The average human hair measures between .003” and .006”. Now picture a 50” OD with a +/-.001 tolerance. Impressive, correct? Now consider that a 5 degree temperature difference between the part and the piece of inspection equipment used to measure it would throw off the reading by about .0015.
That’s an inaccuracy of 75% of the total tolerance of the OD in question. Was the gage properly calibrated? Did the finish meet specifications? Are all ODs and IDs properly centered and within the roundness specs? What amount a taper is acceptable for your project? When you start closely looking at all the variables that go into producing quality features on a large diameter turning job, the precision needed to fulfill tight tolerances at those sizes becomes increasing more complex.
Finding a partner you can trust to properly handle your large diameter turning projects presents plenty of opportunities for regret or success. Does the shop you’re looking at focus on all aspects of precision and quality inspection methods? Do they have the correct equipment to safely, consistently, and effectively produce the project you need?
The list of challenges that a machinist faces when working on a large turning job is extensive. It is an obvious but often overlooked aspect of large diameter turning that tool life issues are going to arise. The amount of minimum cut time on one edge of an insert is exponentially larger than that same insert being used to run a small part, high production job. Finding a company that is equipped to safely handle your large part from receiving to shipping, and every step in between, requires research and should be approached with the due diligence that your large project commands.