Tighter tolerances = Exploding costs?

Here’s how to spec them SMART in CNC machining and save your budget!

The real budget-killer on engineering drawings isn’t exotic materials - it’s those microscopic tolerances that turn a 2-hour job into a 2-day nightmare. But what if you could slash cycle times 30-50% just by being strategically loose? Here’s our battle-tested playbook for designers and manufacturing engineers:

Function > Perfection
Clamp down only on mating surfaces, datum holes, or load-bearing features. Everything else? Let it breathe at ±0.1mm (or looser!).

Know your shop’s limits
Most 3-axis CNC laugh at ±0.005mm. Push part ±0.002mm and you’re begging for secondary ops + 100% inspection. Ask: “Can this be done in ONE setup?”

The 1:10:100 Rule
• ±0.1mm = standard rates
• ±0.01mm = 2-3x cost
• ±0.001mm = 5-10x  cost + custom tooling
(Yes, one zero can 10x your quote)

The #1 hack nobody talks about:
Loop in your machinist at the sketching stage.
Share the 3D model + intended function. 9/10 times they’ll say: “Relax this shoulder to ±0.05mm and we’ll hit it in one op.”

What’s the tightest tolerance you’ve EVER held in production - and was it actually necessary? I believe you have your own horrible stories.