Buying stainless steel rod oversize, then turning and grinding, is cheaper (even with the labor) than buying the rod already Turned Ground and Polished (TGP). We're talking small quanitities here, since I work for a small machine shop that does repair work.
A particular piece of 316 stainless came in at ~2.625" Outside Diameter, as drawn (drawn through a die to make it round, not drawn as in on a a piece of paper). It was taken to the Machining area and pre-machined to ~2.500" O.D., then routed to the Polishing Department to polish for chrome plating. We have 0.002" of hard chrome applied to the surface. They call it "two thousandths per side". Try arguing with the plating tech about how a cylindrical object only has one side, the outside. What they mean is that by putting 0.002" onto the outside surface, you add 0.004" to the Outside Diameter (hence "two per side"). So the pre-turned rod had to be ground to 2.5945" to 2.5950" to finish after plating at 2.9990", giving it one thousandth of an inch of slip clearance into the counterbore. I love writing technical junk!
If you're still with me, here's the scenario:
I am looking at the polished-for-plating rod, wrapped in kraft paper and stretch-wrap, on which the grinding technician (We'll call him "Squint") has written in fat black permanent marker: 2.522" .
ME: Hey Squint, didn't this rod get brought to you from Machining?
SQUINT: Yeah. Boss said take four thousandths off it and then get a final measurement.
ME: How can it now be bigger than it was when it was taken out of the lathe?
ME: Um, did you use calipers or micrometers?
SQUINT: I mic'd it.
ME: Can you please unwrap this and do it again?
( Resistance interlude, after which Squint sets the mic but hands it to me. The mic reads 2.4960". )
ME (handing the mic back to Squint): What does that mic read?
SQUINT (gradually extends his hands with the micrometer farther and farther from his face, and walking over to right in front of a 500W job light, while making his eponymous facial expression): Um...
ME: Dude, you need glasses!
SQUINT: No I don't!
ME: You need to have your eyes checked, or at least buy a pair of reading glasses! You can't even read the mics! You're 50 years old! It happens to everybody!
SQUINT: No, they said I don't need glasses.
ME: You had your eyes checked?
SQUINT: Yeah, they said they were fine and I don't need glasses.
ME: You went to the eye doctor, and the eye doctor asked you to read something like I just did, and he said you don't need vision correction?!
SQUINT: Yeah, they said I don't need glasses.
ME: You've been malpracticed, man! Who did you go to? We have Kaiser coverage. You're saying a Kaiser doctor...
ME: Well? Where did you have you eyes checked?
SQUINT: At the Department of Motor Vehicles when I renewed my license!
ME (NOT out loud): I am so totally blogging this!
* * *
This is what we're up against.
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