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A manufacturer of an automotive valve body assembly turned to Spirol Industries after needing to locate the upper and lower valve bodies during sub-assembly.

The manufacturer wanted to reduce hole preparation time, reduce the weight of assembly, lower installation forces and simplify the assembly/part feeding process within the plant.

Spirol’s coiled spring pins were supplied for the solution.

The assembly consists of two die-cast aluminium valve bodies (upper and lower).

These bodies needed to be ’pinned’ in two places 180deg from each other.

The manufacture also wanted to utilise locating pins during final assembly to locate the transmission case.

The total cost of the assembly was also being monitored very closely.

Initially, machined solid pins and slotted spring pins were trialled, but could not provide the lowest installed total cost and were also difficult to install.

The solid pin required a very precise hole, increased the overall assembly weight, had a higher installation force – and was more expensive overall.

The slotted spring pin did not provide precise enough critical alignment to the finished transmission case and could not be automatically fed due to fact that this type of pin is not very straight and the imperfect chamfers on the ends of the pins made it difficult to start the pin during installation.

Spirol Industries said that its light-duty coiled spring pins offered the optimum balance of strength and flexibility that exceeded all of the performance requirements for this particular application at the lowest installed cost.

Evaluation of the assembly revealed that a pin could be fixed in the lower valve body, align the upper body and provide a clearance fit in the transmission case for ease of manual assembly.

As coiled spring pins use the same nominal hole size configurations (except with a wider overall tolerance) as standard machined solid pins and slotted spring pins, Spirol’s solution was implemented.

Coiled pins are designed in such a way that their pre-installed diameter is larger than the recommended hole.

The diameter is compressed as the coiled spring pin is inserted.

Once installed, it retains itself by exerting constant radial force against the hole wall as it attempts to recover back to its pre-installed diameter.

This flexibility enables the coiled pin to absorb the widest range of manufacturing tolerances of any other press fit pin while simultaneously providing the required retention force.

The clean, cut square ends of the coiled pin provide a generous lead-in for insertion of the pin as well as for assisting in the alignment of mating components.

The combination of the coiled pin’s straightness, its square ends, concentric chamfers and gap-free configuration makes it ideal for automatic feeding and assembly.

Its lightweight construction achieved the weight reduction goal, as well as lower installation forces.

Spirol Industries

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