A tighter number can change how the part is made
Holding a feature tighter can mean a slower, more careful setup, different tooling, extra finishing steps, or a better-suited machine.
It can also shrink the list of shops that are a good fit for the job.
Checking the part costs money too
A tolerance only means something if someone measures it. Critical dimensions can need extra inspection time, special gauges or formal reports.
Mark which features are truly critical so the inspection effort goes where it matters.
Features affect each other
Dimensions don't live alone. How features relate to each other, which surfaces they are measured from, and how parts stack up in an assembly can make a simple-looking part hard to hold.
A design-for-manufacturing review helps when a drawing calls out several tight requirements that may overlap or be hard to check the same way every time.
Don't tighten everything by default
A tight general tolerance on every feature adds machining and inspection work without making the part work better.
Instead, find the features that control fit, sealing, motion or alignment, and keep the tight numbers there.
- Fits with mating parts
- Sealing surfaces
- Bearing and motion surfaces
- Alignment and locating features
Your engineer still makes the call
Any tolerance change needs approval from whoever owns the design. A manufacturing review can point out what is driving the cost. It should never quietly change the design.