Design Pneumatic Shrinker/Stretcher - Hype Classics + Customs
Matt from Hype Customs and I first connected through some outreach. As we discussed how we might work together, the concept for a handheld pneumatic shrinker/stretcher began to take shape. Matt had been thinking about the idea for a long time but hadn't yet had the resources to bring it to life through design and manufacturing. A traditional shrinker/stretcher is a foot-operated machine where the user feeds the sheet metal into the jaws by hand while actuating the mechanism with a foot pedal. This works well for loose pieces of sheet metal, but becomes impractical when working directly on a vehicle where access is limited and large panels cannot easily be positioned in the machine. Our goal was to create a handheld version that could be used just as effectively on loose pieces as it could directly on the vehicle, allowing metal to be shrunk or stretched wherever it was needed.
We started with an existing pneumatic tool and looked at how it could be adapted for this application. The tool already had a threaded shaft, which helped define the thread size and overall dimensions for the jaws. It was also capable of providing a controlled amount of force, which was critical, as the mechanism needed enough power to shrink and stretch sheet metal effectively. Another key requirement was that the design had to use standard shrinker/stretcher jaws from existing machines. This ensured the tooling would be readily available and avoided the need to modify or manufacture custom jaw components.
With these requirements established, the first concept was developed. The new jaws would act as the interface between the pneumatic tool and the standard shrinker/stretcher tooling, making them one of the most critical components of the design. Using standard shrinker/stretcher jaws meant that the thread, jaw spacing and overall geometry were already defined, while the stroke of the jaws was dictated by the existing pneumatic tool. These fixed parameters formed the foundation of the design and left little room for adjustment.
The design secures one jaw to the body of the pneumatic tool, while the opposing jaw is actuated to apply the shrinking or stretching force. Careful consideration was given to the geometry of the jaws to ensure the tooling remained aligned throughout its full stroke. Maintaining this alignment was essential to achieving consistent forming performance while preventing unnecessary wear on the tooling.
As the tool was intended for daily workshop use, steel was selected for the main jaw bodies to maximise strength, stiffness and long-term durability. Close manufacturing tolerances were specified between the two jaws to minimise play, reduce flex under load and maintain accurate alignment of the tooling. The result is a robust mechanism capable of reliably transmitting the force generated by the pneumatic tool while remaining compatible with readily available, off-the-shelf shrinker and stretcher jaws.
With the design finalised, a complete set of technical drawings was produced and released for manufacturing. Creating accurate technical drawings is a critical stage of the product development process, as they define every dimension, tolerance and manufacturing requirement needed to ensure the parts are produced exactly as intended. This becomes even more important when working with external suppliers, where the drawing is the primary means of communicating the design intent.
The drawings were then sent to a machining supplier to manufacture the two jaws. The design was developed to use readily available standard hardware, reducing the number of custom components, simplifying assembly and helping to minimise manufacturing costs.
Once the machined jaws were received, the first prototype could be assembled. This allowed the complete mechanism to be tested, verifying the fit of the components, the alignment of the jaws and the overall functionality of the design before progressing to the next stage of development.
The first prototype was assembled and tested in-house before being sent to Matt for further evaluation in a real workshop environment. This stage of the development process was invaluable, as it allowed us to validate the design under real-world conditions and identify areas where the tool could be improved in terms of usability, maintenance and overall performance.
Based on the testing, the following improvements were made:
A cut-out was added to the jaws to make changing between shrinking and stretching jaws quicker and easier.
The spring force was increased to provide greater pressure, ensuring the jaws opened more positively after each operation.
The throat depth of the jaws was extended to improve access to mounting bolts and allow deeper insertion of the workpiece.
Spacer shims were introduced beneath the inserts, allowing the tool to accommodate different sheet metal thicknesses.
Holder added for use in a vice.
Building and testing the prototype highlighted both the strengths of the original design and several opportunities for refinement that would not have been apparent during the CAD phase alone. Once these changes had been incorporated into the design, the updated drawings were released for manufacture of the final production-ready version.
This project demonstrates what can be achieved through close collaboration, combining an idea from the workshop with engineering and product development to create a practical, production-ready solution. From the initial concept through design, technical drawings, prototyping and testing, every stage was refined through continuous feedback to ensure the final product met the demands of real-world fabrication.
A special thank you to Matt from Hype Customs for the opportunity to work together on this project and for the valuable input throughout the development process. It was a pleasure bringing this idea to life.
The video below shows the finished handheld shrinker/stretcher in action. If you're interested in purchasing one, the tool is now available for pre-sale through Hype Customs. You can find the link: https://hypecustomsandclassics.com/products/handheld-pneumatic-shrinker-stretcher-tool?variant=48814292828312