If you are a designer this section is for you. Be sure to identify critical point of tolerances, don’t just give an overall dimension on your drawing. The ability to hold tight tolerances for short runs is a specialty of metal spinning. This is not always cost ffective.
Generally, the tolerances that can be held directly affects the cost of the part. Tolerances of +- 0.030” (0.76mm) are normal for most sizes, diameters and materials. If requires, +-0.005” (0.13mm) or better may be possible.
Specify and Internal Diameter if Possible. It is best to specify and ID tolerance for your spun parts. If an outside diameter (OD) tolerance is given, material thin out of up to 25% would be typical.
Material thickness. The thickness of the sidewall and bottom of the spun part will vary, normally up to 25 percent. The bottom of the part stays at the thickness of the original blank, while the sidewall thins depending on pressure and speed of forming.
If uniform wall thickness is critical, be sure it is specified. Secondary machining may be necessary in some cases. If you need specific thickness or dimension on the part of a sidewall, do not specify it on the whole part.