DEMO — fictional range. Local brief only, NOT SENT. No personal data is collected or transmitted.
GUIDE
The order the questions are worth asking in.
This is the sequence a machining programme follows when it goes well, and the point at which each step becomes expensive to revisit.
- 1 · Intended use
- What the part does, and what happens if it fails
- 2 · Material
- Chosen for the load and the environment, then for machinability
- 3 · Features
- Which dimensions locate, which carry load, which are only clearance
- 4 · Tolerance
- Set from the first three, not copied from an earlier drawing
- 5 · Finish
- Chosen for what the surface resists, and recorded with the tolerance
- 6 · Process
- Chosen for the features it can hold in one setup
- 7 · Inspection
- What is measured, by whom, when, and what happens if it fails
- 8 · Revision
- Every change lettered, dated and attributed
Why the order matters.
Each step constrains the next. Choosing a process before the tolerance is choosing a process for a part nobody has specified, and choosing a finish before the tolerance is deciding which of the two gets measured without saying so.
Where programmes usually go wrong.
Step four, copied from a previous drawing. It is the cheapest step to do properly and the most expensive one to inherit.