What Tolerances Should I Specify, and How Do Tighter Tolerances Change the Cost?

Direct answer: Set tolerances by functional need: keep general features at a suitable default and tighten only the dimensions that control fit, interface, movement, sealing, or safety. A tighter callout can increase process work, tooling or setup effort, measurement time, and inspection cost, so confirm the requirement from the drawing.

How tolerance setting changes cost

Cost can change when a tolerance requires a different process route, additional setup or tooling control, slower handling, more frequent checks, or more detailed inspection records. The effect depends on material, thickness, geometry, quantity, and the agreed acceptance method.

What to separate on the drawing

Separate general tolerances from functional and critical callouts. Identify datums, mating features, holes, bend locations, and inspection methods so the supplier can review the requirement against the part’s function.

FAQ

Should every dimension use the tightest tolerance? No. Reserve tighter requirements for features where function or fit requires them.

What makes a tolerance expensive? The process, setup, tooling, handling, measurement, sampling, and records needed to demonstrate the requirement can all affect cost.

What should I send for a tolerance review? Send the drawing revision, material, thickness, quantity, functional features, finish, and inspection requirements.

For the method, see the three-tier tolerance and DFM method and the key tolerance selection guide. For project review, use the contact page.

Sheet metal tolerances and cost move together. Specify tolerances only where the part function needs them. Laser cutting typically holds around ±0.1 mm on standard sheet thicknesses. Stamped and bent dimensions depend on material and tooling. General tolerances cover most features. Tighter callouts add cost because they slow production and add inspection.

Cost structure also shapes how money should move between you and a China supplier — see payment terms for metal parts from China.

Match each tolerance to its function. A mounting hole may need tight control. An outer edge may not. Ask your engineer which dimensions really matter. The drawing should carry a clear general tolerance block plus critical callouts. Xinjiuxinji confirms achievable tolerances for your specific features in a free DFM review before quoting. We then verify them through first-article inspection. Send your drawing to tylor@xinjiuxinji.com.