You can turn them off the truck. The quality of the job is controlled by the person doing the machine work.
Also turned on the truck is no sign that it will come out true eather. The same apply's here also. The person doing the work makes or breaks the quality of the job done.
The bottom line is when you are looking for some place to do the work find out how long the machinist has been doing this type of work. Little time on job. Find another place to take it to.