Part
Stepped spindle shaft
Three diameters turned from bar with a keyway flat and a threaded nose. Concentricity between the bearing seats is the whole specification.
Open the part →DEMO — fictional range. Local brief only, NOT SENT. No personal data is collected or transmitted.
PRECISION MACHINING / FICTIONAL RANGE
Every dimension is measured from somewhere. Say where.
PLANAXIS is a fictional machining range covering stepped shafts, milled housings and drilled mounting plates. The site is organised around the datum rather than around the catalogue: which feature everything else is measured from, and what happens when that is left unsaid.
Three parts, three datums.
Each part in this range is built from a different reference, and choosing the wrong one is the mistake that survives every inspection until assembly.
Part
Milled housing
A pocketed housing with a through bore and four mounting holes. The pocket floor and the bore axis are what the assembly is built from.
Open the part →Part
Drilled mounting plate
A flat plate with a six-hole pattern and a raised bronze boss. Position of the pattern against the boss is the only dimension that matters.
Open the part →What a drawing leaves unsaid.
Four things a supplier has to assume unless the drawing states them. Each is cheap to write down and expensive to discover.
- The datum
- Which feature every other dimension is measured from
- The critical feature
- Which dimension the assembly actually depends on
- The setup count
- How many times the part is re-clamped, and therefore how many datums it accumulates
- The measurement
- How the critical feature will be checked, and with what
Why the datum comes first.
Because every other dimension is measured from it. A drawing that does not name one leaves the choice to the shop, and two shops will make two different parts that both pass inspection against their own reference.
What this site cannot tell you.
Whether a part will survive its real load. That is a physical property, established by measuring a physical part against a written specification.