Close tolerance spun parts are essential for industries where precision fit, reliable performance, and repeatable quality are non-negotiable. While most spin shops can achieve diameter tolerances of ±0.015” (±0.4 mm), it is possible to hold even closer tolerances on specific part features. For parts ranging from 5” to 24” in diameter, tolerances as tight as ±0.005” (±0.12 mm) can be achieved when the process and tooling are optimized.
These capabilities make close tolerance spun parts ideal for applications such as bearing seals, protective guards and covers for rotating equipment, slip-fit cylindrical components, and mating assemblies across industries like:
- Agricultural and mining equipment
- Large engines and rail systems
- Axle and powertrain assemblies
- Food and industrial processing equipment
Material Thickness Considerations
In the metal spinning process, the wall thickness of a part typically reduces during forming. This means that spun parts generally start with a wall thickness greater than the intended finished thickness. When adding machining steps, this must be considered because machining will remove additional material.
The process works best for parts with a finished wall thickness of 0.070” to 0.150” — providing good stiffness and minimal out-of-round conditions. To achieve this, the starting wall thickness may range from 0.135” to 0.250”. While it is possible to machine thinner-walled parts, the design must account for maintaining circumferential tolerances.
OD Machined Features
For outside diameter (OD) features, precision machining can be integrated into the spin forming sequence. At Church Metal Spinning, our Leifeld spinning lathes use a six-tool carousel, allowing different forming rollers and cutting tools to be accessed in a single part program.
By machining the part while it remains in place against the forming tooling, the workpiece stays fully supported and centered. This results in excellent concentricity and stable, consistent cuts. With this approach, finished diameters with tolerances of ±0.005” can be achieved.
ID Machined Features
Inside diameter (ID) features require a separate machining operation because they are formed against the tooling and cannot be accessed during the spin forming sequence. For these operations, we use our Trak CNC tool room lathe with part-specific soft jaws to hold the workpiece securely.
Care is taken to ensure that the chuck does not squeeze the part out of round. The combination of dedicated soft jaws and the repeatability of programmable CNC machining ensures accurate and repeatable results.
The Advantage of Close Tolerance Spun Parts
Close tolerance spun parts with machined features offer a winning combination of the strength and seamlessness of metal spinning with the precision of CNC machining. This hybrid approach reduces the need for secondary operations, improves part accuracy, and helps ensure a perfect fit in critical assemblies.
Whether you need a slip-fit cylindrical part, a precisely machined cover, or a custom guard for industrial equipment, close tolerance spun parts deliver the precision and performance your project demands.
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