise performance in the other.
PT Type DG Dimensions
How to Specify
Applications & Advantages
PT Type DG is ideal for hybrid assemblies such as lighting housings, enclosures with metal frames and plastic covers, and brackets attached to die castings. Its advantages include:
- Unified fastening solution across metal and plastic
- Simplified inventory and assembly
- Strong thread performance in light alloy
- Resistance to vibration and relaxation
- Reduction in part count and assembly errors
Enhance Your Assembly with Our Precision PT Type DG Screws
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Frequently Asked Questions About PT Type DG Series Screws
What is the PSM PT Type DG Series screw?
The PSM PT Type DG Series (WN15) is a dual-material direct screw fixing engineered to work in both light metal alloys and high-filled thermoplastics with a single screw design. Its special profiled root reduces installation torque while the shaped tooth profile provides high stripping torque, making it ideal for hybrid plastic-metal assemblies.
What does "DG" stand for in PT Type DG?
“DG” refers to the screw’s dual-geometry thread design, which enables it to form effective threads in both light alloys (such as aluminium and zinc die-castings) and high-filled thermoplastics in the same assembly. This eliminates the need to specify separate screws for metal and plastic components in hybrid structures.
What is the WN15 standard for PT Type DG screws?
WN15 (Werksnorm 15) is the industry standard governing the thread geometry, dimensional tolerances, and performance requirements for PT Type DG direct screw fixings. It defines a differential thread profile optimised for dual-material use in both light metal alloys and high-filled plastics. PSM manufactures to WN15 under ISO 9001:2015 certification.
What is the difference between PT Type DG (WN15) and the standard PT Series (WN14)?
The PT Series (WN14) is optimised for standard thermoplastics and light alloys separately. The PT Type DG (WN15) uses a dual-geometry thread profile specifically engineered to perform in both light alloys and high-filled plastics within the same assembly — delivering low installation torque via its profiled root and high stripping torque via its shaped tooth.
Can PT Type DG screws be used in hybrid plastic-metal assemblies?
Yes, hybrid assemblies are the PT Type DG’s primary application. It is engineered to fasten simultaneously or sequentially into both a light alloy component (such as an aluminium die-cast frame) and a high-filled plastic component (such as a glass-filled nylon cover), using one unified screw specification. This simplifies inventory and reduces assembly complexity.