From here in the US, we can't really address the quality of and customer relationship with Brazilian machine shops.
However, in the US, there are production shops and job shops who are always competing on price. If we're getting into measuring tenths and arguing with the machinist as to whose measurement is correct, it's a problem and most of them will tell a customer up front they don't offer that quality of service. They're doing "good enough." If one goes to the OEM specifications, there are always several ten-thousandths of an inch even on something as small and tight as a valve stem to guide. On cylinder bores and crankshafts, the allowable variance is thousandths (.001"), not tenths of thousandths (.0001").
However, when building a max performance engine and desiring all clearances to be held within specified tenths, expect to travel farther, take longer and pay more. Speed costs money. How fast can you afford to go?
A performance machine shop here in the US will rightly not appreciate a customer who used a micrometer to set his $100 Fowler dial bore gauge once a month coming back to question the machinist who is using his $2500 Sunnen every five minutes and who for the bore job just set it using a $1500 Sunnen bench comparator.
One tactic which might work is if one really wants to learn to use a dial bore gauge, ask to drop your gauge off with the block and have it set on the same bench comparator the machinist is using for your bore job. Just knowing the checking will be occurring is not a bad thing.
My machinist supplies core engines to a large downtown production house, so he's in there every week watching their processes. Because it's piece-work, they run their hones at max effort. This heats the block. When the block cools, the bores are still going to be within the allowable range, but not really round and really straight. An engine might be in and out in the same day.
In his own shop, he'll take weeks longer, cost twice as much and is fifty miles further out.
But using the same type hone, my guy takes three times as long to hone a block, leaves the last few tenths, lets the block completely cool, then finishes to exact spec.
He loses a lot of quotes from those only looking for cheapest. He'll always have my business because he's the best I've ever seen.
Bottom line - find the good machinists and pay for their quality. Checking is always good, but avoiding an argument over ruined parts is better.
jack vines