Point being that a single spline on a steering column isn’t very big either but makes a big difference when factored in at the rim of the steering wheel when moved one spline.
To each their own, but I’d rather know what I was dealing with from the start rather than be told after 15k miles on new tires that the cause of tire noise and/or irregular tread wear such as feather edging is due to the toe being off a little. Guess I’m just too proactive because I’d rather know something before rather than later.
Net build alignment cars have been built by all automakers for 25 years plus. Consider cars with struts with NO mechanism for alignment except for toe. The cars come off the assembly line at 75 per hour with no adjustment for camber or caster and life is good until you bend something. It works because the attachment points are far apart. 0.030 inches error at 22 inches away is nothing like 0.030 inches at 8 inches way - the upper control arm on a double a-arm design.
And building body shells to 0.030 accuracy is very hard. In the past some critical holes were pierced AFTER body weld to get that accuracy. New techniques for stamping and welding help that a lot but 0.003 is far too much to ask for a single stamped part let alone a welded body shell.
To me, that begs the question of how accurate is an alignment going to be if .030 is considered allowable?
I don’t really see that as a problem. They’re cars, they’re dynamic, they move and turn and bend. I would imagine my 250lb butt in the seat could cause .030 flex and give in the floor pan, not to mention the alignment angles, and I’d expect much more banging over speed bumps and driveways. They’re not space shuttles, they’re just cars.
Overall size has to be considered when evaluating tolerances.
.0005 variation of a 4" cylinder bore is one part in 8000, 0.0125%.
.030 in a 48" frame section is one part in 1600, 0.0625%
So .030 seems big but it’s really not.
All manufacturers have default tolerances that depend on the size of the measurement. OK did not specify what the 0.03" tolerance was in reference too. I’m sure on the floor pan, there are a lot of measurements to be taken. But on every drawing used in manufacturing, there is a tolerance table that shows the allowable tolerance for dimensions based on size range.
The tolerance table may be done in different ways, for example it may say something like not specified +/- 1%, critical +/- 0.1% etc or it might be >10" +/- 0.3", >1<10" +/- 0.03" etc. The length of the floor pan, which is a lot more than 10", a 0.03" tolerance would be overkill, but a 1/4 diameter hole, you would want a much tighter allowance. The location of the hole might be 5 or six inches away from one of the built in reference points so 0.03" might be OK, unless that dimension is determined to be critical, then it may have a tighter tolerance.
You can’t really judge whether the tolerance is appropriate without knowing what the design dimension is.