As the trend toward electrification and energy efficiency accelerates, industries such as automotive, electronics, and lighting, among others, are increasing their demand for lightweight materials. Lightweight components enhance performance and efficiency while reducing resource consumption and emissions. Die casting makes it possible to produce strong, lightweight components with precise geometry, but assembling these parts introduces unique challenges.

Challenges in assembling die‑cast parts

Assembling die‑cast components can be challenging because of how screw holes are formed during the casting process. In die casting, holes are created by a core pin with a small draft angle (α), so when molten metal flows around the pin, the resulting hole reproduces its slightly conical shape rather than being perfectly cylindrical. (Fig.1)

Fig 1. Screw hole with draft angle

During screw installation, the tight, conical hole generates high pressure and friction, which causes the aluminum to adhere to the screw threads. (Fig 2)

Fig 2. Screw threads with adhered aluminum

Blockage and thread stripping during installation​

When a screw is inserted into a tapered or conical screw hole, uneven thread engagement occurs along the hole depth: the upper part of the hole has low engagement, while the lower part has higher engagement. This uneven load distribution can cause assembly issues:

  • Thread Stripping: Limited engagement at the upper part reduces resistance to stripping and loosening.
  • Blockage: High friction at the tighter zone of the hole leads to screw blockage and galling (cold welding).


These assembly issues can lead to line stoppages, costly rework, and production delays.

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Inconsistent draft angles in die‑cast hole​

Core pins wear down over time due to erosion from molten metal flow, thermal cycling, and abrasion. Therefore, different pins may wear at different rates and the draft angles can vary widely, with parts exceeding 2º or becoming inconsistent even within the same batch.

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Typical workaround approaches - but ineffective

Drilling (and sometimes tapping) the holes 
Increases assembly cost due to the additional drilling and tapping operations.​​

Oversized conical holes
Increases assembly cost due to the additional drilling and tapping operations.​​

Applying extra lubricant on the screws
Increases assembly cost due to the additional drilling and tapping operations.​​

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The solution for fast, smooth assembly in die-cast parts

At CELO, we provide fastening solutions specially designed for die-cast assemblies and tailored to each application. They help to:

Minimize the risk of screw blockage

Eliminate drilling and tapping operations, reducing the total assembly cost​

Reduce the risk of thread stripping

Increase pull-out strength and resistance to vibration loosening​

Provide stable tightening torque

Provide reliable clamping force​

In addition, we offer screw solutions that optimize assembly time by reducing the number of turns required to secure the joint, resulting in a faster and more efficient assembly process.