Spin shops regularly produce spun parts with diameter tolerances of +/-0.015” (+/-0.4mm); however, holding even closer tolerances is possible on specified part features. When done by the experts, parts from 5” to 24” in diameter, holding specific feature dimensions to +/-0.005” (+/-.12mm) is possible.
Industrial applications that may benefit from these feature dimensions include:
- Bearing seals
- Guards/covers that protect rotating items
- Covers/cylindrical shapes that require a slip fit with mating components.
Industries that may require this style of part include agricultural and mining equipment, large engine or rail applications, axle or power train, food or industrial processing equipment.
Material Thickness
Generally, spun parts will thin during the spin forming operation, thus, a spun part will generally begin with thicker than targeted ending wall thickness. Similarly, the desired finished thickness must be considered when adding a machining step that will further reduce thickness. The process works best on parts with a finished wall thickness of 0.070” to 0.150” as the formed shape has good stiffness and minimal out of round. A starting wall thickness of 0.135” to 0.250” may be required to meet the finished wall thickness requirement. It is possible to machine thinner walled parts with the expectation that they will meet tolerance circumferentially.
OD Features
As part of the spin program, after completion of the forming process, a cutting tool is applied to the targeted machined features. Our Leifeld spinning lathes have a six-tool carousel so that different forming rollers and cutting tools can be accessed within the part program. By machining the part in place against the tooling, the part remains fully supported and on center during the machining operation promoting concentric stable cuts. Finished diameters with tolerance of +/-0.005” can be achieved with excellent concentricity.
ID Features
As the ID features are spun up against the tooling and are not accessible in the spin forming sequence, an additional operation is required. Church Metal uses our Trak CNC tool room lathe to complete the machined features using part specific soft jaws to hold the part. Caution must be exercised to confirm that the part is not being squeezed out of round by the lathe chuck. The dedicated soft jaws coupled with the excellent repeatability of our programmable Trak tool room lathe produces an excellent outcome.
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